of Climate Change in Mesoamerica

Technical Series
Technical Report No. 383
ABC
of Climate Change
in Mesoamerica
Miguel Cifuentes Jara
Tropical Agriculture Research and higher Education Center (CATIE)
Climate Change Program
Turrialba, Costa Rica, 2010
The Tropical Agricultural Research and Higher Education Center (CATIE) is a
regional center dedicated to research and graduate education in agriculture and the
management, conservation and sustainable use of natural resources. Its members
include the Inter-American Institute for Cooperation on Agriculture (IICA), Belize,
Bolivia, Colombia, Costa Rica, the Dominican Republic, El Salvador, Guatemala,
Honduras, Mexico, Nicaragua, Panama, Paraguay, Venezuela and Spain.
© Tropical Agriculture Research and higher Education Center, CATIE, 2010
ISBN 978-9977-57-529-2
Credits
Technical editors
Enric Aguilar, Ph.D.
Climate Change Research Group
Geography Department
University Rovira i Virgili de Tarragona
Av. Catalunya, 35
43002, Tarragona
Spain
Víctor Orlando Magaña Rueda, Ph.D.
Center for Atmospheric Sciences
Universidad Nacional Autónoma de México
Ciudad Universitaria
Mexico City 04510
Mexico
Editor
Elizabeth Mora
Copy editors
Joselyne Hoffmann
Cynthia Mora
Designer
Rocío Jiménez Salas
Translator
Christina Feeny
Contents
Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 5
Key concepts of global climate change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Climate and the greenhouse effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 7
Climate change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 8
Natural climate variability . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Planetary movements . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 9
Solar radiation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 10
Volcanic eruptions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Human influence on climate . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Greenhouse gases (GHG) . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 11
Aerosols . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 13
The unequivocal human action . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 14
Evidence of climate change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 16
Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 17
Changes in the oceans . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 18
Ice and snow cover . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Extreme events . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 19
Climate scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 21
IPCC carbon emissions scenarios . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 22
The importance of considering several scenarios . . . . . . . . . . . . . . . . 24
Projections of future climate change . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 24
Areas of uncertainty in the predictions . . . . . . . . . . . . . . . . . . . . . . . . . . . 26
Climate in Mesoamerica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Historical climate patterns . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
Precipitation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 29
3
ABC of Climate Change in Mesoamerica
Temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Changes observed in climate variables . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Climate scenarios for Mesoamerica . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .
Expected changes in temperature and precipitation . . . . . . . . . . . . . . . . .
31
31
35
36
Effects of climate change on Mesoamerica . . . . . . . . . . . . . . . . . . . . . . . . . . 41
Water resources . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 44
Biodiversity . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 45
Climate change severity index . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 48
Terrestrial ecosystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 49
Aquatic ecosystems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Freshwater systems . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 52
Mangrove forests and coral reefs . . . . . . . . . . . . . . . . . . . . . . . . . . . . 53
Coastal zones . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 54
Fisheries . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 55
Agriculture and cattle ranching . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Generalities of the sector . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 56
Changes in production . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 57
Human health . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .59
Disasters . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 60
Other sectors . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 62
Bibliography . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 63
Annex 1 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .73
Annex 2 . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . .80
4
Introduction
Introduction
Human activities have brought about changes in the natural functioning of the Earth’s climate system. Potential effects are varied and
affect all areas of human endeavor. The scale of the changes and a
limited capacity for response make Mesoamerica the region most
vulnerable to climate change in the entire tropical region. In the face
of this threat, it is essential to have access to high quality information to better understand the scope of the potential effects of climate
change and design strategies to address them.
The purpose of this document is to provide up-to-date scientific
information to support the formulation of the Regional Strategy on
Climate Change for Central America and the Dominican Republic.
The strategy aims to guide the actions of different sectors, institutions
and organizations (governmental, private and civil society) to respond
more effectively to the impacts and challenges of climate change. It
will also help the countries of the region to position themselves in the
global process of discussion and negotiation on climate change.
This document consists of three main parts. The first contains a detailed
description of the processes that generate climate on Earth, the role
played by human activities in influencing climate, the scientific evidence related to climate change and an analysis of climate scenarios.
The second part of the document contains a summary of historical climate patterns in the region, the changes observed in recent decades
and the predictions for future climate. The third section offers a synthesis of the potential impacts of climate change on those sectors of society
which, according to the Intergovernmental Panel on Climate Change
(IPCC), would be most affected by climate change.
5
Key concepts of global climate change
1
Key concepts of global climate change
Climate and the greenhouse effect
Climate is defined as the set of states and changes in atmospheric
conditions observed in a given area over a period of at least 30 years.
Average conditions, together with their variability, and extreme
events of precipitation, temperature, wind, atmospheric pressure, etc.
are all expressions of a region’s climate. The climate of an area is a
dynamic phenomenon subject to variability and change.
Solar radiation is the main source of energy for the planet’s climate
system. More specifically, the balance (known as “radiative balance”)
between the energy received by our planet from the sun, and energy
that it re-emits, is the main mechanism that determines the Earth’s
climate. To balance the amount of incoming energy absorbed, the
Earth must radiate approximately the same amount of energy back
to space. This occurs in the form of long wave energy, also known as
thermal radiation. Approximately 30% of the solar energy reaching
our planet is reflected directly back into space by the highest layers
of the atmosphere and by surfaces with a high albedo1, such as those
covered with ice and snow. The remaining two-thirds of the incident
energy are absorbed by Earth’s surface and by the atmosphere.
Some trace gases in the atmosphere (carbon dioxide, methane, among
others) absorb a large amount of thermal radiation emitted by the
surface of the planet and radiate it back to Earth again. This natural
1 Albedo is a fraction of solar radiation reflected by a surface or an object, often
expressed as a percentage.
7
ABC of Climate Change in Mesoamerica
phenomenon is known as the “greenhouse effect” and results in the
warming of the planet’s surface (Figure 1). If the natural greenhouse
effect were not in place, the temperature of Earth’s surface would be
-18 ºC and would fluctuate widely between day and night. Therefore,
the natural greenhouse effect makes life as we know it possible on
Earth.
Atmospheric trace gases that directly contribute to the greenhouse
effect are commonly known as “greenhouse gases” or “GHG”. The
main greenhouses gases that contribute to global warming are water
vapor and carbon dioxide (CO2). Other important GHG are methane
(CH4), nitrous oxide (N2O), ozone (O3), among others. Human activities have increased the concentrations of carbon dioxide, methane,
chlorofluorocarbons, etc. in the atmosphere, further intensifying the
greenhouse effect and thereby increasing Earth’s surface temperature.
Climate change
The climate system changes over time under the influence of its own
internal mechanisms (such as El Niño/Southern Oscillation) and also
because of external factors known as natural drivers or “forcings”.
Some of the most important external natural forcings affecting climate are variations in solar activity, planetary movements, volcanic
eruptions and changes in the composition of the atmosphere.
Recently, scientists have determined that human activities—more
specifically, increases in concentrations of greenhouse gases in the
atmosphere—have become a dominant external forcing on the climate, being responsible for most of the warming observed in the last 50
years. This phenomenon, is popularly known as “global warming”, or
more broadly as “climate change” when other effects are considered.
The IPCC definition of “climate change” does not distinguish between
natural and anthropogenic causes of climate change, whereas the
8
Key concepts of global climate change
Figure 1. Idealized model of the greenhouse effect. From Solomon et al.
(2007).
definition of the United Nations Framework Convention on Climate
Change (1992) describes this process as “a change of climate which is
attributed directly or indirectly to human activity that alters the composition of the global atmosphere and which is in addition to natural
climate variability over comparable time periods.”
Natural climate variability
Planetary movements
Long before human presence on Earth, the planet’s energy balance,
and therefore its climate, was affected by various natural causes. For
example, there is strong evidence showing that ice ages occur periodically and that these are linked to variations in Earth’s orbit. These
changes are known as “Milankovitch cycles” (Figure 2), which are
regular variations (in the order of hundreds of thousands of years)
in the eccentricity of Earth’s orbit around the Sun, and changes in
9
ABC of Climate Change in Mesoamerica
Earth’s obliquity2 and precession3. Such variations in the planet’s
movements alter the amount of incoming solar radiation received
by the planet at different latitudes, producing drastic changes in the
global climate.
Solar radiation
Another likely cause of climate change is the variation in the amount
of energy produced by the Sun. For example, sunspot observations as
well as data from isotopes generated by cosmic radiation, show that
solar radiation varies (by nearly 0.1%) in short 11-year cycles and
also over much longer periods.
Figure 2. Diagram of Earth’s orbital changes (Milankovitch cycles) that drive
ice age cycles. T denotes changes in the tilt (or obliquity) of the Earth’s axis
and E refers to changes in the eccentricity of the orbit. P denotes precession,
or changes in the direction of the axis tilt at a given point of the orbit. Taken
from Solomon et al. (2007).
2 Obliquity refers to the tilt of the Earth’s rotational axis, with respect to the plane
of its orbit around the Sun.
3 Precession refers to the oscillatory movement, around its axis, exhibited by a
rotating body.
10
Key concepts of global climate change
However, the impact of these periodic changes in solar radiation is
still unknown. In theory, changes in solar activity directly affect the
climate by altering the amount of energy reaching the planet. Solar
radiation also affects the concentrations of some greenhouse gases,
such as stratospheric ozone.
Volcanic eruptions
Catastrophic volcanic eruptions have the capacity to reduce global
temperature. When an explosive volcanic eruption occurs, enormous quantities of ash, dust and sulfate aerosols are expelled into
the stratosphere. These materials form a kind of natural barrier or
shield that reflects solar radiation back to space before it reaches
the planet’s surface, causing temperatures to decrease. However, this
cooling effect is of short duration (2 to 3 years), as was the case after
the eruptions of Mount Agung in Bali in 1963, Chichón Volcano in
Mexico in 1983, and Mount Pinatubo in the Philippines in 1991.
Even the soot expelled by the burning oil wells in Kuwait appears
to have reduced the amount of solar radiation reaching the Earth’s
surface at that time. As a result, the planet’s temperature decreased
slightly for a few months.
Human influence on climate
Climate changes produced by humans are mainly the result of
increases in concentrations of greenhouse gases in the atmosphere
(Figure 3), and of changes in the amounts of aerosols (small particles) that float in the atmosphere. These changes are capable of
altering the planet’s energy balance and increasing or decreasing the
temperature.
Greenhouse gases (GHG)
Human activity results in the emission of several greenhouse gases
(GHG), the most important being carbon dioxide (CO2), methane
(CH4), nitrous oxide (N2O) and halocarbons (gases that contain
fluorine, chlorine and bromine). The amount of GHG produced by
11
ABC of Climate Change in Mesoamerica
human activities increased by 70% between 1970 and 2004. Current
atmospheric concentrations of CO2, CH4 and N2O greatly exceed
pre-industrial values. In 2005, concentrations of CO2 and CH4 greatly
exceeded the natural range over the last 650,000 years. Higher concentrations of these gases in the atmosphere result in an increase in
temperature.
Carbon dioxide is the most important greenhouse gas due to the
enormous amounts of it released into the atmosphere. Since the start
of the industrial revolution and the development of an economy
based on fossil fuels burning, and up to 1970, CO2 has increased by
100 ppmv (parts per million by volume). Between 1970 and 2004,
annual CO2 emissions increased by 80%. Approximately 75% of
the CO2 increase is attributed to the use of fossil fuels (mainly in
the transport sector) and to cement production. The remaining CO2
comes from deforestation and land use changes, which also release
CO2 and decrease the amount of this gas that could be sequestered
by forests. The current rates of increase in carbon dioxide (along with
those of nitrous oxide and methane) are unprecedented, at least in
the last 16,000 years. Current concentrations of CO2 in the atmosphere have reached 384 ppm (parts per million), and show no signs
of decreasing or stabilizing (Figure 3). This value exceeds the range
of the natural variability known in the last 650,000 years.
CH4 is the second most important greenhouse gas. It is released primarily as a result of anaerobic processes in agriculture, the production
of natural gas and waste treatment in landfills. Concentrations of CH4
in the atmosphere have risen from 715 ppm prior to the industrial
revolution, to 1774 ppm in 2005 (Figure 3). N2O is emitted due to fertilizer use and the burning of fossil fuels, although it is also released
through natural processes. Atmospheric N2O increased from 270 to
319 ppm between 1750 and 2005 (Figure 3). Finally, chlorofluorocarbons (CFCs, a type of halocarbons) are completely synthetic gases
introduced by humans, and do not occur naturally.
12
Key concepts of global climate change
Aerosols
Aerosols are very small particles (between 0.07 and 20 μm, depending on their origin) suspended in the atmosphere. Aerosols vary
greatly in terms of their concentration, chemical composition and
size, and may be of natural or anthropogenic origin. The burning of
fossil fuels and biomass has increased the amount of sulfur aerosols,
organic compounds and soot (also called “black carbon”) in the
atmosphere. Mining and other industrial processes release additional
amounts of aerosols and dust. In general, aerosols produce a cooling
of earth’s temperature because they reflect solar radiation. For example, the accelerated industrial development after the Second World
War increased atmospheric pollution in the Northern Hemisphere,
contributing to a decrease in temperature between 1940 and 1970
approximately (Figures 4 and 6).
1750
Figure 3. Concentrations of greenhouse gases in the last 2,000 years.
Increases since 1750 are attributed to human activities during the industrial
era. Concentration units are measured in parts per million (ppm) or parts per
billion (ppb). Adapted from Solomon et al. (2007).
13
ABC of Climate Change in Mesoamerica
The unequivocal human action
It is “very likely” (Annex 2 contains specific definitions regarding
IPCC guidelines on uncertainty) that the increase in atmospheric
greenhouse gases concentrations since the beginning of the industrial age (around 1750) has had a net warming effect on temperature.
Numerous experiments have been carried out using different climate models to determine the probable causes of climate changes
that occurred in the 20th century. The results of these experiments
show that natural forcings (solar radiation, aerosols from volcanic
eruptions, etc.) are not sufficient to explain the trend toward rising temperatures on Earth. These trends can only be replicated by
including human influence in the models (Figure 4).
Furthermore, human influence considerably exceeds the intensity of
any natural forcing that could otherwise control the climate (Figure 5).
It is estimated that even if humans were to drastically reduce their
greenhouse gas emissions, global warming would proceed more rapidly than during the last 10,000 years. This is because the influence of
greenhouse gases on the planet’s energy balance persists during a very
Figure 4. Changes in surface temperature (°C) relative to the 1901-1950
mean value, from one decade to another, from 1906 to 2005. The black line
shows changes in observed temperatures y colored bands show the range
covered by 90% of the simulations from recent models. The red band shows
simulations that include natural and human factors, while the blue bands show
simulations that include only natural factors. Adapted from Solomon et al.
(2007).
14
Key concepts of global climate change
long time. In other words, there is sufficient scientific evidence to affirm
that the global warming observed recently is the result of human action.
Figure 5. Main components of radiative forcing of climate change. Values
represent the forcings in 2005 relative to the start of the industrial era (around
1750). Positive forcings lead to a warming of the climate and negative forcings
to a cooling. Error bars represent the range of uncertainty for each forcing.
Taken from Solomon et al. (2007).
15
ABC of Climate Change in Mesoamerica
Evidence of climate change
The warming of oceans and of the land surface, changes in the distribution and intensity of precipitation, rising sea levels, the melting
of glaciers, the displacement of sea ice in the Arctic and the shrinking snow cover in the Northern Hemisphere are all signs that confirm
the warming of the planet’s surface. However, the observed changes
do not occur uniformly all over the world. For example, due to the
influence of local factors, there are some areas of the world where the
temperature has actually decreased, even though the global average
is increasing. This is consistent with climate trends on a smaller spatial
scale and is not sufficient to negate the warming at global level.
Temperature
Between 1906 and 2005 global surface temperature of the Earth
increased by 0.74 ºC (Figure 6a). Average temperatures in the
Northern Hemisphere during the second half of the 20th century
were likely the highest of the last 1,300 years. However, the increase
has not been uniform around the world, neither in spatial nor in temporal terms. For example, warming has been greater over land than
over the oceans, particularly since the 1970s. Seasonally, warming has
been slightly greater in the winter hemisphere (also called the dark
pole or pole in shadow) and in the high northern latitudes. However,
in some parts of the world, such as the northern part of the North
Atlantic, temperatures have decreased.
During the last century, warming occurred in two phases, with an
accelerating rate in the last 25 years: between 1910 and 1940 the
average global temperature increased by 0.35 ºC, and from the1970s
it rose by 0.55 ºC (Figure 6a). Eleven of the 12 warmest years since
records began have occurred since 1995. Consistent with this warming, a decrease in the number of very cold days and nights has been
observed. Furthermore, the duration of the ice-free season has
increased in most middle and high latitude regions of both hemispheres. In the northern hemisphere, this translates into an earlier
start to spring.
16
Key concepts of global climate change
Precipitation
Precipitation shows greater spatial and temporal variability than
temperature. Changes observed in some regions are dominated by
long-term variations, though trends were not evident during the 20th
century. During this same period, annual precipitation increased
significantly in eastern parts of North and South America, northern
Figure 6. Changes in: a) global average surface temperature; b) global
average sea level and c) Northern Hemisphere snow cover for March-April.
From IPCC (2007).
17
ABC of Climate Change in Mesoamerica
Europe and northern and central Asia. By contrast, the Sahel, the
Mediterranean, southern Africa and parts of south Asia are now
drier than at the start of the 20th century (Figure 7). In northern
regions, precipitation in the form of rain is now more common that
in the form of snow.
Changes in the oceans
Warming has been most evident in parts of the middle and low latitudes, particularly in tropical oceans. Since 1961, the oceans have
absorbed more than 80% of the heat added to the climate system.
This has caused an increase in the average global temperature of
the ocean to a depth of at least 3,000 m, with the consequent rise
in sea level. Thermal expansion of seawater and the melting of ice,
both processes due to the increased global temperatures, contribute
Figure 7. Changes in annual precipitation are not homogeneous around the
world. In general, average precipitation during the 20th century increased in
continents outside the tropics, but decreased in arid regions of Africa and
South America. Yellow circles represent decreases in precipitation and green
circles represent increases. The size of the circle represents the scale (%) of
the change. Adapted from IPCC (2001).
18
Key concepts of global climate change
to rising sea levels. Thermal expansion has contributed 57% to the
observed increase. Retreating glaciers, ice caps, and ice sheets are
responsible for the remaining increase, at an annual rate of 1.2 ± 0.4
mm, between 1993 and 2003.
However, sea level has not risen uniformly around the world due to
variations in the temperature changes in the oceans, the salinity of
the water and oceanic circulation patterns. Sea level has gradually
risen since the end of the nineteenth century, and it continues rising
even more rapidly (Figure 6b). During the 20th century, the average
rate of sea level increase was 1.7 mm per year. It is also likely that the
rate of extreme sea levels has increased around the world since 1975.
Global sea level is projected to continue rising during the 21st century,
and to do so at a faster rate than between 1961 and 2003. Thermal
expansion is projected to contribute most heavily to average sea
level increases for the next 100 years, at least, particularly if greenhouse gas concentrations are not stabilized.
Ice and snow cover
In the northern Hemisphere, springtime snow cover has been declining by 2% per decade since 1966 (Figure 6c). Furthermore, the snow
is melting earlier in spring. There has been a widespread decline in
mountain glaciers and snow cover in both hemispheres, while annual
Artic sea ice extent has been shrinking at an average rate of almost
3% per decade. The decrease in the area of sea ice exceeds 7% per
decade. The area of permafrost and seasonally frozen ground, as well
as the ice in rivers and lakes, has also decreased.
Extreme events
“Extreme events” refer to maximum or minimum values of a particular variable, or to infrequent climatic events of great intensity
(for example, storms, droughts, heat waves). In the last 50 years, the
number of cold nights has decreased and the number of warm nights
has increased. Maximum and minimum temperatures have also
19
ABC of Climate Change in Mesoamerica
increased (Figure 8). The number of frost-free days has increased
as the temperature has risen in middle latitudes. It is likely that heat
waves are now more frequent in most land areas.
It is to be expected that a warmer climate will increase the risk of
drought in places where it does not rain, and increase the risk of
flooding in areas where it does rain. The distribution and timing of
droughts and floods is most profoundly affected by the cycle of El
Niño events, particularly in the tropics and in many parts of the midlatitudes of the Pacific Rim countries.
The intensity of precipitation and the risks of intense rainfall and
snowfall increased during the 20th century due to an approximate 5%
increase in atmospheric water vapor. As a result, during the last 50
years more intense precipitations have been observed in warm climates, even in places where overall annual precipitation is decreasing.
Figure 8. Trends observed (in days per decade) from 1951 to 2003 in the
frequency of extreme temperatures, relative to mean values for period
between 1961 and 1990: a) cold nights, b) cold days, c) warm nights and
d) warm days. The red line shows the decadal variations. Adapted from
Alexander et al. (2006).
20
Key concepts of global climate change
This means that the seasonality of rainfall is now more marked. Very
dry land areas across the globe have more than doubled in extent
since the 1970s, and droughts have become more common in many
regions of the planet.
It is also very likely that even stronger events will occur as overall
levels of precipitation increase. The number of category 4 and 5 hurricanes has increased by about 75% since 1970. The largest increases
have been observed in the North Pacific, Indian and Southwest
Pacific Oceans. In the North Atlantic, the number of hurricanes was
also above average in 9 of the 11 years during the period from 1996
to 2007. However, the detection of long-term trends in cyclonic activity is not yet very reliable.
Climate scenarios
Projections of future climate change have a certain level of uncertainty due to the changing nature of the climate and to the difficulty
in determining future levels of GHG emissions. Concentrations of
GHG depend on many assumptions and factors with varying degrees
of uncertainty, such as population growth, development and use of
alternative energies, technological and economic development, and
human policies and attitudes toward the environment. For these reasons, the different scenarios used contemplate different ranges of
these factors to investigate the potential consequences of anthropogenic climate change.
A climate scenario is defined as a plausible and generally simplified
representation of a possible future climate, based on an understanding of how the climate works and of the different factors that
influence it. Scenarios are typically constructed as input to evaluate the possible impacts of climate change on natural and social
systems.
21
ABC of Climate Change in Mesoamerica
IPCC carbon emissions scenarios
The IPCC Special Report on Emissions Scenarios (SRES; see IPCC,
2000) contains 40 different scenarios, grouped into four families
(Table 1) that explore alternative forms of development. The scenarios incorporate demographic, social, economic, technological,
and environmental factors, together with the resulting greenhouse
gas emissions, to draw some conclusions about future climate change.
The main rationale behind these scenarios is that societies have the
option of either working together to resolve global problems through
joint and comprehensive solutions, or remaining isolated and trying
to resolve their problems independently. Furthermore, development
goals may be aimed at increasing human wealth or at conserving the
environment (Figure 9).
Figure 9. Conceptual framework of IPCC families of climate change
scenarios. The horizontal axis represents ways of adapting to problems while
the vertical axis represents the type of development. Adapted from Palma
Grayeb et al. (2007) and Anderson et al. (2008).
22
Key concepts of global climate change
Table 1.
Family
A1
A2
B1
B2
Characteristics of IPCC families of climate change
scenarios.
Number of
scenarios
Characteristics
17
Rapid economic growth, low rate of population
growth, and rapid shift towards more efficient
technologies. Convergence between regions.
Differences in personal income significantly
reduced. This family is divided into three groups
based on the energy system used: intensive use
use of fossil fuels (A1F), use of non-fossil fuels
(A1T), and balance between different sources
(A1B).
6
A very heterogeneous, self-sufficient world that
maintains local identities. Population growth
rates converge slowly, which results in high
population growth. Per capita economic growth
is slower and more fragmented than in other
families.
9
A convergent world, with low population growth
and rapid changes in economic structures.
Shift toward an economy based on services
and information technology. Less intensive use
of materials, introduction of cleaner and more
efficient technologies. Emphasis on global
solutions to promote environmental, economic
and social sustainability and greater equity.
8
A world emphasizing local solutions to
environmental, social, and economic
sustainability. Population growth and economic
development are moderate. Technological
change is less rapid but more diverse than in B1
and A1. This family focuses on environmental
protection and social equity, but at the regional
and local levels.
Source: IPCC (2000).
23
ABC of Climate Change in Mesoamerica
Other than those already existing, IPCC scenarios do not explicitly
contemplate climate policies that focus directly on reducing greenhouse gas emissions and maximizing the size of CO2 sinks. Instead,
the idea is that the scenarios will serve as a reference for analyzing
the potential consequences of implementing additional policies. All
scenarios are considered equally valid and likely. This leaves the door
open so political discussions regarding possible courses of action in
response to climate change can take place.
The importance of considering several scenarios
Comparing groups of similar models, or making comparisons
between models with different structures, is useful to quantify the
probabilistic aspect of the scenarios. It is also necessary to construct
various future climate scenarios to quantify the uncertainty of the
estimates. In terms of policies, instead of deciding whether a specific
model is most representative of certain future conditions, considering several models enables us to expand our options for developing
a broader range of adaptation alternatives. For this reason, the
IPCC recommends that at least two families of scenarios –with
a wide variety of assumptions– be considered in any analysis of
climate change. In the last simulations of global climate change carried out for IPCC the B1, A1B and A2 scenarios were used. These
are interpreted as possible “low”, “medium” and “high” levels of
emissions. In the Mesoamerican region, the A2 and B2 scenarios
are most commonly used.
Projections of future climate change
If current climate change mitigation policies and sustainable development practices are maintained, greenhouse gas emissions will
continue to increase in the coming decades. As a result, global
warming will intensify during the 21st century, with climate changes
very likely greater than those experienced in the 20th century. The
warming projected for the 21st century would have a geographic distribution similar to that observed until now.
24
Key concepts of global climate change
According to IPCC projections, the global average temperature
increase observed between 1990 and 2005 (0.15 and 0.30 ºC per
decade) will remain approximately the same during the next 20 years.
This trend would not change even if concentrations of all greenhouse
gases and aerosols were to remain at constant levels similar to those
of 2000. Despite the fact that the exact ranges of temperature change
vary slightly between climate scenarios, all IPCC scenarios show
temperature increases (Table 2); up to 6 ºC in the most extreme estimate. It is very unlikely that the temperature increase will be less
than 1.5 ºC.
The extent of the area covered with snow and sea ice will continue
to shrink. It is very likely that extreme temperatures, heat waves
and intense precipitations will become more frequent. It is likely
that future tropical cyclones will be more intense due to higher sea
surface temperature. Trajectories of extra-tropical storms are projected to shift toward the poles. It is very likely that precipitation will
increase in high latitudes, while decreasing by up to 20% in subtropical regions.
Past and future anthropogenic carbon dioxide emissions will continue to contribute to warming and sea level rises for more than a
millennium. Even if all radiative forcings are stabilized and maintained constant by 2100, we would still expect to see an increase
of about 0.5 ºC in global average temperature up to 2200. Thermal
expansion of the oceans would continue for many centuries, due to
the time required to transport heat down to the deepest layers of
the ocean. Sea level rise is projected to reach 0.3 to 0.8 m, relative to
the 1980–1990 level, towards the year 2300 (see Table 2 for estimates
up to 2100). If the Greenland Ice Sheet were to disappear, sea level
would increase by up to 7 m. This value is similar to the sea level estimated for the last interglacial period, some 125,000 years ago.
25
ABC of Climate Change in Mesoamerica
Table 2.
Average range of temperature (ºC) and sea level (m)
increase for the main IPPC climate scenarios.
Temperature
Increase*
Sea level rise
Constant GHG concentrations
Year 2000
0.3 – 0.9
Not available
Scenario B1
1.1 – 2.9
0.18 – 0.38
Scenario A1T
1.4 – 3.8
0.20 – 0.45
Scenario B2
1.4 – 3.8
0.20 – 0.43
Scenario A1B
1.7 – 4.4
0.21 – 0.48
Scenario A2
2.0 – 5.4
0.23 – 0.51
Scenario A1FI
2.4 – 6.4
0.26 – 0.59
Case
* Likely temperature and sea level increases for 2090-2099 relative to 1980-1999.
Adapted from IPCC (2007).
Areas of uncertainty in the predictions
Although our knowledge of the global climate system continues to
expand rapidly and significantly, there are still uncertainties4� regarding some of the observed climate changes. These uncertainties do not
necessarily negate or invalidate the predictions made. It is simply
that there are certain areas of scientific knowledge in which the driving mechanisms are not fully understood. Some of the main areas of
uncertainty are mentioned below.
Analyzing and monitoring observed changes in extreme events
(droughts, hurricanes, frequency and intensity of precipitation, etc.)
is more complex than with average climate patterns, since these
require longer time series and a range of spatial and temporal scales.
The adaptive capacity of some natural and human systems also
makes it difficult to detect the effects of climate change and its driving forces.
4 See Annex 2 for a description of the IPCC’s treatment of uncertainty.
26
Key concepts of global climate change
Although most of the climate change models currently used are
consistent in their simulations of global-level patterns, there are still
difficulties in simulating certain changes (such as precipitation) at
regional levels. At these smaller scales, changes in land use or specific
pollution problems make it more complicated to detect the effects of
anthropogenic warming on natural systems.
The intensity of climate feedback processes such as ocean heat
uptake, the role played by clouds and the carbon cycle have yet to be
quantified with greater certainty. Similarly, the full impacts of aerosols on cloud and precipitation dynamics remain uncertain. The scale
of future sea level rise is still unknown (especially its upper limit) due
to uncertainty surrounding estimates of ice-sheet loss in Greenland
and the Arctic, and the process of heat distribution in the oceans.
27
Climate in Mesoamerica
2 Climate in Mesoamerica
Historical climate patterns
In Mesoamerica, precipitation and temperature exhibit well-defined
annual patterns, modified periodically by fluctuations in the temperature of the surrounding oceans and by the El Niño/La Niña cycles,
the Pacific Decadal Oscillation (PDO). In general, the interactions
between the trade winds from the east and the region’s orographic
complexity determine the differentiated precipitation patterns of
the region’s Caribbean (windward) and Pacific (leeward) slopes. The
effects of the “rain shadow” created by the mountain systems generally mean that the Caribbean slope is rainy practically all year round,
while the Pacific slope is characterized by a prolonged dry season
(Figure 10, compare stations of Limón and Puerto Lempira on the
Atlantic vs. La Unión and Liberia on the Pacific). The southern part
of Central America is rainier than the north.
Precipitation
On the Pacific side of Mesoamerica, precipitation is characterized
by a prolonged dry season lasting approximately from November
until April or May, and a wet season during the rest of the year. The
increased intensity of the trade winds in July produces a peak of precipitation in most parts of the Caribbean slope of Central America
and southern Mexico (Figure 10). Due to prevailing trade winds
from the east in the region, any rise in the surface temperature of
the ocean east of the isthmus causes an increase in precipitation. In
contrast, when the temperature of the ocean’s surface decreases, precipitation declines by up to 40% during the months of July/August
29
ABC of Climate Change in Mesoamerica
(during the mid-summer dry period commonly known as veranillo or
canícula) in the Pacific slope (see the Liberia and Palmar Sur stations
in Figure 10). The veranillo is more pronounced on the western side
of Central America, in the Yucatán Peninsula, and in eastern Mexico.
However, this phenomenon is practically absent in western Mexico,
southern Belize, the south east of Honduras, eastern Nicaragua and
Costa Rica, and the north east of Panama.
Severe droughts on the Pacific coast are associated with the El Niño
phenomenon (an increase in the surface seawater temperature of
the equatorial Pacific that generates anomalies in the planet’s atmospheric circulation). At the same time, masses of cold air from North
America during the winter months, and the trade winds between July
and August, produce intense rains that cause flooding on Central
Figure 10. Topography and monthly precipitation for selected meteorological
stations (location shown with “+”) in Central America and southern Mexico.
Inset graphs show monthly precipitation (vertical bars) for each station. Taken
from Magaña et al. (1999).
30
Climate in Mesoamerica
America’s Caribbean slope. The regions most affected by these conditions are the northern coast of Honduras and the eastern coasts of
Nicaragua, Costa Rica and Panama. The northern coast of Honduras
and Belize are the areas most susceptible to the direct impact of
hurricanes, although the coast of Nicaragua has also suffered their
effects in recent decades.
Temperature
Temperature is strongly related to the temperatures of the Pacific
Ocean, including patterns linked to El Niño events. The temperature regimen is also closely related to the annual precipitation cycle.
Daily temperatures reach their maximum value before the start of
the rainy season and fall around January. Minimum temperatures
show a different pattern: the highest values are observed in July
(when increased cloud cover decreases radiative cooling) and the
lowest values during the Northern Hemisphere winter.
Changes observed in climate variables
Central America is considered to be the main “hot spot” for climate
change in the tropics (Figure 11). An analysis of temperature and
precipitation data from 105 meteorological stations located throughout the Mesoamerican region and in the northern part of South
America (Aguilar et al., 2005) show many changes in the extreme
values of these variables during the last 40 years.
On a regional scale, temperature indices showed significant variations throughout the region during the period between 1961 and 2003
(Table 3). The annual percentage of warm days and nights increased
by 2.5% and 1.7% per decade, respectively. At the same time, the
number of cold nights and cold days decreased by -2.2 and -2.4%
per decade (Table 3). Temperature extremes increased by between
0.2 and 0.3 ºC per decade. The duration of the periods of consecutive
cold days also decreased.
31
ABC of Climate Change in Mesoamerica
Figure 11. The Regional Climate Change Index (RCCI) for 26 land regions
of the world, calculated on the basis of 20 General Circulation Models and 3
IPCC emission scenarios. The size of the circles represents the scale of the
changes in temperature and precipitation indices. Taken from Giorgi (2006).
During the last 45 years, no decrease in annual precipitation has
been observed in the region, though there has been a slight increase
in its intensity. Furthermore, the number of consecutive dry days has
increased. In other words, precipitation patterns have changed so
that now it rains during a shorter period of time, but does so more
intensely, with obvious impacts on agricultural production, soil conservation, floods, water availability, etc.
While most of the meteorological stations analyzed show positive
trends (increased precipitation), overall average annual precipitation
in the region and the number of consecutive wet days do not show
significant changes (Table 3). This is probably due to the limited time
periods covered by the data series and to major annual variations
in precipitation. Furthermore, the heterogeneity of the precipitation
patterns throughout the region (Figure 12) makes it difficult to identify a clear trend for the area as a whole. For example, the number of
32
Climate in Mesoamerica
Table 3.
Trends in regional temperature and precipitation indices for
the period 1961-2003.
Index
Units
Trend
(units/decade)
Temperature
Warm days
% of days
2.5
Warm nights
% of days
1.7
Cold days
% of days
-2.2
Cold nights
% of days
-2.4
Daily temperature range
ºC
0.1
Highest maximum temperature
ºC
0.3
Lowest maximum temperature
ºC
0.3
Highest minimum temperature
ºC
0.2
Lowest minimum temperature
ºC
0.3
Duration of cold period
number of days
-2.2
Duration of hot period
number of days
0.6
Precipitation
Total annual precipitation
mm
8.7
Simple index of daily intensity
mm
0.3
Very wet days
mm
18.1
Extremely wet days
mm
10.3
Maximum precipitation in 1 day
mm
2.6
Maximum precipitation in 5 days
mm
3.5
Days of strong precipitation
number of days
-0.1
Days of very strong precipitation
number of days
0.1
Consecutive dry days
number of days
0.4
Consecutive wet days
number of days
-0.1
Values in bold are statistically significant at 5%. Adapted from Aguilar et al. (2005).
33
ABC of Climate Change in Mesoamerica
consecutive dry days decreased in central and southern parts of the
region, but increased in northern Mexico and the Caribbean.
However, extreme precipitation indices have increased significantly
(Table 3) and are strongly and positively correlated with the temperature of the tropical Atlantic Ocean. The latter indicates that
prolonged rainy seasons are related to the warm waters in that oceanic basin.
The trend over the last 40 years suggests a strengthening of the
hydrological cycle throughout the region, with more rain produced
by extreme events and greater average precipitation per episode.
This trend is expected to continue in the future, possibly resulting
Figure 12. Temporal trends in (a) the percentage of warm days, (b) the
percentage of cold days and (c) total annual precipitation for the period 19712003. Red triangles (with the upward pointing apex) represent an increase,
and blue triangles (with the downward pointing apex) represent a decrease in
the variable. The large triangles represent statistically significant trends, while
the small triangles represent non-significant trends. Adapted from Aguilar et al.
(2005).
34
Climate in Mesoamerica
in a greater frequency or intensity of extreme events (floods and/
or droughts). This does not appear to be linked to El Niño. Despite
the fact that recent hurricanes have caused extensive damage in
the region, it has not been possible to determine with any certainty
whether in future these will become more frequent and intense in
the Caribbean.
Climate scenarios for Mesoamerica
The most recent climate scenarios for the region use data generated
by the Worldclim�5 project (Hijmans et al., 2005). These scenarios
complement the work carried out in the region since the 1990s.
Most of the recent climate models for the isthmus underestimate the
amount of precipitation in Central America (by up to 60%), but consistently replicate the seasonality of the region’s climate, including
the veranillo (Rausher et al., 2008).
Although IPCC models consider a wide range of very complex interactions between aquatic, terrestrial, and atmospheric components,
and their capacity to replicate climate conditions is recognized, their
resolution is not the most appropriate for evaluating the effects at
the regional or country level. For this, it is necessary to reduce the
scale (through a process known as “downscaling”) and increase the
resolution of the data (STARDEX, 2009; Figure 13). The reference
period for climate data is 1961–1990. Changes in temperature and
precipitation were calculated for the time horizons of 2020, 2050 and
2080. These horizons are generic names for the periods 2011–2040,
2041–2060 and 2061–2090, respectively. IPCC B2 and A2 scenarios
(Table 1) were selected as examples of a “favorable” scenario and an
“unfavorable” scenario, respectively. In addition, a “Climate Change
Severity Index” (CCSI) was developed, details of which are included
in the section on effects of climate change in this document.
5 http://www.worldclim.org. Last visit 10/23/2010.
35
ABC of Climate Change in Mesoamerica
Figure 13. “Downscaling” and increase of the spatial resolution (from 400 km
to 12 km) for a temperature change model for Mesoamerica. Adapted from
Anderson et al. (2008).
Expected changes in temperature and precipitation
The global average surface temperature of the planet is expected
to increase between 1.4 and 5.8 ºC up to 2100. Consistent with
this change, temperatures are expected to rise throughout the
Mesoamerican region. However, predictions differ regarding the
scale, direction (increase or reduction) and location of the changes
in precipitation. Despite this uncertainty, in general, the number of
dry days is expected to increase, along with the frequency of more
intense precipitations and extreme events such as storms and floods.
Future climate changes may possibly be due to changes in the surface temperature of the ocean, the displacement of the inter-tropical
convergence zone, the expansion and intensification of the high pressure zones in the north Atlantic, and greater temperature contrasts
between the continental mass and the ocean.
36
Climate in Mesoamerica
The models project a regional increase of 1 to 2 ºC for 2011. Other
models predict that the temperature would be between 2 and 4 ºC
higher in 2080 (for scenarios B2 and A2, respectively). In general, an
overall increase in temperature is projected throughout the region,
with the extreme north of the region being affected by a greater
temperature increase than the extreme south. Toward 2080, for scenario A2, the temperature could rise by as much as 6.5 ºC in the far
north of Mesoamerica, in areas around Belize, Peten, and the border
between Guatemala and Mexico. In the most favorable scenario, the
temperature of that same area would rise by 4 ºC for 2080. The area
to the south of the Nicaraguan-Costa Rican border would experience a temperature increase of less than 2 ºC under both scenarios
(Figure 14). The rest of the region would experience gradual changes
between these geographic extremes.
Precipitation projections are more heterogeneous, both in spatial and
temporal terms. In general, the greater portion of the Mesoamerican
region, especially the Pacific coast, will experience a decrease in precipitation toward 2020. Under the favorable scenario, the exceptions are
the southwest coast of Guatemala and the far south of Panama, where
there would be a slight increase in precipitation—but only under the
favorable scenario. By contrast, under the unfavorable scenario, precipitation in the northeast coast of Honduras, all of Nicaragua, most
of Costa Rica and the central and northern portion of Panama would
decline by at least 20% (Figure 14, Table 4). The rest of the region
would also experience decreased precipitation under this last scenario,
although not as severe as the other areas mentioned. Other models
(Rausher et al. 2008) predict greater reductions in precipitation in
southern Guatemala, El Salvador, Honduras and western Nicaragua.
With regard to the spatial distribution of precipitation in the future,
there are differences between the recent models. For example, simulations done by SICA et al. (2006) and the results of PRECIS6, show
6 http://precis.insmet.cu/eng/Precis-Caribbean.htm and http://precis.insmet.cu/
eng/datos.html. Last visit 10/23/2010.
37
ABC of Climate Change in Mesoamerica
a
b
c
d
Figure 14. Changes in temperature and precipitation for Mesoamerica.
Anomalies in average annual temperatures (ºC) to 2080 for (a) the B2
scenario and (b) the A2 scenario, and anomalies in average annual
precipitation (%) to 2020 for (c) the B2 scenario and (d) the A2 scenario. The
colored vertical bars show the magnitude of change in ºC (a and b) and % (c
and d). Adapted from Anderson et al. (2008).
different precipitation trends for the northern and southern parts of
the region. In these simulations, Costa Rica appears as a transition
region. To the south of 7º latitude, an increase of approximately 2%
in precipitation is estimated, while to the north of that latitude a 12%
decrease in precipitation is estimated up to 2100. The latter models
38
Climate in Mesoamerica
coincide with those described by Anderson et al. (2008) with regard
to temperature. In addition, all the models analyzed coincide in predicting decreased precipitation during the rainy season.
Table 4.
Changes in temperature (ºC) and precipitation (%) for
Central America, for three time horizons. Ranges come from
seven global circulation models and the four families of IPCC
scenarios.
Variable
Season
Temperature (ºC)
Precipitation (%)
Year
2020
2050
2080
Dry
+0.4 to +1.1
+1.0 to +3.0
+1.0 to +5.0
Rainy
+0.5 to +1.7
+1.0 to +4.0
+1.3 to +6.6
Dry
-7 to +7
-12 to +5
-20 to +8
Rainy
-10 to +4
-15 to +3
-30 to +5
Source: Magrin et al. (2007).
39
Effects of climate change on Mesoamerica
3
Effects of climate change on Mesoamerica
According to the IPCC, the societies and natural systems of the
Mesoamerican region are highly vulnerable to extreme climate
events. This is due to a combination of geographic reasons (confluence of several ocean currents and effects of periodic climatic
oscillations such as El Niño/La Niña), and economic and social factors (low levels of social development, inequality in the distribution
of wealth, low capacity for adaptation).
The poorest communities are generally the most vulnerable; the
most affected are the most exposed. Around 54% of the population
living in poverty has a higher probability of suffering the adverse
effects of climate change7. Part of this vulnerability is due to the presence of populations in areas affected by hurricanes, unstable lands,
or in settlements on land prone to flooding. The region’s vulnerability to climate events is also exacerbated by the interactions between
demographic pressure, lack of planning for urban growth, poverty
and rural migration, limited investment in infrastructure and services, overexploitation of natural resources, pollution and problems
with inter-sectoral coordination.
Moreover, if a certain percentage of the region’s population lives in
extreme poverty, with their livelihoods based on natural resources
that are threatened by climate change, this part of the population is
more susceptible to suffering the adverse effects of climate change
and of becoming even poorer. In fact, climate change is already
7 http://www.alamys.org/default.asp?id=283&posicion1=4322. Last visit
10/23/2010.
41
ABC of Climate Change in Mesoamerica
compromising efforts to meet the commitments of the Millennium
Development Goals (see Manzanares et al. 2008).
The IPCC points out that changes in climate seasonality or annual
events have the potential to severely affect different sectors: water
resources and their management, terrestrial ecosystems, agriculture,
fibers and forest products, coastal systems, coral reefs and wetlands,
industries, health and society in general (Table 5). Many of these
sectors are closely linked together and climate change would produce simultaneous and synergistic effects among them. Furthermore,
the influence of human land and water use patterns are factors that
could place certain ecosystems at greater risk, or could improve the
survival of others.
In Mesoamerica, it is believed that most of the direct and indirect
effects of climate change will revolve around water availability.
Water scarcity has numerous repercussions: on biodiversity, on countries’ capacity to generate hydroelectric power, on the availability
of potable water, on the population’s health levels, on agricultural
production, etc. The sectors most affected by climate change are biodiversity, agriculture and human health.
The following section contains a general description of the potential
effects of climate change on different sectors in the region, offering local examples when possible. The main effects by country are
detailed in Annex 1. Given the scarcity of scientific and socioeconomic studies on observed and expected changes to natural and
human systems in Mesoamerican countries, some of the effects mentioned are generalized from effects expected in other regions. Due to
the diversity of sectors and processes involved, this is not an exhaustive review of all the possible effects of climate change.
42
Effects of climate change on Mesoamerica
Table 5.
Expected climate change and its possible effects
Expected changes
Projected effects
▲Mortality
and serious diseases in elderly
people and in the rural population
▲Thermal stress in cattle and in wild plants and
animals
▲Risk of damage to crops
▲Demand for electric refrigeration
▼Reliability in energy supply
Higher maximum
temperatures
More hot days
More heat waves
▲Distribution
and activity of pest and disease
vectors
▼Human morbidity and birth rates related to
the cold
▼Risk of damage to crops
▼Demand for caloric energy
Higher minimum
temperatures
Fewer cool days
Fewer frosts
▲Damage caused by floods and landslides
▲Soil erosion
▲Recharge of aquifers on some floodplains
▲Pressure on relief systems in the event of
More intense
precipitation
disasters
Greater risk of drought
Increased intensity of
hurricanes
Increase in average
and maximum
precipitation events
increase
▼:
▲Risk to human life
▲Coastal erosion
▲Risk of infectious disease epidemics
▲Damage to coastal infrastructure
▲Damage to coastal ecosystems (mangroves
and reefs)
Intensification of
droughts and flooding
associated with El Niño
▲:
▲Damage to buildings due to soil contraction
▲Risk of forest fires
▼Quality and quantity of water resources
▼Crop yields
▼Hydroelectric
energy generation potential (in
drought zones)
▼Agricultural and pasture productivity
reduction
Source: Adapted from SERMANAT & UNEP (2006), using IPCC data.
43
ABC of Climate Change in Mesoamerica
Water resources
Climate change has not only affected normal precipitation patterns,
but has also affected the periodicity, intensity and duration of various
climatic phenomena. Both an excess and a lack of water affect the
quantity and quality of water available for natural ecosystems and
human consumption. Greater precipitation produces an increase in
water flows and sediment runoff, creating problems with the quality
of potable water and the functioning of coastal-marine ecosystems. It
also increases the risk of flooding, with consequent effects on human
infrastructure, agriculture, livestock production, and health.
By contrast, a decrease in precipitation reduces the quantity of water
available in a watershed, a process that is exacerbated by the negative interaction with higher temperatures. In general, vulnerability
to water scarcity is greater in regions that are typically drier and
warmer. These vulnerabilities will also increase due to the negative
interaction between increased demand for water for domestic use
and irrigation (due to population growth), and the more arid conditions that are expected in many watersheds. The problem of water
scarcity will be further complicated in cases where land settlement
patters do not coincide with the distribution of this resource.
According to the IPCC, accelerated urban growth, increased poverty
and lower investment in water supply systems will contribute, among
other things, to water shortages in many cities, a high percentage of
the population with no access to sanitation services, a lack of water
treatment plants, the absence of urban drainage systems and high
levels of groundwater pollution. In the Central Valley of Costa Rica,
for example, an imbalance in the potable water supply is expected by
2022, due to a combination of climate change and an extra 1.1 million
people. In Mexico, per capita water availability will fall sharply from
11,500 m3/inhabitant/year in 1955 to 3,500 m3/inhabitant/year in 2025,
due to economic development and demographic growth.
44
Effects of climate change on Mesoamerica
Serious problems are also expected with the water supply for
human use on the plains, the Motagua Valley and the Pacific coast
of Guatemala; in El Salvador; in the Central Valley and Pacific coast
of Costa Rica; in the intermountain regions of northern, central and
western Honduras; and in the Azuero Peninsula in Panama. The
reduction in water availability will also affect capacity for hydroelectric energy generation in Belize, Honduras, Costa Rica and Panama.
In severe drought conditions, unsound agricultural practices (deforestation, soil erosion, and excessive pesticide use) will also degrade
the quality and quantity of surface and ground water. This would
occur in areas that are currently degraded such as León, the Sebaco
Valley, Matagalpa and Jinotega in Nicaragua; the metropolitan and
rural areas of Costa Rica; and other areas in Central America.
Biodiversity
According to the IPCC, it is very unlikely that all the changes observed
in many natural systems are solely due to their natural variability.
Instead, it is likely that global warming due to human activity over
the last 30 years has had a discernible influence on various natural
systems. However, it is still not possible to unequivocally attribute all
the responses observed in natural systems to anthropogenic global
warming. For example, the natural variability of temperature is
greater on smaller scales, which makes assigning a specific response
to global temperature patterns difficult. Moreover, on a small scale,
non-climatic factors such as changes in land use or the presence of
invasive species also influence the functioning of ecosystems.
Mesoamerica possesses approximately 9% of the world’s biological diversity. The importance of this wealth is undeniable, given
that it plays a major role in supplying goods and services that are
essential for human survival: food, fibers, fuels and energy, pastures, medicines, water and air quality, flood control, pollination, soil
45
ABC of Climate Change in Mesoamerica
formation, nutrient cycle regulation, and cultural, spiritual, aesthetic
and recreational values, among others. In general terms, climate
change—accentuated by forest fragmentation and deforestation—
is expected to affect all aspects of biodiversity. The most important
effects will include an increased rate of species extinction and the
displacement of habitats to higher latitudes and elevations.
In Mesoamerica, changes in the seasonality and intensity of precipitation (more than annual changes in temperature) will lead to the
replacement of rainy and wet climate zones with dry and very dry
zones. Montane and dry forests will be most vulnerable to this process. For example, in central and southern Mexico tropical forests
are expected to be replaced by savannahs, and semi-arid vegetation
by arid vegetation in most of central and northern Mexico. Similarly,
in Nicaragua and Costa Rica there is a very marked trend toward
an increase in very dry zones, to the detriment of wet zones (Figure
15). The complete displacement, or possible replacement, of certain
types of ecosystems would cause serious impacts to the diversity of
plants and animals, many of them already endangered (Table 6), as
well as to the environmental services currently provided by forests.
Not even protected areas, with their high diversity and vulnerability,
would be totally immune to these changes.
Species with high adaptive capacity and rapid dispersal (birds, mammals, some insects) could move to new areas with suitable climates.
However, in the case of montane forests, for example, the possibility of species relocating to more favorable conditions is practically
non-existent because the peaks of the mountain ranges constitute
the maximum physical limit where the species could migrate to and
subsist. Even in lowland forests, the longevity of some tree species
and the constraints imposed by their dispersal systems and growth
habits would make it difficult for them to migrate to new areas with
climates suitable for their development.
46
Effects of climate change on Mesoamerica
Biological productivity is another important aspect of biodiversity
that is affected by climate change. These changes can affect goods
and services essential for humanity (production of foods, fibers, timber, etc.), as well as the way in which the carbon cycle functions on
Figure 15. A) Map of existing life zones in Costa Rica and B) Map of potential life
zones in Costa Rica by 2020 under a B2 scenario. Taken from Jiménez (2009).
47
ABC of Climate Change in Mesoamerica
land and in the oceans, and the number and types of organisms in
the ecosystems. Changes in or losses of certain organisms from an
ecosystem could also cause losses in net productivity. In the case of
forests, this could translate into a reduction in the timber supply (at
a time when demand continues to rise), which would also lead to
greater pressure on remnant forests.
Climate change severity index
The climate change severity index (CCSI) measures the magnitude
of climate change in a particular place, relative to the natural climate
variations historically experienced in that place. Data for calculating
Table 6.
Number of known mammal, bird and higher plant species
that are endangered in Mesoamerica.
Taxonomic group
Threatened
species
Known
species
Threatened
species
Known
species
Threatened
species
Higher plants
Belize
125
4
161
2
2894
28
Costa Rica
205
14
279
13
12119
109
El Salvador
135
2
141
0
2911
23
Guatemala
250
6
221
6
8681
77
Honduras
173
10
232
5
5680
108
Mexico
491
70
440
39
26071
--
Nicaragua
200
6
215
5
7590
39
Panama
218
20
302
16
9915
193
Country
Source: UNDP et al. (2003).
48
Birds
Known
species
Mammals
Effects of climate change on Mesoamerica
the CCSI came from Worldclim. Although the CCSI has been calculated for three different climate models (Anderson et al., 2008), the
results given here only describe outcomes for the A2 and B2 scenarios calculated with the HADCM3 model only. It is important to bear
in mind that similar calculations using other models can produce different results.
Under the B2 scenario for 2050, the CCSI suggests few significant
impacts; these are concentrated mainly toward the east coast of
Nicaragua and the southern end of Panama. By contrast, under the
A2 scenario for 2050, practically all of Mesoamerica would experience significant changes in its climate conditions (see red area
in Figure 16). Climate change severity would be greatest on the
Caribbean coast of Costa Rica and Panama (black area in Figure 16).
The differences between the two scenarios underscore the importance of implementing mitigation efforts, in order to reduce the
possible impacts of climate change.
All the ecosystems of Mesoamerica will be affected to a greater or
lesser degree by climate change. In the A2 scenario, at least 25% of
the area with broadleaf forests, coniferous forests, mangroves, mixed
forests, scrub forests, wetlands and agriculture will experience imminent significant changes. The CCSI indicates that approximately 15%
of the area covered by broadleaf forests and agriculture and between
5 and 10% of the area with savannahs and mangroves would experience climate changes outside the range of their natural historic
variability.
Terrestrial ecosystems
As in the case of the Amazon, Central America’s forests are at high
risk of having their area reduced due to increases in temperature.
Forests will likely be replaced by savannahs, which are ecosystems
that are more resistant to the multiple influences caused by increased
temperatures, droughts and fires. Although fire could become a more
common modifying element of Central American ecosystems, it is
49
ABC of Climate Change in Mesoamerica
B2 Scenario
Climate Change Severity Index
Low severity
Approaching significant changes
Approximate areas of land
in each category (1000 km2)
Significant changes vary during year
Pushing comfort zone limits
Outside comfort zone
Far outside comfort zone
A2 Scenario
Climate Change Severity Index
Low severity
Approaching significant changes
Approximate areas of land
in each category (1000 km2)
Significant changes vary during year
Pushing comfort zone limits
Outside comfort zone
Far outside comfort zone
Data Derived from:Wordclim Climate Grids: Current and Future
Conditions (HADCM3 A2 & B2) 2008.
Figure 16. Climate change severity index for Mesoamerica in 2050, for the B2
scenario (a) and the A2 scenario (b). The bar graphs in the boxes show the
land area in each category of severity. Adapted from Anderson et al. (2008).
50
Effects of climate change on Mesoamerica
not expected to be a determinant factor in the disappearance of
forests. The future incidence of fires and their influence on the ecosystems is an aspect that has not been well studied in Mesoamerica.
In moist lowland forests, there is documentation showing that
productivity falls and mortality increases during years when high
temperatures and low precipitation prevail. On the other hand,
research in Brazil indicates that the dynamism (higher growth,
higher mortality, increase in species adapted to perturbed areas) of
moist forests appears to be increasing, possibly due to the increase
in atmospheric CO2 and climate changes. Therefore, Mesoamerican
forests can be expected to respond similarly.
The height of the cloud layer during the dry season has been rising
at a rate of 2 m per year, due in part to deforestation. If this increase
continues and the temperature also increases 1 or 2 ºC in the next 50
years, the montane cloud forests will be threatened. In locations at
lower elevations or on isolated peaks, some species of plants and animals could go extinct because the range of elevation would not allow
them to adapt naturally to the temperature increases. This could
have severe negative impacts on species diversity and composition.
For example, in Monteverde, Costa Rica, fewer cloudy days have
already been strongly associated with a 40% reduction in amphibian
populations. It is also known that lower relative humidity causes the
death of epiphytes and other plants.
Populations of amphibians (mainly frogs and toads) are being affected
in the cloud forests after years of low precipitation. Moreover, links
have been found between higher temperatures and frog extinctions
caused by pathogens. In Costa Rica, the extinction of the golden toad
(Bufo periglenes) is attributed in part to an increase in the temperature of its habitat, which fosters the proliferation of a cutaneous
fungus. Temperature changes would affect the migration patterns
of certain species and alter the phenology (biological events such
as flowering and fruiting of plants, reproductive seasons) of others.
51
ABC of Climate Change in Mesoamerica
For example, the ranges of elevation of some tropical forest birds of
Costa Rica have expanded as the temperature has risen.
Aquatic ecosystems
According to the IPCC, the impacts that will have the most serious
socioeconomic consequences are: population displacement, saltwater intrusion in low areas (with the associated degradation of
potable water sources), changes in storm regimes, increased erosion
and modification of coastal morphology, displacement of crop areas,
disruption of access to fishing areas, negative impacts on biodiversity
(including mangroves and wetlands), salinization and overexploitation of water resources (including groundwater, which would affect
the availability of potable water for coastal populations), and pollution and acidification in coastal and marine environments.
Freshwater systems
The IPCC considers freshwater systems to be very sensitive to climate change. There are few studies of how changes in temperature
could affect species in rivers and lakes. However, it is expected that
falling water levels in rivers and reservoirs alone would negatively
affect the species that develop there. Furthermore, studies conducted
in other latitudes indicate that rising water temperature would modify the thermal cycles of lakes and the solubility of oxygen and other
elements, thereby affecting the structure and functioning of these
ecosystems.
The effects of climate change on wetlands are still very uncertain
and are seldom included in global models of climate change effects.
However, in general terms, temperature increases, rising sea level,
changes in precipitation, and higher evapotranspiration, together
with changes in land use and overexploitation of water resources,
will degrade these goods and services. These changes could affect
aquatic birds that depend on wetland habitats and it is possible that
they will contribute to desertification.
52
Effects of climate change on Mesoamerica
Mangrove forests and coral reefs
Mangrove forests and reefs are highly interconnected habitats.
Reefs, like mangrove forests, stabilize and protect coastal landscapes,
contribute to the maintenance of coastal water quality and function
as the main habitat of numerous mammals, birds, reptiles and fish,
many of which are commercially important. The effects of climate
change would be added to those produced by the large amount of
sediments produced mainly by agricultural activities in the countries
of the Mesoamerican reef.
Mangrove forests are possibly the coastal ecosystems that would be
most affected by rising sea level, rising temperature, and the higher
frequency and increased intensity of hurricanes and storms, with their
associated impacts on fishing activity and the food industry based on
marine products. In the Mesoamerican reef area, the abundance of
some fish species can be up to 25 times higher near mangroves than
in areas where these have been destroyed8. Loss of mangrove forests
would greatly reduce this diversity. On the other hand, in countries
such as Belize, mangrove forests also act as buffer zones against the
direct effects of wave action, protecting nearly half the length of the
coastline and up to 75% of the coasts of the cays. The degradation
of these ecosystems would also increase the vulnerability of coastal
infrastructure.
Central America has the second largest barrier reef in the world,
extending for 1,000 km from the northeastern Yucatan Peninsula in
Mexico to the Bay Islands of Honduras. Rising sea temperature and
water acidity has caused the death of large areas of coral, and not just
in Mesoamerica. A 1 ºC rise in sea temperature causes episodes of
bleaching (often partially reversible) in corals, while a 3 ºC rise can
cause their death. Higher water temperature can also increase the
incidence of diseases that affect corals and seagrass beds, and influence the quantity and distribution of marine organisms. Moreover,
8 http://central-america.panda.org/about/countries/belize/?uNewsID=16870. Last
visit 17-05-09.
53
ABC of Climate Change in Mesoamerica
at an atmospheric CO2 concentration above 450 ppm (currently this
is 384 ppm and rising), coral diversity would be lost due to water
acidification.
A study based on data for 1977–2001 reveals that the coral cover of
the Caribbean reefs diminished by an average 17% in just one year
after the passage of a hurricane, without any evidence of recovery
for at least eight years after the impact. After hurricanes Emily and
Wilma in 2005, significant changes were seen in the physical structure
and species diversity of the Cozumel reefs. In addition to the structural and biological damage caused by extreme events, coral reef
degradation can have severe impacts on the economies of countries.
In Belize, tourism associated with activities in mangroves and reefs
contributed 150 to 196 million dollars (12 to 15% of GDP) in 2007.
It is also estimated that the presence of these ecosystems prevents
losses of 231 to 347 million dollars by helping mitigate the erosive
and destructive effects of the sea.
Despite the major impacts of climate change on coastal-marine
resources, other factors—such as resource extraction, residential,
tourism and commercial development, water pollution by industrial
discharges and urban wastes, and agricultural activities—currently
exert greater pressure on coastal ecosystem biodiversity.
Coastal zones
Significant impacts from climate change and rising sea level are
expected for 2050–2080 in all coastal areas of Latin America. With
most of the region’s population, economic activities and infrastructure located very near sea level, it is very likely that the coastal zones
(beaches, estuaries, coastal lagoons, river deltas) will suffer flooding
and erosion, with serious impacts on populations, resources and economic activities.
The impact on coastal tourism will be considerable in Central
America because this sector contributes significantly to GDP
54
Effects of climate change on Mesoamerica
through the creation of jobs, and the promotion of public services
and state taxes. Furthermore, this sector would also be affected by
storms and rising sea level.
The coasts, coastal cities and ports of Belize, Costa Rica, El Salvador,
Mexico and Panama are among the places most vulnerable to climate
variability, hydro-meteorological events, and tropical and subtropical cyclones. Between 1909 and 1984, sea level rose 1.3 mm per year
in Panama (approximately 9.8 cm in 75 years), thereby increasing
its vulnerability to extreme tides. In southern Mexico, the areas of
major marine influence would reach up to 50 km inland, in the case
of rivers and wetlands.
Fisheries
The effects of climate change on freshwater fisheries will depend on
the species and local climate modifications. There are information
gaps regarding many aspects of marine and aquatic environments.
For example, there are no detailed regional inventories documenting
the distribution of aquatic and marine species. There is also a lack of
information about marine pH, salinity and temperature at various
depths.
Despite these limitations, it is considered very likely that climate
change will interact with human influences on the oceans to negatively affect oceanic fisheries. For example, fishery production
is expected to suffer if wetlands and other coastal habitats that
serve as nurseries are lost as a consequence of rising sea level and
the increased discharge of sediments and agricultural wastes. In
Nicaragua, a reduction in the production of shrimp, conch and oysters is expected. Even so, IPCC models assume that ocean fisheries
will remain stable or grow significantly- if and when management
deficiencies are corrected. This last assumption is critical, because
fishing has been confronting serious problems of sustainability for
many years now.
55
ABC of Climate Change in Mesoamerica
Agriculture and cattle ranching
Generalities of the sector
The agricultural sector is considered to be doubly exposed because,
on the one hand, it is vulnerable to strong socioeconomic changes
associated with the process of economic globalization and, on the
other, it is sensitive to climate variations. In addition to purely climatic effects, food production and food security are closely related
to land degradation and erosion patterns. A paradigm shift will be
required for agriculture to confront changes in productive potential
and the pressure of increased population.
Climate change impacts agriculture and the rural milieu in many
ways. The main direct effects of climate change on agriculture
would be changes in the duration and seasonality of crop cycles,
physiological alterations from temperatures higher than those to
which crops are adapted (which would lead to crop losses), water
shortages (which would reduce soil moisture, as well as changes in
infiltration and runoff) and increased erosion (due to soil desiccation and greater surface runoff). Increased CO2 concentrations have
the potential to raise the productivity of some crops but this effect
is limited. Indirectly, climate change would affect the incidence of
pests and diseases, the cycling and availability of nutrients in the soil,
increased propensity for fires, etc.
All these factors have the potential to reduce agricultural production, de-capitalize the sector, increase unemployment, encourage
migration to urban areas and complicate access to credit, among
other problems. Agriculture has traditionally been one of the main
sources of employment and a leading generator of revenues for the
countries of the region. Although the agriculture sector’s contribution to GDP has declined since 1990, it recently represented nearly
20% of GDP in Belize, Guatemala and Nicaragua, from 10% to
20% in Honduras and El Salvador, and less than 10% in Costa Rica,
Mexico and Panama (UNDP, 2003). The agriculture sector is where
56
Effects of climate change on Mesoamerica
most of the losses due to extreme climate events have been concentrated. For example, 49% of the losses caused by Hurricane Mitch
were concentrated in the agriculture sector, while losses due to
droughts could reach 60%. In Mexico, droughts represent 80% of all
the agricultural catastrophes that occurred between 1995 and 2003.
In addition, agriculture is linked to maintaining public health through
its role as the basic source of foods necessary for nutrition. To summarize, the effects of climate change on agriculture would affect
human wellbeing and would negatively impact the sector’s potential
contribution to national GDP.
Changes in production
During El Niño/La Niña events, studies have documented reductions in the growth of mangos and other crops, increases in the
incidence of pests and pathogens in corn, potatoes, wheat and beans,
and reductions in milk production due to rising temperatures. Crops
such as bananas, traditionally cultivated in lowlands, have historically
borne the brunt of extreme precipitation and flooding events. Based
on climate predictions, it is likely that areas planted with banana will
experience even greater impacts. In Mexico, any shift toward warmer
and drier conditions could trigger a nutritional and economic disaster because agriculture is already under pressure from scant and
variable precipitation.
Basic grains have also been subject to fluctuations in production due
to climate changes. In South America significant increases have been
reported in the production of soybeans (38%), corn (18%), wheat
(13%), sunflower (12%) and grasslands (7%). However, in Central
America, changes in agricultural productivity are more variable. In
Costa Rica it is estimated that a 2 ºC rise would benefit coffee production, but the same temperature rise, combined with a 15% reduction
in precipitation would reduce the country’s potato and rice production. In Guatemala, with a 1.5 ºC rise in temperature and a 5%
reduction in precipitation, bean production would vary from -28% to
57
ABC of Climate Change in Mesoamerica
+3%, while for corn it would vary from -11% to +8%, and for rice it
would be reduced by 16%. In Mexico, the proportion of the national
territory suitable for seasonal corn cultivation would be reduced from
11% to only 4% (Flores et al. 1996), as this particular crop is most
vulnerable to climate change. In Honduras, a reduction of 21% in
corn production for 2070 is estimated. In Panama, a similar reduction
in rice production is estimated for 2100. However, in 2010 and 2050
increases of 9% and reductions of 34% are estimated, respectively.
In Nicaragua, a drastic reduction in basic grains is expected, which
would affect food security. Nevertheless, there are incipient experiences aimed at replacing corn with sorghum in the northern part of
the country. The departments of Chinandega, León, Managua and
Masaya in Nicaragua will suffer severe reductions in crop yields in the
next 50 years. Variations in pest populations and diseases due to climate change will also play a role in reducing agricultural production.
Variations in the production of basic grains could also depend in part
on the response of these crops to higher concentrations of CO2 in the
atmosphere (an effect known as “CO2 fertilization ”). For example,
it is estimated that if the effects of CO2 are not taken into account,
grain production would be reduced by up to 30% in 2080. On the
other hand, if the effect of CO2 is taken into account in the forecasts, grain production would be reduced by 30% in Mexico, but
would increase by 5% in Argentina. Production would also increase
for other crops such as corn, sorghum and sugarcane. Despite these
increases, experiments on the addition of CO2 have shown that the
fertilization effect is short-lived and that eventually other elements
critical for plant growth (nutrients, water, organic matter) will limit
increased production. For example, a temperature rise of around 2
ºC, combined with lower water availability, would reduce production
in tropical countries by up to 60%.
In the case of cattle ranching in Costa Rica, it was found that both
prolonged and seasonal dry periods can affect the health of cattle,
either due to emerging diseases and pests or the lack of pasture.
58
Effects of climate change on Mesoamerica
Moreover, higher temperatures lead to lower yields due to the thermal stress the animals suffer.
Human health
Generally, the interaction of biotic, abiotic and socioeconomic factors (occupational health, disasters, pollution) has an influence on
the existence, exposure and susceptibility of an infectious agent that
causes a disease in a given host. Demographic and social factors such
as urban development and human migration due to droughts, growing poverty in urban areas and environmental degradation could also
promote new forms of vector reproduction and disease dispersal.
Overall, higher incidences of vector-transmitted diseases (dengue and its hemorrhagic variety, malaria, leishmaniasis and yellow
fever) are expected. In these diseases, the influence of climate
changes is rather indirect, since it is the vectors that respond to the
fluctuations in temperature, precipitation, solar radiation and relative humidity. For example, it is known that dengue is commonly
transmitted in areas with temperatures above 20 ºC. In Mexico, it
has been shown that a 3 or 4 ºC rise in average temperature can
double the dengue transmission rate. Furthermore, in coastal areas
of that country, the transmission cycles of this disease are correlated with sea surface temperature, minimum air temperature and
precipitation. Some models predict a substantial increase in the
number of people at risk of contracting dengue in Honduras and
Nicaragua, as the geographic limits of transmission are displaced,
along with rising temperatures.
Malaria would also expand its geographic distribution. This disease
presents a serious health risk, particularly in El Salvador, where the
risk of transmission is 100%. An increase in the incidence of malaria
is also expected in Nicaragua, with seasonal variations from 2010 on.
A 1 ºC rise in temperature would increase the occurrence of malaria
59
ABC of Climate Change in Mesoamerica
by 1% in Mexico. The risk of contracting this disease would thus be
much greater for the entire region in 2030. Increases in malaria -and
in the population at risk of contracting this disease- could impact
health service costs, including payments for treatments and social
security.
Leishmaniasis is a disease associated with prolonged droughts,
while leptospirosis is related to floods and problems with stagnant
water. Outbreaks of hantavirus have been reported in several Latin
America countries, including Panama, after prolonged droughts.
The incidence of non-vector transmitted infectious diseases (cholera, typhoid fever, salmonellosis, shigellosis, etc.) could also increase,
mainly due to changes in the distribution and quality of surface water.
Gastrointestinal and respiratory diseases will also be more common.
Although gastrointestinal diseases may respond to the incidence of
floods or droughts, the absence of basic hygiene infrastructure, overcrowding of the population and water scarcity could be determinant
factors in the occurrence of these diseases. In Costa Rica, a rise in the
incidence of asthma is expected by 2015, partly due to an increase in
temperature and humidity fluctuations. Subsequently, asthma cases
could diminish as air quality improves in the Greater Metropolitan
Area. The most direct effect of climate change on human health
would be sunstroke, which mostly affects the population over 65
years of age and people with pre-existing disease conditions. In
Mexico it is estimated that mortality would increase by at least 1% if
temperature rose only 1 ºC.
Disasters
Central America is one of the regions with the highest probability
of disasters, due to its geographic position, its high levels of vulnerability and the increase in natural and human threats. Disasters in
the Central American region have increased to an annual rate of 5%
60
Effects of climate change on Mesoamerica
over the last 30 years. However, climate change alone is not responsible for all disasters that occur in the region. Rather, these interact
with social and infrastructure factors, such as9 the following:
•The concentration in high risk zones of populations with low
economic capacity for absorbing the impact of disasters and
recovering from their effects;
•The establishment of human settlements in areas prone to
hazards, such as river banks and wetlands, with fragile and insecure living conditions and insufficient social infrastructure and
services;
•Impoverished rural areas suffer a progressive increase in threat
levels due to environmental degradation processes; and
•Public and private institutions and national and local governments have weak capacity for risk reduction and management.
There are no detailed studies quantifying the potential future costs
associated with climate change in the region. However, based on an
analysis of past events, the costs would be significant. It is estimated
that between 1970 and 2002 average economic losses caused by disasters in the region exceeded 318 million dollars per year. In Mexico,
the 1997–1998 El Niño alone was responsible for approximately 204
million dollars in crop losses.
Although the number of deaths due to natural disasters has declined
since 1972, the total population affected has increased considerably.
The extensive damage associated with Hurricane Mitch (in 1998)
was calculated at approximately 8.5 billion dollars, which set back
the region’s economic development for a decade or more. Damage
due to natural disasters in 2005 reached 6,448 billion dollars in
Mesoamerica and the Caribbean. Hurricane Stan produced losses
of 998 million dollars in Guatemala alone. This is equivalent to just
over 3.4% of GDP for 2004, or 39% of gross capital formation in that
country, which had a significant impact on the rate of GDP growth.
In comparison, the damage caused by Hurricane Ivan in the Cayman
9 http://www.sica.int/cepredenac/contexto_reg.aspx. Last visit 10/23/2010.
61
ABC of Climate Change in Mesoamerica
Islands, Grenada and Jamaica represented 183%, 212% and 8% of
GDP, respectively, for those countries in 2004. Meanwhile, Nicaragua
is the second country in the world that is most affected by tropical
storms. About 25% of its population is at risk from storms and hurricanes, and 45% is vulnerable to droughts. In 2007, Hurricane Felix
caused losses of more than 300 million dollars in Nicaragua.
Since the effects of these disasters are cumulative and the resilience
of systems is reduced following repeated events, the occurrence of
more than one natural disaster per year could impact the countries
even more severely.
Other sectors
Climate change threatens to paralyze and reverse advances in
human development such as the reduction of extreme poverty, the
strengthening of public health, improvements in agricultural production, nutrition and education etc.
One seldom considered factor, but one of great importance for the
region, is the stability of the indigenous populations. These communities depend directly on the various resources provided by ecosystems
to satisfy many of their basic needs. Due to their geographic, demographic and socioeconomic characteristics, these human groups have
low adaptive capacity and high susceptibility to climate changes.
62
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71
•2–4 ºC rise by
2050
•5–20%
reduction in
precipitation
•Northern
Mexico with
greater
changes
•Increase in
severe storms
and more
extreme and
prolonged
periods of
drought
•52–58%
of country
affected by
climate change
Climate
variables
•Moderate to
strong pressure
(10–40%) on
southern Mexico
by 2030
•States more
vulnerable to
drought in the
south: Oaxaca,
Quintana Roo,
Campeche,
Chiapas, and the
eastern Yucatan
Peninsula
Water resources
Sector
Health and other
Agriculture
human aspects
Mexico
•>40% of nation will •Increased risk of
deaths due to heat
suffer changes in
waves
suitability for corn
•Increased dengue
production
and malaria
•Area suitable for
seasonal corn
will disappear
in southern and
southeastern
regions
Forest
resources
•50% of
•Reduced
forest area
environmental
will undergo
services and
changes
ecosystem
•Cold, moist
stability
temperate
•Endemic species
show reduction in forests in the
mountainous
their ranges
zones of
Oaxaca and
Chiapas will
be the most
affected
Biodiversity
Effects of climate change on different sectors of society in Mesoamerican countries
Annex 1
•Gulf of Mexico and
the Caribbean Sea
susceptible to rising
sea level
•Coastal strand
unsuitable for
agriculture will be
displaced further
inland
•Coastal zones
affected: Yucatán
(Los Petenes) and
Quintana Roo (Sian
Ka'an Bay and
Chetumal)
Coastal zones
Annex
73
74
Water resources
Agriculture
•Reductions of up to
•In a pessimistic
•Increased
66% in harvests of
scenario:
temperature
some basic grains
10– 50%
•Reduction of
•Crop losses of
reduction in
precipitation
vegetables, fruits
runoff and
year-round
and cereals in
diminished
and more
watersheds and of
water sources
pronounced dry
coffee, sugarcane
for human
season
and and cattle near
and animal
•Maintenance
the coast
or expansion of
Consumption and
•Responses depend
for irrigation
semi-arid areas
on region and crop:
•In an optimistic
Corn: -34 to +15%,
scenario: runoff
Bean: -66 to +3%,
could increase
Rice: -27 to -16%
15%
Climate
variables
Sector
Health and other
Forest
Biodiversity
Coastal zones
human aspects
resources
Guatemala
•Sea level rise of
•Modifications
•Changes in seasonal •Sub-tropical
6 to 34 cm by
to forest cover,
zones reduced by
Patterns of acute
2030, depending
diversity,
respiratory infections, 32–27%, giving
on scenario and
development
way to tropical
acute diarrhea and
and productivity assuming a 1.5 ºC
zones (Petén,
malaria
temperature rise
northern Quiché, •Coniferous
•Increase in diarrhea,
forest area
Alta Verapaz,
parasite and skin
reduced
Izabal, southern
diseases
due to an an
and southeastern
expansion of
areas)
the dry zone
•Moist and
temperate zones •Coniferous and
mixed forests
reduced by 25%
(3.7% of nation)
in upper areas of
will be affected
mountain ranges
ABC of Climate Change in Mesoamerica
•Reduction in
the production
and quality of
Sugarcane, banana
and corn
•Floods and higher
salinity on crop
lands of the coast
•Greater soil erosion
•Increased
agricultural pests
and diseases
•Higher salinity in
rivers, aquifers
and groundwater, affecting
potable water
availability
•With a 1 m rise
in sea level, all
the cays will lose
their potable
water sources
•Corn production
reduced by 22%
Agriculture
Water resources
•1.8–3.7 ºC
•1276 km2 of
lands lost to
temperature
floods
rise by 2100
•Reduction of
37–8% by 2100
•Temperature
increase
between
0.8–3 ºC
•Changes in
precipitation
from -42 to
+18%
Climate
variables
Honduras
Sector
Health and other
human aspects
Belize
•Flooding will affect
communication,
infrastructure and
cities
•45% of the
population of Belize
forced to migrate
inland
•Diminished marine
tourism
•Mortality of
corals due to
higher ocean
temperature
and acidity and
physical storm
damage
•Loss of habitat
for commercial
fish species
•Reduction in
fishery potential
Biodiversity
Coastal zones
•Mangroves, wetlands
and reefs affected by
rising sea level
•Loss of tourist
attractions
•Effects of rising sea
•Changes
level: flooding of
in species,
wetlands, lowlands
degradation
and coasts, more
of structure,
coastal erosion, loss
effects of pests
of beaches
and diseases,
•Severe impacts on
increased
coastal infrastructure
forest fires
and structures close
•Damage to
to sea level
mangroves
•Damage to
infrastructure and
reduction of water
quality in aquaculture
areas
•Flooding of cays
Forest
resources
Annex
75
76
Water resources
•Increased
•Temperature
flooding
increase of
•Saltwater
2.5–3.7 ºC in
intrusion would
2100
affect potable
•Variation in
water sources
precipitation of
-37 to +11% in
2100
•Intensification
of dry season
and droughts
Climate
variables
•Reduction in agricultural production
(basic grains)
•Losses due to
drought or flooding
in the agricultural
sector, up to
$45million in 2100
•Losses of 80% in
cattle production
•Losses of
Infrastructure for
production
Agriculture
Sector
Health and other
Biodiversity
human aspects
El Salvador
•Migration of
•Increased poverty
species to new
and worsening
habitats due to
health, nutrition and
rising sea level
education
•Reduction in sources •Reduction or
extinction of
of jobs in all sectors
marine and
•Degradation of
continental plant
tourism potential
and animal
species
•Loss of
mangroves
Forest
resources
•Loss of 10–28% of
land area with sea
level rise of
0.13–1.1 m
•Migration of fishery
species to deeper
waters
•Reductions of
16–23% in artisanal
shrimp fishery volume
Coastal zones
ABC of Climate Change in Mesoamerica
•Precipitation
decline 8–37%
•0.8–3.7 ºC
temperature
rise
Climate
variables
•Atlantic zone the
least affected by
water resource
reduction
•Reductions
of 34–60% in
hydroelectric
energy
generation in
2100
•Reduction in
aquifer capacity
•Runoff
diminished
37–57% in 2100
Water resources
Agriculture
Sector
Health and other
human aspects
Nicaragua
•Malaria increased
38–150%
Forest
resources
•Life zones would •Modifications
change in 72% of
in forest cover,
country
diversity,
growth and
productivity
Biodiversity
Coastal zones
Annex
77
78
Water resources
•Problems of
•Reduction of
precipitation by
erosion and
sedimentation,
46 to 63%
•Temperature
with
repercussions
rise of
3.2–3.5 ºC
for use of the
resource and
hydroelectric
energy
generation
•Variations
(positive and
negative,
depending on
the scenario) in
runoff
Climate
variables
•Reductions in
production of rice,
beans and potatoes
•Coffee increases
production with a
2 ºC. temperature
rise, with a good
water supply
Agriculture
Sector
Health and other
human aspects
Costa Rica
Forest
resources
Coastal zones
•Migration of
•Breaches of the
•Reduction
species, loss of
coastline and
of montane,
diversity
expansion of areas
premontane, wet
prone to tidal flooding
and rainforest life
•With a 0.3 m sea
zones
level rise, 60% of
•Wet tropical and
Puntarenas would be
dry tropical life
flooded (90% with a
zones would be
1m rise)
the most affected
•Plant and animal
species at the
lowest or tropical
belt would be the
most vulnerable
Biodiversity
ABC of Climate Change in Mesoamerica
Agriculture
•Reduction in rice
•Increased
yields
salinity in coastal
•Enhanced corn
aquifers
•Negative changes production to 2010,
with subsequent
in water quality
•Reduction of up
reductions to 2100
to 26% in river
flows
Water resources
Sector
Health and other
human aspects
Panama
•Increase in human
diseases
•Increased land
area of drier life
zones
•Loss of
ecosystems due
to agricultural
pressure
•Migrations and
loss of biological
diversity
Biodiversity
•Changes
in floristic
composition,
migration
of species,
disappearance
of others
Forest
resources
•Flooding and
displacement of
wetlands and coasts
•Coastline erosion
•Increased storm
flooding
Coastal zones
Source: SEMARNAT (1997), SERNA (1997), MARN-SV (2000), MINAE (2000), MARN-GU (2001), MARENA (2001), BELICE (2002),
SEMARNAT-INE (2007), CATHALAC et al. (2008), Santos y García (2008).
•Increase in
precipitation
Climate
variables
Annex
79
ABC of Climate Change in Mesoamerica
Annex 2
Treatment of scientific uncertainty by the IPCC
(Adapted from Solomon et al. 2007.)
“Uncertainty” in the scientific context is a measure of the range of
variability of a determined measurement or of the probability of
occurrence of a determined phenomenon. In other words, scientific
uncertainty is a measure of certainty that describes the limits of the
knowledge attained. This definition contrasts with the colloquial use
of the word, which refers to the lack of clear and certain knowledge
of something.
The IPCC distinguishes between confidence levels in scientific
knowledge and the probability of the occurrence of certain events.
The confidence level in the precision of a result is described using the
following terminology:
80
Confidence level
Precision of the statements
Very high
At least 9 out of 10
High
About 8 out of 10
Medium
About 5 out of 10
Low
About 2 out of 10
Very low
Less than 1 out of 10
Annex
At the same time, the probability of occurrence of an event is
expressed in IPCC reports using the following standard terminology:
Probability of occurrence
Likelihood of occurrence/outcome
Virtually certain
>99%
Very likely
>90%
Likely
>66%y
More likely than not
>50%
About as likely as not
33 to 66%
Unlikely
< 33%
Very unlikely
< 10%
Exceptionally unlikely
< 1%
81