United States
Environmental Protection
Agency
Office of Policy
(2111)
EPA 236-F-98-007p
September 1998
<>EPA Climate Change And New Mexico
The earth's climate is predicted to change because human
activities are altering the chemical composition of the atmosphere
through the buildup of greenhouse gases — primarily carbon
dioxide, methane, nitrous oxide, and chlorofluorocarbons. The
heat-trapping property of these greenhouse gases is undisputed.
Although there is uncertainty about exactly how and when the
earth's climate will respond to enhanced concentrations of
greenhouse gases, observations indicate that detectable changes
are underway. There most likely will be increases in temperature
and changes in precipitation, soil moisture, and sea level, which
could have adverse effects on many ecological systems, as well
as on human health and the economy.
The Climate System
Energy from the sun drives the earth's weather and climate.
Atmospheric greenhouse gases (water vapor, carbon dioxide,
and other gases) trap some of the energy from the sun, creating
a natural "greenhouse effect." Without this effect, temperatures
would be much lower than they are now, and life as known today
would not be possible. Instead, thanks to greenhouse gases, the
earth's average temperature is a more hospitable 60°F. However,
problems arise when the greenhouse effect is enhanced by
human-generated emissions of greenhouse gases.
Global warming would do more than add a few degrees to today's
average temperatures. Cold spells still would occur in winter, but
heat waves would be more common. Some places would be drier,
others wetter. Perhaps more important, more precipitation may
come in short, intense bursts (e.g., more than 2 inches of rain
in a day), which could lead to more flooding. Sea levels would
be higher than they would have been without global warming,
although the actual changes may vary from place to place
because coastal lands are themselves sinking or rising.
The Greenhouse Effect
Some solar radiation
is reflected by the
earth and the
atmosphere
Some of the infrared radiation passes
through the atmosphere, and some is
absorbed and re-emitted in all directions
by greenhouse gas molecules. The effect
of this is to warm the earth's surface and
the lower atmosphere.
Source: U.S. Department of State (1992)
Emissions Of Greenhouse Gases
Since the beginning of the industrial revolution, human activities
have been adding measurably to natural background levels of
greenhouse gases. The burning of fossil fuels — coal, oil, and
natural gas — for energy is the primary source of emissions.
Energy burned to run cars and trucks, heat homes and busi-
nesses, and power factories is responsible for about 80% of
global carbon dioxide emissions, about 25% of U. S. methane
emissions, and about 20% of global nitrous oxide emissions.
Increased agriculture and deforestation, landfills, and industrial
production and mining also contribute a significant share of
emissions. In 1994, the United States emitted about one-fifth of
total global greenhouse gases.
Concentrations Of Greenhouse Gases
Since the pre-industrial era, atmospheric concentrations of carbon
dioxide have increased nearly 30%, methane concentrations have
more than doubled, and nitrous oxide concentrations have risen
by about 15%. These increases have enhanced the heat-trapping
capability of the earth's atmosphere. Sulfate aerosols, a common
air pollutant, cool the atmosphere by reflecting incoming solar
radiation. However, sulfates are short-lived and vary regionally,
so they do not offset greenhouse gas warming.
Although many greenhouse gases already are present in the
atmosphere, oceans, and vegetation, their concentrations in
the future will depend in part on present and future emissions.
Estimating future emissions is difficult, because they will
depend on demographic, economic, technological, policy, and
institutional developments. Several emissions scenarios have
been developed based on differing projections of these under-
lying factors. For example, by 2100, in the absence of emissions
control policies, carbon dioxide concentrations are projected
to be 30-150% higher than today's levels.
Current Climatic Changes
Global mean surface temperatures have increased 0.6-1.2°F
between 1890 and 1996. The 9 warmestyears in this century all
have occurred in the last 14 years. Of these, 1995 was the warmest
year on record, suggesting the atmosphere has rebounded from
the temporary cooling caused by the eruption of Mt. Pinatubo in
the Philippines.
Several pieces of additional evidence consistent with warming,
such as a decrease in Northern Hemisphere snow cover, a
decrease in Arctic Sea ice, and continued melting of alpine
glaciers, have been corroborated. Globally, sea levels have risen
-------
Global Temperature Changes (1861-1996)
Year
Source: IPCC (1995), updated
4-10 inches over the past century, and precipitation over land has
increased slightly. The frequency of extreme rainfall events also
has increased throughout much of the United States.
A new international scientific assessment by the Intergovern-
mental Panel on Climate Change recently concluded that "the
balance of evidence suggests a discernible human influence
on global climate."
Future Climatic Changes
For a given concentration of greenhouse gases, the resulting
increase in the atmosphere's heat-trapping ability can be pre-
dicted with precision, but the resulting impact on climate is more
uncertain. The climate system is complex and dynamic, with
constant interaction between the atmosphere, land, ice, and
oceans. Further, humans have never experienced such a rapid rise
in greenhouse gases. In effect, a large and uncontrolled planet-
wide experiment is being conducted.
General circulation models are complex computer simulations that
describe the circulation of air and ocean currents and how energy
is transported within the climate system. While uncertainties
remain, these models are a powerful tool for studying climate. As
a result of continuous model improvements over the last few
decades, scientists are reasonably confident about the link
between global greenhouse gas concentrations and temperature
and about the ability of models to characterize future climate at
continental scales.
Recent model calculations suggest that the global surface temper-
ature could increase an average of 1.6-6.3°F by 2100, with signif-
icant regional variation. These temperature changes would be far
greater than recent natural fluctuations, and they would occur
significantly faster than any known changes in the last 10,000
years. The United States is projected to warm more than the
global average, especially as fewer sulfate aerosols are produced.
The models suggest that the rate of evaporation will increase as
the climate warms, which will increase average global precipita-
tion. They also suggest increased frequency of intense rainfall as
well as a marked decrease in soil moisture over some mid-
continental regions during the summer. Sea level is projected to
increase by 6-38 inches by 2100.
Calculations of regional climate change are much less reliable
than global ones, and it is unclear whether regional climate will
become more variable. The frequency and intensity of some
extreme weather of critical importance to ecological systems
(droughts, floods, frosts, cloudiness, the frequency of hot or cold
spells, and the intensity of associated fire and pest outbreaks)
could increase.
Local Climate Changes
Over the last century, the average temperature near Albuquerque.
New Mexico, has decreased 0.8°F, and precipitation has increased
by up to 20% in many parts of the state. These past trends may or
may not continue into the future.
Over the next century, climate in New Mexico could experience
additional changes. For example, based on projections made by
the Intergovernmental Panel on Climate Change and results from
the United Kingdom Hadley Centre's climate model (HadCM2), a
model that accounts for both greenhouse gases and aerosols, by
2100 temperatures in New Mexico could increase by 3 °F in spring
(with a range of 1-5°F), 4°F in fall (with a range of 2-7°F), and 5°F
in winter and summer (with a range of 2-9°F). Precipitation is
estimated to decrease slightly (with a range of 0 to -10%) in
summer, to increase slightly infall (witha range of 0-10%), to
increase by 15% in spring (with a range of 5-25%), and to increase
by 30% in winter (with a range of 15-60%). Other climate models
may show different results, especially regarding estimated
changes in precipitation. The impacts described in the sections
that follow take into account estimates from different models. The
amount of precipitation on extreme wet or snowy days in winter is
likely to increase. The frequency of extreme hot days in summer
would increase because of the general warming trend. It is not
clear how the severity of storms might be affected, although
an increase in the frequency and intensity of winter storms is
possible. There also could be an increase in the frequency of
summer thunderstorms associated with monsoonal moisture
flow from the Gulf of Mexico.
Precipitation Trends From 1900 To Present
Trends/100 years
+20%
+10%
+5%
-5% O
-10% O
-20%
Source: Karl et al. (1996)
-------
Human Health
Higher temperatures and increased frequency of heat waves
may increase the number of heat-related deaths and the incidence
of heat-related illnesses. The elderly, particularly those living
alone, are at greatest risk. These effects have been studied only
for populations living in urban areas; however, even those in
rural areas may be susceptible.
Upper and lower respiratory allergies are influenced by humidity.
A 2°F warming and wetter conditions could increase respiratory
allergies.
Infected individuals can bring malaria to places where it does
not occur naturally. Also, mosquitoes in New Mexico can carry
malaria. If conditions become warmer and wetter, mosquito
populations could increase, thus increasing the risk of transmis-
sion if this and other diseases are introduced into the area.
Increased runoff from heavy rainfall could increase water-borne
diseases such as giardia, cryptosporidia, and viral and bacterial
gastroenteritides. Developed countries such as the United States
should be able to minimize the impacts of these diseases through
existing disease prevention and control methods.
Rodent-borne diseases are prevalent in New Mexico, and
upsurges of rodent populations have been associated with
extreme events and in particular the El Nino Southern Oscillation
phenomenon. In 1993, hantavirus pulmonary syndrome emerged
in New Mexico, and the deer mice that are the primary reservoir
for hantaviruses are prevalent in New Mexico. Long droughts
punctuated by heavy rains can decrease the predators (owls.
snakes, and coyotes) of rodents, and the heavy rains can
provide the rodents with added food supplies (grasshoppers
and pinon nuts).
Water Resources
Groundwater is the principal source of water for public, industrial.
and agricultural uses in New Mexico. Irrigation, the largest user of
water, relies on groundwater and surface water supplies. Except in
mountainous areas, many streams run dry at some time of the
year. Reservoirs on the larger perennial rivers, including the Rio
Grande, Pecos, and San Juan rivers, provide storage to reduce the
variation in streamflow and the severity of floods.
Much of streamflow in New Mexico results from spring and
summer rainfall and snowmelt in the mountains. In nonmoun-
tainous regions, runoff results from short, intense rainstorms. A
warmer climate could mean less winter snowfall, more winter rain.
and a faster, earlier spring snowmelt. This could result in higher
winter and spring flows and the inability to store flood waters for
use later in the summer. Additionally, without large increases in
rainfall, higher temperatures and increased evaporation could
lower lake levels and streamflows in the summer. Less water
would be available to distribute to the central and southern parts
of the state, where adequate supplies for irrigation and municipal
uses is a concern. In the densely populated middle Rio Grande
Valley, which includes Albuquerque, the availability of adequate
water to meet the needs of its growing population is a major
issue. During years of meager snowfall, many areas must supple-
ment surface water supplies with groundwater; however, less
spring and summer recharge could lower groundwater levels. This
could amplify problems in the eastern and southeastern parts of
the state, where groundwater levels are declining because of large
irrigation withdrawals, as well as in west-central New Mexico,
where groundwater development has increased to support
municipal, domestic, industrial, and agricultural uses. Lower flows
and higher temperatures could also impair water quality by
concentrating pollutants and reducing the capacity of streams to
assimilate wastes. The limited surface waters of New Mexico are
almost completely allocated through legal compacts and water-
rights agreements. Tribal water rights are also an important issue.
Changes in water availability could complicate the complex water
rights and allocation issues in New Mexico.
More rain could ease water competition, but it also could increase
flooding. Earlier, more rapid snowmelts could contribute to winter
and spring flooding, and more intense summer storms could
increase the likelihood of flash floods. Increased rains also could
increase erosion and pollution from runoff from mining areas, and
exacerbate levels of pesticides and fertilizers from runoff from
agricultural lands. Stream sedimentation is a major water quality
problem in New Mexico, as is contaminated runoff from grazing
lands, mining areas, urban areas, and irrigated fields.
Agriculture
The mix of crop and livestock production in a state is influenced
by climatic conditions and water availability. As climate warms.
production patterns could shift northward. Increases in climate
variability could make adaptation by farmers more difficult.
Warmer climates and less soil moisture due to increased evapora-
tion may increase the need for irrigation. However, these same
conditions could decrease water supplies, which also may be
needed by natural ecosystems, urban populations, industry.
and other users.
Understandably, most studies have not fully accounted for
changes in climate variability, water availability, crop pests.
changes in air pollution such as ozone, and adaptation by farmers
Changes In Agricultural Yield And Production
Irrigated Yield
Production
Wheat Sorghum Hay
• AT = 9°F; Aprecip. = 1%
Wheat Sorghum Hay
AT = 8°F; Aprecip. = 12%
Sources: Mendelsohn and Neumann (in press); McCarl
(personal communication)
-------
to changing climate. Including these factors could change
modeling results substantially. Analyses that assume changes
in average climate and effective adaptation by farmers suggest
that aggregate U.S. food production would not be harmed,
although there may be significant regional changes.
In New Mexico, production agriculture is a $ 1.6 billion annual
industry, two-thirds of which comes from livestock, mainly cattle.
More than one-half of the farmed acres are irrigated. The major
crops in the state are sorghum, wheat, and hay. Climate change
could reduce wheat yields by 10-30% and sorghum yields by
7-9% as temperatures rise beyond the tolerance levels of the crop.
Hay and pasture yields could fall by 4% or rise by 9%, depending
on how climate changes and the extent of irrigation. Farmed acres
could fall by 20-25% as a result of climate change. Livestock
production may not be affected, unless summer temperatures rise
significantly and conditions become significantly drier. Under
these conditions, livestock tend to gain less weight and pasture
yields decline, limiting forage.
Forests
Trees and forests are adapted to specific climate conditions.
and as climate warms, forests will change. These changes could
include changes in species composition, geographic range, and
health and productivity. If conditions also become drier, the
current range and density of forests could be reduced and
replaced by grasslands and pasture. Even a warmer and wetter
climate could lead to changes; trees that are better adapted to
these conditions, such as fir and spruce, would thrive. Under
these conditions, forests could become more dense. These
changes could occur during the lifetimes of today's children.
particularly if the change is accelerated by other stresses such
as fire, pests, and diseases. Some of these stresses would
themselves be worsened by a warmer and drier climate.
With changes in climate, the extent of forested areas in New
Mexico could change little or decline by as much as 15-30%.
The uncertainties depend on many factors, including whether
soils become drier and, if so, how much drier. Hotter, drier
weather could increase the frequency and intensity of wildfires.
Changes In Forest Cover
Current +10°F, +13% Precipitation
Conifer Forest
Broadleaf Forest
Savanna/Woodland
Shrub/Woodland
Grassland
Arid Lands
Sources: VEMAP Participants (1995); Neilson (1995)
threatening both property and forests. Drier conditions would
reduce the range and health of ponderosa and pinon-juniper
forests, and increase their susceptibility to fire. Grassland.
rangeland, and even desert could expand into previously forested
areas in the northern part of the state and those found at higher
elevations. Milder winters could increase the likelihood of insect
outbreaks and of subsequent wildfires in the dead fuel left after
such an outbreak. These changes would significantly affect the
character of New Mexico forests and the activities that depend on
them. However, increased rainfall could reduce the severity of
these effects.
Ecosystems
A wide variety of ecosystems are found in New Mexico.
including the Chihuahuan Desert, Great Plains grassland, Great
Basin shrub-steppe, pinon-juniper woodland, bosque riparian
forests and wetlands, ponderosa pine forests, mixed-conifer
montane forests, and subalpine forests and meadows. Narrow
strips of riparian vegetation throughout the state are extremely
important to wildlife, especially the endangered cactus ferrugi-
nous pygmy owl, southwestern willow flycatcher, masked
bobwhite quail, Mexican spotted owl, and southern nesting bald
eagle. Bitter Lake, in the southeastern part of the state, is an oasis
at the edge of the desert, providing habitat for snow geese.
sandhill cranes, endangered interior least terns, and thousands of
other birds. Mountaintop habitats in the Chihuahuan Desert are
isolated from one another and have remarkably different species
because their biotic communities have evolved in distinct ways
overtime. For example, more than 2,000 plant species thrive in
this area at the intersection of Arizona, New Mexico, and Mexico.
nearly 10% of all the species found in the United States.
The destruction of riparian areas, primarily through overwhelming
pressures for water resources and overgrazing, is the single most
important factor threatening and endangering many species of
fish and wildlife in New Mexico. For example, the Gila River is the
only U.S. river basin with all 47 of its freshwater fish species
extinct, listed as threatened or endangered, or recommended as
candidates of such listings. Climate change could exacerbate
these existing threats. The narrow riparian habitat bands would
be greatly influenced by decreased water availability. This could
ultimately alter avian species number and community composi-
tion, with the loss of many species that rely on riparian vegeta-
tion for nesting and food resources, such as the endangered
southwestern willow flycatcher and Mexican spotted owl. Warmer
water temperatures could adversely affect habitat conditions for
already endangered fish, and favor the spread of exotic species
that are imperiling the survival of New Mexico's native fish
species. In desert areas, many plants and animals already live
near their tolerance limits and may be unable to survive under
hotter conditions. Mountaintop island habitats are equally
vulnerable to changing conditions. Whereas other ecosystems
may have room to migrate in response to warming temperatures.
those in mountain areas could have little room to move upslope.
For further information about the potential impacts of climate
change, contact the Climate and Policy Assessment Division
(2174), U.S. EPA, 401 M Street SW, Washington, DC 20460, or
visit http://www. epa.gov/globalwarming/impacts.
------- |