United States Environmental Protection Agency Office of Policy, Planning and Evaluation (2111) EPA 230-F-97-008g September 1997 vxEPA Climate Change And Connecticut 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 under way. 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 Solar radiation passes through the clear atmosphere 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. 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 businesses, 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 institu- tional developments. Several emissions scenarios have been developed based on differing projections of these underlying 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 since the late 19th century. The 9 warmest years 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 Source: U.S. Department of State (1992) ------- Global Temperature Changes (1861-1996) 03 0 I;-02 •0.4 •0.6 •0.8 f\ /x/Vv /\ / \f J /\ A / AA/W f* 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 Fora 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 uncertain- ties 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 tempera- ture and about the ability of models to characterize future climate at continental scales. Recent model calculations suggest that the global surface temperature could increase an average of 1,6-6.3°F by 2100, with significant 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 J 0.000 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, average temperatures in Storrs, Connecticut, have increased from 45.8°F (1892-1921 average) to 48.2°F (1966-1995 average), and precipitation in some locations has increased by 20%. Over the next century, Connecticut's climate may change even more. Based on projections given 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 Connecticut could increase about 4°F (with a range of 2-8°F) in all seasons. Precipitation is projected to increase by 10-20% (with a range of 0-40%), with slightly less change in spring and summer and slightly more in winter. The amount of precipitation on extreme wet (or snowy) days most likely would increase, but changes in the lengths of wet or dry spells are not clear. The frequency of extreme hot days in summer is expected to increase along with the general warming trend. It is not clear how severe storms such as hurri- canes would change, although an increase in the frequency and/or intensity of winter storms is possible. Precipitation Trends From 1900 To Present Trends/TOO years +20% + 10% +5% Source: Karl et al. (1996) ------- Climate Change Impacts Global climate change poses risks to human health and to terrestrial and aquatic ecosystems. Important economic resources such as agriculture, forestry, fisheries, and water resources also may be affected. Warmer temperatures, more severe droughts and floods, and sea level rise could have a wide range of impacts. All these stresses can add to existing stresses on resources caused by other influences such as population growth, land-use changes, and pollution. Similar temperature changes have occurred in the past, but the previous changes took place over centuries or millennia instead of decades. The ability of some plants and animals to migrate and adapt appears to be much slower than the predicted rate of climate change. 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. Connecticut, with its irregular, intense heat waves, may be especially susceptible. In Hartford, one study projects that a 2°F warming could increase heat-related deaths during a typical summer by about 20%, from close to 40 heat-related deaths per summer to near 50 (although increased air conditioning use may not have been fully accounted for). Winter-related deaths are expected to change very little if the temperature warms by 2°F. The elderly, particularly those living alone, are at greatest risk. There is concern that climate change could increase concentra- tions of ground-level ozone. For example, high temperatures, strong sunlight, and stable air masses tend to increase urban ozone levels. Air pollution also is made worse by increases in natural hydrocarbons emissions during hot weather. If a wanned climate causes increased use of air conditioners, air pollutant emissions from power plants also will increase. A 4°F warming in New York City, with no other change in weather or emissions, could increase concentrations of ozone, a major component of smog, by 4%. Similar increases could be expected in Connecticut. Currently, ground-level ozone concen- trations exceed national ozone health standards throughout the state. All of Connecticut is classified as a "serious" nonattainment area for ozone. Ground-level ozone has been shown to aggravate respiratory illnesses such as asthma, reduce existing lung func- tion, and induce respiratory inflammation. In addition, ambient ozone reduces crop yields and impairs ecosystem health. Warming and other climate changes could expand the habitat and infectivity of disease-carrying insects, thus increasing the potential for transmission of diseases such as malaria and dengue ("break bone") fever. Mosquitos flourish in some areas around Connecticut. Some can carry malaria, while others can carry Eastern equine encephalitis, which can be lethal or cause neuro- Future Sea Level Rise At New London 110 100 90 80 70 60 50 40 30 20 10 0 5% Chance - ' 50% Chance— 95% Chance - :,_ . . . x T J 2050 2100 2150 2200 Year Source: EPA (1995) logical damage. Lyme disease, which is carried by ticks, has increased in Connecticut. If conditions become warmer and wetter and thus support larger populations of mosquitos and ticks, these diseases may be transmitted more widely. In addition, warmer seas could contribute to the increased intensity, duration, and extent of harmful algal blooms. These blooms damage habitat and shellfish nurseries, can be toxic to humans, and can carry bacteria like those causing cholera. Brown algal tides and toxic algal blooms already are prevalent in the Atlantic. Warmer ocean waters could increase their occurrence and persistence. Coastal Areas Sea level rise could lead to flooding of low-lying property, loss of coastal wetlands, erosion of beaches, saltwater contamination of drinking water, and decreased longevity of low-lying roads, causeways, and bridges. In addition, sea level rise could increase the vulnerability of coastal areas to storms and associated flooding. Along much of Connecticut's coast, sea level already is rising 8 inches per century, and it is likely to rise another 22 inches by 2100. Connecticut's coastline contains valuable residential development and important wetlands ecosystems that would be vulnerable to flooding from sea level rise. In particular, Connecticut has extensive tidal flats and diverse nontidal fresh- water marshes. Because Long Island Sound may reduce wave action, some of these wetlands may be protected with a tempo- rary buffer from erosion. Connecticut's freshwater marshes, however, are likely to be harmed by saltwater intrusion. Cumulative costs through 2100 to protect Connecticut's coastline from a 20-inch sea level rise could be $0.5-$3 billion. ------- Water Resources Water resources are affected by changes in precipitation as well as by temperature, humidity, wind, and sunshine. Changes in streamflow tend to magnify changes in precipitation. Water resources in drier climates tend to be more sensitive to climate changes. Because evaporation is likely to increase with warmer climate, it could result in lower river flow and lower lake levels, particularly in the summer. In addition, more intense precipitation could increase flooding. If streamflow and lake levels drop, groundwater also could be reduced. The Connecticut River is susceptible to changes in winter snow accumulation, which would be reduced in a warmer climate. Peak spring streamflows in the Connecticut River could occur several weeks earlier if the climate were to warm about 4°F. The Housatanic and Thames rivers could see similar but smaller changes. Without increased precipitation, groundwater would decrease in a wanner climate, which would reduce Connecticut's aquifers. Changes In Agricultural Yield And Production Yield Production Silage Hay S3 AT = 7"F; Aprecip. = -1% Silage ~ Hay I AT = 10"F; Aprecip. = 12% Source: Mendelsohn and Neumann (in press); McCarl (personal communication) Agriculture The mix of crop and livestock production in a state is influenced by climatic conditions and water availability. As climate warms, production patterns will 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, and other economic sectors. Understandably, most studies have not fully accounted for changes in climate variability, water availability, and imperfect responses by farmers to changing climate. Including these factors could substantially change modeling results. Analyses based on changes, in average climate and which assume farmers effectively adapt suggest that aggregate U.S. food production will not be banned, although there may be significant regional changes. In Connecticut, agriculture is a S500 million annual industry. About one-twentieth of 1$ of total U.S. farm acres is in the state. The principal crops are silage and hay, and very little of the agricultural land is irrigated. Projections of changes in Connecticut yields are mixed; they could range from little change to decreases of almost 40%. Total acres farmed would remain about the same, but farm income could decrease by about 50%. Forests Trees and forests are adapted to specific climate conditions, and as climate warms, forests will change. These changes could include changes in species, geographic extent, and health and productivity. If conditions also become drier, the current range and density of forests could be reduced and replaced by grass- lands and pasture. Even a warmer and wetter climate would lead to changes; trees that are better adapted to these conditions, such as oaks and redwoods, would thrive. Under these conditions, forests could become more dense. These changes could occur during the lifetimes of today's children, particularly if they are 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 Connecticut could change little. However, a warmer climate could change the character of Connecticut's forests. Maple- dominated hardwood forests could give way to forests dominated by oaks and conifers, species more tolerant of higher tempera- tures. This change would diminish the brilliant autumn foliage as the contribution of maples declines. Across the state, as much as 30-60% of the hardwood forests could be replaced by warmer climate forests with a mix of pines and hardwoods. 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. ------- |