OLR Research Report

September 16, 2010




By: Kevin E. McCarthy, Principal Analyst


This memo addresses climate change and its potential implications for Connecticut's water and energy utilities. It describes the current status of climate science, observed and projected climate trends in the Northeast, and how trends could affect these utilities.

As defined by the Intergovernmental Panel on Climate Change (IPCC), climate change is a statistically significant variation in either the average state of the climate or its variability, persisting for an extended period (typically decades or longer). Climate thus differs from weather, which typically occurs over much shorter periods. Climate change may be due to natural internal processes or external forces, or to persistent manmade changes in the atmosphere's composition or in land use. There are several useful introductions to how and why the climate changes, including those produced by the National Academy of Science (http://dels-old.nas.edu/dels/rpt_briefs/climate_change_2008_final.pdf), and the National Center for Atmospheric Research (www.eo.ucar.edu/basics/index.html).

Much of the information in this report is taken from (1) the 2010 report to the legislature of the Adaptation Subcommittee of the Governor's Steering Committee on Climate Change (Adaptation Subcommittee), available online at http://ctclimatechange.com/wp-content/uploads/2010/05/Impacts-of-Climate-Change-on-CT-Ag-Infr-Nat-Res-and-Pub-Health-April-2010.pdf and (2) a 2008 issue of Drinking Water Research addressing climate change and water utilities, available online at


There is a general consensus, although not unanimity, among scientists who study climate and its impacts on the environment and people that:

1. the global climate has been changing in recent decades, with most areas experiencing warmer air and water temperatures;

2. sea levels have been rising correspondingly and there have been changes in precipitation patterns;

3. most of these changes are attributable to human activities, notably the combustion of fossil fuels producing carbon dioxide (CO2) and other greenhouse gases (GHG);

4. continuation of current GHG emission trends will accelerate these changes; and

5. on balance, these changes have negative implications for people and the environment.

Since 1970, the annual mean (average) air temperature in the northeastern United States has increased by 2 F, with winter temperatures rising twice this much. (For comparison, historically the annual mean temperature in Hartford has been about 2 F warmer than in Buffalo, New York.) This warming has been accompanied by more frequent days over 90 F, increasing water temperatures and sea level, and an increase in heavy downpours and other extreme weather events.

We have not found any analyses of climate change specific to Connecticut, but a study of climate in the New York City metropolitan region (which includes much of Connecticut) projects that mean annual temperatures will increase an additional 1.5 to 3 F by the 2020s, 3 to 5 F by the 2050s, and 4 to 7.5 F by the 2080s. The study, which used the IPCC models, also projects further increases in sea level and in the frequency and intensity of extreme weather events. The Adaptation Subcommittee used this study as the basis for its report to the legislature.

Some of the implications of climate change for utilities are positive. For example, rising temperatures in the winter will decrease demand for heating energy and thus consumer expenditures during this season. Rising temperatures will also lengthen the construction season, allowing more time to develop and maintain energy and water infrastructure. Increased precipitation will increase power production from hydroelectric plants.

However, most of the implications of climate change for water and energy utilities are negative. In some cases, the impacts are due to continuation of current trends. For example, higher air temperatures reduce the amount of water that is available during the summer, the period of peak demand, due to greater evaporation from surface water bodies. Higher temperatures also increase peak demand for electricity, primarily due to greater demand for air conditioning, which can require increases in energy infrastructure investment whose costs are recovered in rates. Increased peak demand can also increase the likelihood of outages as transmission and distribution systems become stressed.

In other cases, the impact of climate change on utilities is the result of certain events becoming more common. For example, the increased likelihood of droughts has implications for water supply. Finally, long-term trends and increased probabilities of adverse events can interact. For example, climate models project that the sea level will continue to rise at the same time that the probability of coastal storms increases. The combination of these factors can lead to enhanced coastal flooding, threatening power plants and other energy infrastructure located on Long Island Sound and its estuaries.

In the future, climate change may become a consideration in utility planning, facility siting, and ratemaking. For example, changes in precipitation patterns may affect water supply planning. Increased sea levels may require the relocation of utility facilities located in vulnerable locations such as coastal flood plains. Increased air temperatures may shorten the life of electric distribution equipment, decreasing the amount of time over which their capital costs can be recovered in rates.

Scientists are uncertain about certain aspects of climate change that are relevant to utilities, most notably how quickly the earth is warming. As noted above, the model used by the Adaptation Subcommittee has a 3.5 F range for its temperature projection for the end of this century. This is about the difference in the current mean annual temperature between Hartford and Kansas City, Missouri. There are also disagreements on a number of issues, such as whether climate change

will increase the frequency or severity of hurricanes. In addition, work is just now starting on developing climate models for geographical areas as small as Connecticut.


A wide range of scientific bodies have issued statements on climate change over the past decade based on empirical studies and projections. The degree of confidence and specificity expressed in these statements has increased over time.

In the most comprehensive analysis to date, IPCC found in 2007 that:

warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level.

Significantly, IPCC added:

Most of the observed increase in global average temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic [man-made] GHG concentrations. … Continued GHG emissions at or above current rates would cause further warming and induce many changes in the global climate system during the 21st century that would very likely be larger than those observed during the 20th century… Altered frequencies and intensities of extreme weather, together with sea level rise, are expected to have mostly adverse effects on natural and human systems.

http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_spm.pdf (emphasis in original).

Subsequent statements by scientific bodies have come to similar conclusions. In 2009, the national science academies of 13 countries, including the U.S., Canada, China, Great Britain, Germany, Japan, and Russia, found that “climate change is happening even faster than previously estimated; global CO2 emissions since 2000 have been higher than even the highest predictions, Arctic sea ice has been melting at rates much faster than predicted, and the rise in the sea level has become more rapid.” www.nationalacademies.org/includes/G8+5energy-climate09.pdf.

In May 2010, the U.S. National Research Council, which consists of the National Academy of Sciences and associated organizations, found that:

Global warming is closely associated with a broad spectrum of other climate changes, such as increases in the frequency of intense rainfall, decreases in snow cover and sea ice, more frequent and intense heat waves, rising sea levels, and widespread ocean acidification. Individually and collectively, these changes pose risks for a wide range of human and environmental systems, including freshwater resources, the coastal environment, ecosystems, agriculture, fisheries, human health, and national security, among others.


According to the State of the Climate report published by the National Oceanic and Atmospheric Administration (the parent agency of the National Weather Service) in July 2010, the scientific evidence that the world is warming is “unmistakable.” The report noted that:

global average surface temperatures during the last three decades have been progressively warmer than all earlier decades, making 2000-09 (the 2000s) the warmest decade in the instrumental record. The 2000s were also the warmest decade on record in the lower troposphere, being about 0.6C warmer than the 1960s and 0.2C warmer than the 1990s.


Among the other scientific organizations that have adopted positions consistent with the above discussion are the American Academy for the Advancement of Science, the American Chemical Society, the American Institute of Physics, the American Geophysical Society, the American Institute of Biological Sciences, and the American Medical Association. In several cases, these organizations specifically referenced the findings of the 2007 IPCC report.


There is substantial regional variation in observed climate changes in the United States and elsewhere. This variation is seen in precipitation and temperature, among other things. As discussed below, the variation has implication for Connecticut's utilities. For example, annual average precipitation increased by 10%-20% over most of the northeastern United States over the past 50 years but fell by 10%-25% over most of the Southeast in this period. It appears that this difference is largely due to increased air temperatures moving the jet stream north, causing storms to track northward. There is similar variability in temperatures over shorter periods. While the first half of 2010 was one of the hottest such periods in the Northeast since records began being maintained in the late 19th century (in Connecticut it was the 3rd hottest), it was cooler than normal during this period in the Southeast.

There are also significant regional differences in projected climate change. For example, the Global Change Research Program, a consortium of 13 federal agencies, projects that precipitation and runoff are likely to continue to increase in the Northeast and Midwest, notably in winter and spring, but decrease in the West (especially the Southwest) in spring and summer.

The program also has found that, since 1970, the annual average temperature in the Northeast has increased by 2F, with winter temperatures rising twice this much. It found that:

this warming has resulted in many other climate-related changes including more frequent very hot days, a longer growing season, an increase in heavy downpours, less winter precipitation falling as snow and more as rain, reduced snowpack, earlier break-up of winter ice on lakes and rivers, earlier spring snowmelt resulting in earlier peak river flows, rising sea surface temperatures, and rising sea level.


We have found no projections of climate change that are specific to Connecticut. However, projections have been made by the New York Panel on Climate Change (NPCC) for the New York City region, which includes much of Connecticut. NPCC used global climate models based on methods and emissions scenarios from the IPCC to develop projections for this region. The report projects increases in temperature, precipitation, sea level and extreme weather events in 2020, 2050 and 2080. NPCC used a combination of 16 models and three emissions scenarios to produce data for temperature, precipitation, and extreme weather events. NPCC also added a “rapid ice melt” scenario in light of the recent acceleration of Arctic melting. The report is available at


The report projects that warmer temperatures are extremely likely in the region. It projects mean annual temperatures in the region to increase 1.5 to 3 F by the 2020s, 3 to 5 F by the 2050s, and 4 to 7.5 F by the 2080s. It also projects that the warming will be greatest in the winter and that northwestern Connecticut will see somewhat more warming and southeastern Connecticut somewhat less warming than the rest of the state. The models project that there will be 29 to 45 days per year when the temperature exceeds 90 F by mid-century and 37 to 64 such days by the end of the century, compared to the current average of 14 days per year.

Total annual precipitation in the region will probably increase. The models project that mean annual precipitation will increase by up to 5% by the 2020s, up to 10% by the 2050s, and 5% to 10% by the 2080s. The study notes that the models are in less agreement about the direction of precipitation change, and precipitation is characterized by large variability between years, making these projections more uncertain than those for temperature. At the same time, the models project that it is very likely that droughts will increase in frequency, duration, and intensity.

The study finds that rising sea levels are extremely likely. The models project that annual mean sea level will increase 2 to 5 inches by the 2020s, 7 to 12 inches by the 2050s, and 12 to 23 inches by the 2080s. Under the scenarios where Arctic ice melts rapidly, the sea level rise could be 41 to 55 inches by the last part of the century. The models project that it is very likely that sea-level rise will cause coastal flooding associated with storms to increase.

The Adaptation Subcommittee used this study as the basis of its 2010 report to the legislature. It found the NPCC models are based on sound science and use baseline data that is very similar to Connecticut weather data. The subcommittee also considered a less comprehensive study prepared in 2007 by the Northeast Climate Impacts Assessment, a collaboration between the Union of Concerned Scientists and a team of independent scientists. That study projected that the number of days when the temperature exceeds 100 F in Hartford would increase from an average of two days per year now to 28 days per year if current GHG emission trends do not change.


Water Utilities

Several aspects of climate change are likely to affect water utilities, notably changes in precipitation patterns, increased sea level, and warmer air and water temperatures. As noted above, regional models indicate that precipitation in the Northeast will likely increase. At the same time precipitation is likely to become more irregular, with both more frequent downpours and droughts. In its report to the legislature, the Adaptation Subcommittee found that:

more frequent and intense droughts will decrease the quantity of available water, while increased precipitation and extreme precipitation events [e.g., downpours] will increase stormwater and wastewater volumes, and thus decrease water quality from related pollutant loads. Sea level rise also can impact Connecticut's water supply by increasing salt intrusion in fresh water resources, including the numerous private wells along the shoreline. The projected combination of sea level rise and increased precipitation could lead to higher groundwater levels, which would limit the usefulness of infiltration galleries and other best management practices (BMPs) used to offset peak runoff impacts from stormwater. Increased precipitation will increase stormwater and wastewater, which could overwhelm existing stormwater and wastewater infrastructure, including sewers, combined sewer systems, sump pumps and pump stations, and thus decrease water quality. In addition, higher groundwater tables may contribute to contaminant leaching from landfills, further decreasing water quality.

More frequent downpours can also increase turbidity (murkiness) and sedimentation in surface water sources, which can create public health problems by reducing the quantity and quality of drinking water.

Increased air temperatures in the summer lead to increased demand, both for human consumption and other uses such as agriculture. Increased air temperature causes the snowpack to melt earlier, which can decrease the amount of water available during the summer, when demand peaks. Rising air temperatures also cause water in reservoirs and other surface drinking water sources to evaporate more readily.

Increased water temperature leads to when increased eutrophication in surface sources. Eutrophication occurs algae and other biota grow at a faster than usual rate. When they die, their decomposition reduces the oxygen level of the water which can lead to fish kills. The air and water temperature changes can also affect vegetation in the watershed, which can alter recharge of groundwater aquifers and change the quantity and quality (e.g., alkalinity) of runoff into surface waters. While eutrophication primarily affects water utilities, by impairing water quality, it can also affect power generators that use surface water sources for cooling their power plants.

Rising sea level increase salt water intrusion into groundwater aquifers, thereby reducing their availability as drinking water supply sources and increasing the salinity of those surface water sources that flow into the sea. Both can increase the need for bromide in water treatment and can require desalination. In addition, rising sea levels can increase the risk of direct storm and flood damage to and corrosion of water utility facilities.

Energy Utilities

Although many of the effects of climate change on the energy sector have not been well studied, some have clear implications for energy production and use. For instance, rising temperatures are expected to increase energy needed for cooling and reduce energy needed for heating. Research on the effects of climate change on energy demand has largely been limited to impacts on energy use in buildings. These studies find that the demand for cooling energy increases 5% to 20% per 1.8F (1C) of warming, and the demand for heating energy drops 3% to 15% per 1.8F of warming. These ranges reflect different assumptions about factors such as the rate of market penetration of improved building equipment technologies. Nearly all of the cooling of buildings is provided by electricity, while the vast majority of heating is provided by natural gas and oil. Since it takes nearly three British Thermal Units (BTU) of energy from oil or natural gas to produce a BTU of electricity, the projected increase in air temperature will increase overall demand for and expenditures on energy.

National studies project that temperature increases due to climate change are very likely to increase peak demand for electricity in most regions. An increase in peak demand can lead to a disproportionate increase in energy infrastructure investment for new power generation or import capacity, whose costs are ultimately recovered in rates. It can also increase the likelihood of outages as the transmission and distribution systems become stressed. On the other hand, higher air temperatures lengthen the construction season, allowing major capital projects to be completed more quickly in some cases.

The efficiency of fossil fuel and nuclear power plants is sensitive to ambient air and water temperatures; higher temperatures reduce power outputs by affecting the efficiency of power generation. Although this effect is not large in percentage terms, even a small change could significantly affect electric power supply. Higher air temperatures can also reduce the expected life span of certain electric equipment, such as transformers.

Many energy facilities in Connecticut, including power plants and facilities that receive oil deliveries, are located near Long Island Sound and its estuaries. Rising sea levels are likely to lead to direct losses, such as equipment damage from flooding or erosion, and indirect effects, such as the costs of raising vulnerable assets to higher levels or building new facilities farther inland. The East Coast has been identified as particularly vulnerable to sea-level rise because the land near the coastline is relatively flat. In addition, extreme precipitation events, such as ice storms, can damage energy transmission lines and increased groundwater levels may erode underground structures.

The Adaptation Subcommittee notes that while the incremental rise in sea level directly threatens the viability and integrity of energy systems, the devastation of storm surges from hurricanes or major Nor'easters, are of more immediate concern. Many power plants in Connecticut are located along the coast, making them susceptible to the combination of sea level rise and storm surge. One plant in Bridgeport already experiences some site flooding when high tides coincide with the moon being closest to the earth in its orbit. If sea level rise accelerates due to more rapid melting of polar ice caps, the effects of a major storm would be compounded, reaching to higher elevations than under current sea level conditions.