October 6, 2010
OLR BACKGROUNDER: CLIMATE CHANGE AND TRANSPORTATION
By: Kevin McCarthy, Principal Analyst
This memo addresses climate change and its potential implications for Connecticut's transportation systems (road, rail, aviation, and marine). It describes the current status of climate science, observed and projected climate trends in the Northeast, and how trends could affect these systems. OLR report 2010-R-0337 provides similar information regarding the potential impacts of climate change on the state's energy and water 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 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; (2) a 2008 report by the Transportation Research Board (TRB) on the implications of climate change on transportation systems, available at http://onlinepubs.trb.org/onlinepubs/sr/sr290.pdf; (3) Global Climate Change Impacts in the United States, published in 2009 by the interagency U.S. Global Change Research Program, and available at http://downloads.globalchange.gov/usimpacts/pdfs/transportation.pdf;and (4) a study by Columbia University of the impacts of climate change in the New York/New Jersey/Connecticut region that focuses on the impacts of sea level rise on transportation and other infrastructure, available at http://metroeast_climate.ciesin.columbia.edu/infrastructure.html.
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 risen 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 transportation systems are positive. For example, rising temperatures in the winter will decrease overall snowfall and reduce the cost of snow removal. These phenomena will also improve the mobility and safety of passenger and freight travel through reduced winter hazards. Reduced levels of snow and ice will lessen harmful environmental impacts from the use of salt and chemicals on roads and bridges. Rising temperatures will also lengthen the construction season, which will facilitate the development and maintenance of all types of transportation infrastructure.
However, many of the implications of climate change for transportation systems are negative. In some cases, the impacts are due to continuation of current trends. For example, transportation infrastructure in coastal areas is increasingly vulnerable to sea-level rise. In other cases, the impact of climate change on transportation infrastructure is the result of certain events becoming more common. For example, flooding from increasingly intense downpours will increase the risk of disruptions and delays in air, rail, and road transportation. 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 roads, rail lines, and other infrastructure located on Long Island Sound and its estuaries.
There are uncertainties in the understanding of climate change, 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.
STATE OF THE SCIENCE
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 reached 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 level, 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 in July 2010 by the National Oceanic and Atmospheric Administration (the parent agency of the National Weather Service), found that the scientific evidence that the world is warming is “unmistakable.” It 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 0.6°C warmer than the 1960s and 0.2°C 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.
CLIMATE CHANGE IN CONNECTICUT AND THE NORTHEAST
There is substantial regional variation in observed climate changes in the United States and elsewhere. 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 on record (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. The impact of sea level increases are projected to be less significant in New England, where the earth's surface is rising due to uplift (the continued rebounding from the retreat of glaciers during the last Ice Age) than along the Gulf Coast, where the shoreline is subsiding. In addition, 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 has found that, since 1970, the annual average temperature in the Northeast has increased by 2°F, 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 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 temperature, precipitation, sea level rise and extreme weather events for 2020, 2050 and 2080. NPCC used a combination of sixteen models and three emissions scenarios to produce data for temperature, precipitation, and extreme weather events. NPCC also added a “rapid ice melt” scenario to the IPCC scenarios to produce a projection of future sea level rise in the region 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. The models project 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 the 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 storm-related coastal flooding 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.
IMPLICATIONS FOR TRANSPORTATION SYSTEMS
The 2008 TRB study found that climate change affects transportation mainly through changes in (1) weather extremes, such as very hot days or severe storms; (2) changes in climate extremes, such as increases in the probability of intense precipitation events (downpours and blizzards) and extended droughts; and (3) sea level rise. It notes that the transportation system was built for typical weather and climate, including a reasonable range of extremes. As a result, moderate changes in climate averages have little effect on transportation infrastructure or operations because the system is designed to accommodate changing weather conditions. But changes in weather and climate extremes can have a considerable impact on transportation, especially if they push environmental conditions outside the range for which the system was designed.
The study noted that the impacts of climate change will likely vary by mode of transportation and region of the country, and some impacts will be positive. But it concludes that the impacts will likely be widespread and costly in both human and economic terms and require significant changes in the planning, design, construction, operation, and maintenance of transportation systems. Similarly, the Adaptation Subcommittee concluded that there was a high risk of negative impacts from climate change, notably precipitation changes, by the middle of this century. It cited a series of factsheets prepared by the Department of Environmental Protection, entitled Facing our Future: Adapting to Connecticut's Climate Change. The infrastructure factsheet identified river and coastal flooding as the primary environmental threats to the state's infrastructure. According to the 2008 TRB study, the most immediate impact of more intense precipitation will be increased flooding of coastal roads. Expected sea level rise will aggravate this flooding because storm surges will build on a higher base, reaching farther inland. The Columbia University study found that while sea level is expected to rise by less than 3 feet by 2090, this increase will likely triple the frequency of coastal flooding.
According to the TRB study, the longevity of transportation infrastructure, the long-term nature of climate change, and the potential impacts identified by recent studies warrant attention to climate change in planning new or rehabilitated transportation systems. The vulnerability of transportation systems to these impacts has not been thoroughly studied, nor has it been widely considered by decision makers in planning, designing, constructing, retrofitting, and operating the transportation infrastructure.
The Adaptation Subcommittee noted that the options for adapting infrastructure to climate change include: (1) relocation to lower risk areas; (2) re-engineering to new, more protective standards; and (3) implementing mitigation techniques such as watershed management to reduce the impact of flooding. It observed that not every technique will be practicable or even applicable to all types of infrastructure, and, in many cases, adapting existing infrastructure may be more problematic and expensive and less effective than incorporating adaptation strategies into new construction.
The Columbia University study, which covered Fairfield, Litchfield, and New Haven counties as well as the rest of the New York metropolitan region, found that that (1) many transportation facilities have components are at elevations of only 6 to 20 feet above current sea level, exposing them to storm surges that have been modeled to reach heights in excess of 20 feet and (2) effective mitigation strategies against the known risks have not been developed, except for emergency evacuation planning. It projected that for the two thirds of the facilities in the region that have components that are at or below 10 feet above the current sea level, flooding by the end of this century may occur at least once every decade, and for some facilities every few years.
Roads and Bridges
In Connecticut and other northern states, climate change will likely have positive and negative impacts on roads and bridges. Warmer winters will reduce snow and ice removal costs, lessen adverse environmental impacts from the use of salt and chemicals on roads and bridges, extend the construction season, and improve the mobility and safety of passenger and freight travel through reduced winter hazards.
On the other hand, more freeze-thaw conditions are projected to occur, creating frost heaves and potholes on road and bridge surfaces and resulting in load restrictions on certain roads to minimize the damage. Longer periods of extreme heat in summer can damage roads in several ways, including softening of asphalt that leads to rutting from heavy traffic. Sustained air temperature over 90°F is a significant threshold for such problems. Increases in very hot days and heat waves may limit construction activities due to health and safety concerns for highway workers. The U.S. Occupational Safety and Health Administration notes that heat stress for moderate to heavy work begins when the temperature humidity index reaches 80°F.
Changes in precipitation also affect roads and bridges. Civil engineers estimate the probabilities of intense rain storms to design culverts, storm water drainage systems, and roadbeds. Projected increases in intense precipitation events will require updating design specifications to provide for greater capacity and to cope with the increased frequency of such events, increasing system costs. In addition, many coastal cities have parking garages that are partially below grade, which are projected to experience more frequent and severe flooding.
Many of the implications of climate change for rail systems are similar to those for roads and bridges. The Global Change Program's study projects more frequent flooding and interruptions in travel on coastal and low-lying rail lines due to storm surge, potentially requiring changes to minimize disruptions. In 2010, flooding in Rhode Island resulting from a downpour forced Amtrak to suspend service between New York and Boston. Higher sea levels and storm surges will also undermine bridge supports. The lowest elevation on the New Haven line is 9.8 feet above sea level, according to the Columbia University study. The study notes that weak (category 1) hurricanes can create a storm surge of up to 8.4 feet in parts of Fairfield County at the current sea level.
Extreme heat can cause deformities in rail tracks, causing problems ranging from speed restrictions to derailments. Air temperatures above 100°F can lead to rail equipment failure. Extreme heat also causes thermal expansion of bridge joints, adversely affecting bridge operations and increasing maintenance costs.
The projected climate change would have both positive and negative impacts on aviation. Airports in Connecticut and other northern states are likely to benefit from reduced cost for snow and ice removal and less salt and chemical use. Airlines could benefit from reduced need to de-ice planes. Fewer extremely cold days will reduce restrictions on baggage crews.
On the other hand, the 2008 TRB study notes that the increased frequency of extreme heat is likely to cause runways to buckle. Extreme heat can also reduce aircraft lift; heat decreases the density of air so that there is less mass flowing over the wing and it becomes harder to airplanes to take off and remain airborne.
The study also noted that runways of airports in coastal zones (in Connecticut, Tweed New Haven and Groton New London) are particularly
vulnerable to flooding and erosion from increased intense precipitation and, in the longer term, from sea level rise. There are also potential spill-over effects from the impact of climate change on nearby major airports. For example, much of LaGuardia and Newark airports could be subject to flooding from storm surges later in this century.
Warming winter temperatures, particularly in northern coastal areas, could benefit marine transportation. Fewer days below freezing would reduce problems with ice accumulation on vessels, decks, riggings, and docks; the occurrence of dangerous ice fog; and the likelihood of ice jams in ports.
On the other hand, climate change is projected to increase the frequency and intensity of storm surges. Storm surge is the abnormal rise in sea level above the level of the normal or astronomic tide that accompanies a hurricane or other intense storm such as a nor'easter. The 2008 TRB report notes that storm surge is of great concern to port operations, mooring facilities, and moored vessels, as well as to coastal infrastructure that is vulnerable to flooding.
The study found that coastal ports and harbor facilities will be affected by the combination of increased intense precipitation and sea level rise. Landside facilities will be particularly vulnerable to flooding from an increase in intense precipitation events and to the impacts of higher tides and storm surges from rising seas. Sea level is an important consideration at docks and container berths for clearance of dock cranes and other structures. Changes due to increased intense precipitation and sea level rise could require some retrofitting of facilities. The study found that these changes are likely to result in increased weather-related delays and periodic interruption of shipping services.