Climate in Context

The region of the Northeast is unique in that weather occurring around much of the country eventually makes its way there. Because of the dominant southwest to northeasterly flow of the jet stream, storm events—hurricanes, nor'easters, mid-latitude cyclones, Alberta clippers—commonly combine with tropical, polar, and arctic air masses from northern and southern regions, affecting portions of the Northeast.

These weather patterns may lead to floods, droughts, heat waves, and severe storms, accentuating the significant weather variability of the region. The Northeast also receives high concentrations of chemical pollutants from neighboring regions, impacting air quality, visibility, and precipitation (in the form of acid rain). In a sense, the Northeast is downwind from the rest of the country—and thus has a unique environmental vulnerability.

Warmer, Wetter

Recent meteorological studies and climate assessments based on climate variables and indicators have produced compelling evidence that the region has been warming over the past century:

• Increase in temperatures. Temperatures have risen as much as 4°F (2°C) along coastal margins from the Chesapeake Bay through Maine.
• Greater precipitation. Twenty percent more precipitation now occurs in much of the Northeast region. Extremes appear to be increasing, while the amount of land area experiencing drought appears to be decreasing.
• Decreased snow period. The interval marking the first and last dates of snow on the ground decreased by seven days in the past fifty years. In some areas, the number of days with snow on the ground decreased from sixteen to thirty days. The 1990s had significant winter precipitation events, including many heavy snowfalls and major ice storms, while winter temperatures were mild.
• Earlier onset of the growing season. The growing season begins eight days earlier than in 1874. From 1965–2001, the first lilac blooms edged earlier by approximately one day/decade. Apples and grapes arrived four to eight days earlier. In certain localities (Atlantic City, New Jersey, for example) the growing season has lengthened five weeks.
• A shift in river and lake behavior. Earlier high-spring river flows are now the norm. The number of days of ice-affected flow for both lakes and rivers has decreased significantly in the past 100 years. Since 1850, ice-out dates (the day in spring most of the ice has broken up) are earlier. Ice-in dates (the day in winter when most of the lake has frozen over) are taking place later or not at all—for Lake Champlain, just thirty-one times, eleven of which since 1970.
• Elevated Sea Surface Temperature (SST). Temperatures in the Northeast's Gulf of Maine and South Shore of New England have risen 1.1°F and 1.6°F, respectively, since 1860.
• A rise in sea level. Sea level measured at ports has risen over the past 150 years, due to natural processes and human influences.

Mixed Forecast Ahead

The Northeast has some of the lowest rates of anticipated warming in the United States. Winter minimum temperatures are forecast to change the most, with increases ranging from 4 to 5°F (Hadley Climate Model) to as much as 9°F (Canadian Climate Model) by 2100. The largest increases are expected in coastal regions. Maximum temperatures may increase much less, but again the largest changes are likely to occur in winter.

Concerning precipitation, scenarios are wide-ranging. Predictions range from a roughly 25% increase on average for the entire region to—perhaps—little change. Precipitation variability in the coastal areas of the Northeast is likely to increase. As for the frequency and intensity of winter storms, models provide contrasting scenarios for change.

As for the future composition of forests in the Northeast, contrasting views prevail. Both imply noteworthy changes:

• The Canadian Model scenario: The conifer forest of northern New England and much of the northeast mixed forest of New England, New York, and western Pennsylvania are projected to evolve into a more temperate deciduous-type woodland similar to that found today in southeastern Pennsylvania, Maryland, and northern Virginia.
• The Hadley Climate Model scenario: The conifer forest of northern New England would be replaced by northeast mixed forest.

These vegetation projections strongly reflect the differences in moisture and temperature projections in both climate model scenarios.

Climate Impacts

If the warming trend continues as predicted, what will be the effect on both abiotic and biotic environments, as well as humans? Some key potential climate change impacts to watch closely:

Abiotic (air, water, soils)

• Water quality of estuaries and bays negatively impacted by human land use practices and upstream industry, causing increased algal blooms, shading of deeper water, and limiting submerged aquatic vegetation
• Migration or loss of key species due to changes in water salinity and temperature
• Increasing costs of replenishing beaches damaged by storms and high sea level
• Declining wetlands causing marsh loss and submerged protective barrier islands, due to rising sea level
• Coastal erosion from extreme weather events and sea level rise
• More frequent "flash" floods due to increased land development (peak rain flow reached more quickly when paved surfaces fail to absorb runoff from rainfall)
• Shorter ice season affecting rivers and lakes

Biotic (plants and animals)

• Northward migration of the lobster population (a key issue for New England)
• Encroachment of habitats of migratory birds, due to rising sea level
• Trout populations constrained from increased water temperatures
• Proliferation of invasive species due to climate changes
• Evolution of forest species composition from conifer to deciduous or mixed
• Northward displacement of maple trees, causing migration of the maple syrup industry from New England to Canada
• Growing tree vulnerability to insects, fires (from drought), extreme weather, and invasive species
• Limited spectrum of leaf color and change in timing of the leaf drop, affecting the fall foliage tourism industry

Human

• Personal safety and property at greater risk from extreme weather events such as ice storms, severe flooding, nor'easters, hurricanes, and drought
• Urban flooding of transportation hubs—airports, subways, highways, road and rail tunnels—due to rising sea levels and storm surges
• Increasing risk of Lyme disease and West Nile Virus from sprawling vector populations (deer and mice; and mosquito), resulting from land development
• Increased health risks for vulnerable populations because of diminished air quality
• Mounting economic pressures on climate-dependent industries; for example, ski areas maintaining adequate snow pack, and dairy industry adapting to higher air conditioning costs
• Greater demands on water supply, quality, and delivery

From Research to Action

Long-term observations of the atmosphere, biosphere, oceans, and snow and ice have provided valuable input into an assessment of the state of the climate of the Northeast. The results reveal a gradual warming trend over the last century or so, and model forecasts suggest this trend will continue. While more research is required to better understand the reasons for our changing climate, additional indicators to be collected in the future can report on not only changes in the region's climate, but also the effect of these changes on the region's environment, economy, and quality of life.

Climate awareness is key. Understanding the potential impacts from climate change can be instrumental in helping governing bodies deal effectively with climate-related situations, especially those that depend on identifying and prioritizing vulnerable facilities and populations.

References

Barron, E. et al. 2000. Potential Consequences of Climate Variability and Change for the Northeastern United States. U.S. National Assessment of the Potential Consequences of Climate Variability and Change. Mega-Region: Northeast.
http://www.usgcrp.gov/usgcrp/Library/nationalassessment/04NE.pdf.

Carter, L., Rock, B., Fisher, A. 2000. U.S. National Assessment of the Potential Consequences of Climate Variability and Change. Educational Resources. Regional Paper: The Northeast.
http://www.usgcrp.gov/usgcrp/nacc/education/northeast/.

Moore, B., Rock, B. 1998. New England Regional Climate Change Impacts Workshop (NECCI) Summary Report. U.S. National Assessment of the Potential Consequences of Climate Variability and Change. Region: New England. September 3-5, 1997, Durham, N.H.: University of New Hampshire.
http://www.necci.sr.unh.edu/necci-report/sum-rept.pdf.

National Assessment Synthesis Team. U.S. Global Change Research Program. 2000. Climate Change Impacts of the United States. The Potential Consequences of Climate Variability and Change. Overview: Northeast.
http://www.usgcrp.gov/usgcrp/Library/nationalassessment/5NE.pdf.

Rosenzweig, C., Solecki, W. et al. 2000. Climate Change and a Global City: An Assessment of the Metropolitan East Coast Region. U.S. National Assessment of the Potential Consequences of Climate Variability and Change. Region: Metro East Coast.
http://metroeast_climate.ciesin.columbia.edu/reports/assessmentsynth.pdf.

Wake, C. et al. 2005. Indicators of Climate Change in the Northeast 2005. The Climate Change Research Center, Durham, N.H.: University of New Hampshire.
http://cleanair-coolplanet.org/information/pdf/indicators.pdf.