Northeast climate change | Catayst Spring 2007 | Union of Concerned Scientists

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Without deep cuts in heat-trapping emissions,
summers in New York near the end of the century may
feel as hot as Georgia summers do today. Fortunately,
it’s not too late to preserve the traditional character
of our northeastern states.

By Erika Spanger-Siegfried

The northeastern corner of the United States, from Pennsylvania and New Jersey northward to Maine, is famous for its bustling urban centers, quaint historic towns, snowy peaks, and sandy beaches. The region is also famous for weather that can change from one day (or even hour) to the next, but its general climate patterns have remained fairly consistent since Europeans first landed on these shores.

In recent decades, however, the characteristic climate of the Northeast has begun to change dramatically. Between 1970 and 2000 alone, summer temperatures rose about one degree Fahrenheit (ºF) and winter temperatures rose nearly 4 ºF. Spring is arriving sooner, summers are growing hotter, and winters are becoming warmer and less snowy.

Massachusetts' Migrating Climate,
1961-2099

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Changes in average summer heat index will strongly alter how summer feels to residents of the Northeast. Red arrows track what summers in Massachusetts could feel like over the course of the century if we follow a higher-emission pathway. Yellow arrows track what states could feel like on a lower-emission pathway, demonstrating that our emission choices make a difference.
Map: Amanda Wait/NonprofitDesign.com

These changes bear the fingerprint of global warming. Virtually all climate scientists agree that human activities, such as the burning of fossil fuels to generate electricity and power our cars, have led to increased atmospheric levels of heat-trapping gases (primarily carbon dioxide) that contribute to global warming.

Today’s Emissions, Tomorrow’s Climate

To determine the extent to which climate change could have an impact on this populous region, the Northeast Climate Impacts Assessment (NECIA), a collaboration between the Union of Concerned Scientists and a group of independent experts, used state-of-the-art climate models to project the future climate under higher-emission and lower-emission pathways. The findings indicate that the severity of future warming—and the quality of climate our children and grandchildren will inherit—depends on choices people in the Northeast and around the world make today: will we continue to rely heavily on fossil fuels, or will we transform our use of energy to be far more efficient and produce far less emissions?

Some climate changes are inevitable because of the continued effect of past emissions that are still in the atmosphere. For example, current and past emissions will likely cause winter temperatures to rise an additional 4 ºF over the next few decades, while summer temperatures will rise an additional 1 to 3 ºF. But our choice between a higher- or lower-emission pathway leads to starkly different climate futures by mid-century and beyond.

A higher-emission pathway, in which we continue to rely heavily on fossil fuels, could result in dramatic regional warming of 7 to 12 °F on average by the end of the century. To put such a change into perspective, a similar degree of cooling (compared with today’s temperatures) put the location of present-day New York City under a mile of ice. In short, the projected temperature increases could lead to a climate unrecognizable to current residents of the Northeast.

The Changing Face of Winter

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On a higher-emission pathway, far less of the Northeast will experience a typical snow season toward the end of the century. The red line in this map captures the area of the northeastern United States that, historically, has at least a dusting of snow on the ground for at least 30 days in the average year. The white area shows the projected retreat of this snow cover by century’s end, suggesting a significant change in the Northeast’s winter character.
Base map: Intraresearch d.b.a. MapMart

Warmer, Wetter Winters

With the approach of winter, communities and businesses ready themselves for snow, ice, and the deep chill of the season. But despite the occasional hard winter, the season has softened its grip on the Northeast in the past few decades. Less precipitation has fallen as snow, the snow that does fall has become more “slushy” on average, and warmer temperatures have melted the snow more quickly.

This warming is expected to continue across the region as a result of increased emissions. Under a higher-emission pathway, winter temperatures will rise between 4 and 7 °F by mid-century (2040–2069), and between 8 and 12 °F by the end of the century (2070–2099). If we choose a lower-emission pathway, the temperature rise will be significantly smaller (between 5 and 7.5 ºF by the end of the century). Winter precipitation is also expected to increase, but with higher temperatures this precipitation is more likely to take the form of rain than snow.

In addition, the number of snow-covered days is projected to decline in all of the northeastern states under a higher-emission pathway—even in the historically snowy northern reaches of the region. This would fundamentally change the winter landscape (see the figure, "The Changing Face of Winter"). By contrast, lower emissions would result in significantly smaller reductions in snow-covered days.

Summer in the City: No Picnic Global warming could take a heavy toll on city dwellers vulnerable to extreme heat.
While summer heat affects us all, extreme heat is a particular concern in big cities, where buildings, pavement, and other infrastructure absorb and radiate heat (the urban “heat island” effect). The result can be dangerously hot conditions—especially risky for the elderly, infants, the poor, and other vulnerable populations. If global warming emissions continue unabated, a number of large northeastern cities could experience triple the number of days over 90 °F by mid-century. In the latter part of the century, most of these cities could experience more than 60 days per year with temperatures topping 90 °F, and some could experience as many as 80 days. With lower emissions, roughly half this increase is expected. As for the very hottest days, most major Northeast cities currently endure, at most, a couple of 100 °F days in the average summer. With higher emissions, Philadelphia could experience up to 28 days above 100 ºF by the end of the century. Even Buffalo, NY, could experience 14 such days. With lower emissions, on the other hand, these cities would experience around six days per year at these dangerously hot temperatures. In light of the fact that 25 percent of the region’s population resides in major urban areas, the importance of reducing global warming emissions is clear.

Scorching Summers

Summertime in the Northeast is characterized by warm, often humid days, punctuated by occasional sweltering heat waves. But temperatures are on the rise, and the region faces dramatic increases in summer heat this century (see the sidebar “Summer in the City: No Picnic”) depending on the choices we make. If we stay on a higher-emission pathway we can expect distinctly hotter summer temperatures—between 4 and 8 ºF warmer by mid-century, and between 6 and nearly 14 °F warmer toward the end of the century. These increases are roughly double the change projected for a lower-emission pathway.

Compounding the problem is humidity, as warm air can hold more moisture. When rising humidity is factored in, summer days in some states under a higher-emission scenario may feel as much as 20 °F warmer than today—on par with the current climate of the southeastern United States (see migrating climate map).

Meeting the Challenge

The higher-emission pathway explored here is by no means a ceiling; emissions could conceivably go even higher, driving even more dangerous climate change. But the lower-emission pathway is also not a floor; with strong, near-term action to reduce emissions we could further curtail the magnitude and effect of projected climate change.

A Message That Hits Home Emphasizing the regional consequences of global warming can motivate local policy makers.
The findings of the October 2006 NECIA report Climate Change in the U.S. Northeast have not only received the attention of the region’s media but its policy makers as well. As Franz Litz, climate change policy coordinator for the state of New York, states, “Preserving the character of our communities will require significant reductions in heat-trapping emissions. The NECIA report is now an essential part of our climate change message to New Yorkers.” Gina McCarthy, Connecticut’s commissioner of environmental protection, has also found the report to be a useful outreach tool. “The NECIA,” she says, “with its visually compelling and accessible presentation of the critical [climate findings], has helped create a vivid picture of what global warming means to the people, character, and future of Connecticut.” To download the full report (in PDF format) visit the Union of Concerned Scientists’ Climate Choices website (www.climatechoices.org/ne). Or, order a printed copy for $12 by calling UCS at (617)547-5552.

Scientists have determined that we can achieve an even lower-emission pathway than the one described here if the United States and other industrialized countries reduce emissions to roughly 20 percent of their current level by mid-century, and developing countries follow a relatively low-emission pathway. To achieve cuts of this magnitude we must begin today.

The Northeast, as a global leader in technology, policy, finance, and innovation as well as a major source of carbon dioxide emissions (its energy-related emissions in 2001 were surpassed by only six nations), can set a leadership example in emission reduction. In fact, the Northeast has already taken a significant first step in the form of its Regional Greenhouse Gas Initiative (RGGI), the first multi-state cap on U.S. power plant emissions. And nearly all the states in the region have adopted California’s stringent emission standards for vehicles.

Encouragingly, more decision makers appear to be listening to the science, understanding the implications, and readying for action than in years past (see the sidebar “A Message that Hits Home”). The new Congress is considering federal climate legislation, and a growing number of U.S. corporations have expressed support for national emission standards.

The very character of the Northeast is at stake. Though the NECIA findings are sobering, they also present us with a question that can offer hope: which climate future are we, over the next few years, prepared to create? The choice is ours.

Erika Spanger-Siegfried, Northeast climate project manager, wrote this article based on the work of several NECIA authors.

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