Observed Impacts Of Global Climate Change

Contact: Justin Kenney, 215.575.4816, Katie Mandes, 703.516.0606


Arlington, VA - 11/09/2004 - Over the past century, Earth’s average temperature has increased by approximately 1 degree Farenheit. There is now strong evidence that this global warming is largely due to human emissions of greenhouse gases from a growing fossil fuel economy. Unless these emissions are checked, additional warming of 2 to 10 degrees is projected by the end of the 21st century. There are abundant signs, however, that the warming has already been sufficient to induce significant changes in the ecosystems and wildlife of the United States. A new report by the Pew Center on Global Climate Change, "Observed Impacts of Global Climate Change in the U.S.," by Camille Parmesan of The University of Texas at Austin and Hector Galbraith of Galbraith Environmental Sciences and the University of Colorado-Boulder, reviews the broad range of ecological changes that have occurred in response to human induced changes in the global and U.S. climate.

"U.S. ecosystems and wildlife are already responding to the warming climate," said Eileen Claussen, President of the Pew Center on Global Climate Change. "And this is only the beginning. With warming for the next century projected to be two to ten times greater than the last, we’re heading toward a fundamental and potentially irreversible disruption of the U.S. landscape and wildlife."

Numerous changes have already been observed and these changes have a range of implications for the United States, its ecosystems, and biodiversity. The responses of plants and animals to a changing climate are indicative of their natural ability to adapt, yet future global warming is likely to exceed the ability of many species to migrate or adjust. Furthermore, one species’ success in coping with climate change may be another species’ failure. The red fox, for example, is expanding into the range of the arctic fox, forcing the arctic fox into an ever-contracting area.

Other observed changes include a long-term trend toward an earlier spring, with earlier flowering and reproduction of plant and bird species. Butterflies on the U.S. west coast are moving north and to higher altitudes in search of tolerable climate conditions, with some populations disappearing altogether from the southern end of their ranges. And perhaps most alarming -- the frozen Arctic tundra is thawing, releasing carbon dioxide to the atmosphere in a feedback loop that could ultimately accelerate global warming.

In addition, wildlife attempting to cope with current global warming must also contend with myriad other challenges such as habitat fragmentation, invasive species, water diversion, environmental contamination, and over-exploitation, all of which collectively undermine their ability to adapt.

"What’s happening to our environment is not natural – it’s a problem of our own making. The longer we delay in reducing greenhouse gas emissions the greater the problem will become," said the Pew Center’s Claussen.

The report also highlights actions that can be taken to better manage U.S. natural resources to minimize the effects of climate change.

Pew is no longer active in this line of work, but for more information, visit the Center for Climate and Energy Solutions site.

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