About Science and Impacts

The Earth’s average surface temperature has increased by 1.4°F (0.8°C) since the early years of the 20th century. The 11 warmest years on record (since 1850) have all occurred in the past 13 years. The five warmest years to date are 2005, 1998, 2002, 2003, 2007.

The scientific consensus is that global warming is largely the result of increased atmospheric concentrations of carbon dioxide and other greenhouse gas emissions. The growth in emissions is caused by human activities, primarily fossil fuel combustion and changes in land use, such as agriculture and deforestation. The Intergovernmental Panel on Climate Change projects an increase of future average global surface temperature in the range of 2.0°F to 11.5°F (1.1°C to 6.4°C) by 2100, with warming in the United States expected to be about 50 percent greater. This warming, along with the associated changes in precipitation, drought, heat waves, and sea-level rise, will have important consequences for the U.S. environment and economy. Globally, climate change presents many challenges, particularly in poorer countries far less able to cope with a changing climate and in low-lying countries where sea level rise will cause severe damage to society and ecosystems.

The Pew Center's Science and Impacts Program educates the public and policymakers about the climate system and the environmental and economic implications of climate change for the United States, including impacts on natural ecosystems and resources, social systems, human health, and infrastructure. The Pew Center publishes a series of peer-reviewed scientific reports written by experts on the environmental impacts of climate change. Workshops sponsored by the Pew Center explore the implications of environmental impacts for climate change policy. The Pew Center constantly builds relationships with members of the scientific, policy, and business community to increase awareness regarding the science and impacts of climate change.