Global warming is affecting where and how Americans live and work, and evidence is mounting that burning fossil fuels has made extreme weather such as heat waves and heavy precipitation much more likely in the USA, according to a massive federal report released Tuesday at the White House.
"Climate change is here and now, and not in some distant time or place," said Texas Tech University climate scientist Katharine Hayhoe, one of the authors of the 1,100-page National Climate Assessment (NCA), the largest, most comprehensive U.S.-focused climate change report ever produced.
"The choices we're making today will have a significant impact on our future," Hayhoe said.
The assessment was prepared by hundreds of the USA's top scientists. It agreed with a recent report by the United Nations Intergovernmental Panel on Climate Change that the planet is warming, mostly because of human activity.
The assessment provides "the loudest and clearest alarm bell to date" for immediate and aggressive climate action, said John P. Holdren, President Obama's science advisor, at a press conference in Washington today.
"All Americans will find things that matter to them in this report," added Jerry Melillo, chair of the National Climate Assessment Development Advisory Committee.
"Corn producers in Iowa, oyster growers in Washington State and maple syrup producers in Vermont are all observing climate-related changes that are outside of recent experience," the U.S. report stated. "So, too, are coastal planners in Florida, water managers in the arid Southwest, city dwellers from Phoenix to New York and native peoples on tribal lands from Louisiana to Alaska."
While scientists continue to refine projections of the future climate, observations unequivocally show that the climate is changing and that the warming of the past 50 years is primarily due to human-induced emissions of heat-trapping gases such as carbon dioxide and methane. These emissions come mainly from the burning of coal, oil and gas, the report states.
"If people took the time to read the report, they would see that it is not necessarily about polar bears, whales or butterflies," said meteorologist Marshall Shepherd of the University of Georgia. "I care about all of those, but the NCA is about our kids, dinner table issues, and our well being."
"We're already seeing extreme weather and it's happening now," said study co-author Donald Wuebbles, a climate scientist at the University of Illinois. "We're seeing more heat waves, particularly in the West and in the South."
Specifically, the three most significant threats from climate change in the USA are sea level rise along the coasts, droughts and fires in the Southwest and extreme precipitation events across the country.
The assessment was written by 300 scientists and other experts from academia; local, state and federal governments; the private sector; private citizens; and the non-profit sector. Representatives from oil companies such as ConocoPhillips and Chevron and environmental groups such as the Nature Conservancy endorsed the assessment's findings.
"The National Climate Assessment brings to light new and stronger evidence of how climate change is already having widespread impacts across the United States," according to Kevin Kennedy of the World Resources Institute, a Washington, D.C.- based environmental group.
"Chevron recognizes and shares the concerns of governments and the public about climate change," said Chevron spokesperson Justin Higgs. "Chevron's Arthur Lee was one of 60 committee members and 240 authors to assist in the compilation of this report. We recognize the importance of this issue and are committed to continued research and understanding."
A vast majority of climate scientists — generally pegged at 97% — concur with the basics of the science behind climate change, though some still find flaws in the details. A report last week, for instance, in the peer-reviewed journal Nature Climate Change found that the impacts of extreme heat are often exaggerated while the impacts of adaptation to the heat are underplayed.
The assessment is a federally mandated report prepared by the nation's top scientists every four years for the president and Congress to review. This is the third report produced.
The United States Global Change Research Program (USGCRP) coordinated the development of the NCA, which is exclusively focused on climate impacts to the United States, according to the requirements of the Global Change Research Act of 1990.
Contributing: Associated Press