U.S. Report Says Humans Cause Climate Change
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The Climate Science Special Report, unveiled by 13 federal agencies, is an exhaustive scientific report that says humans are the dominant cause of the global temperature rise that has created the warmest period in the history of civilization. Over the past 115 years global average temperatures have increased 1.8 degrees Fahrenheit, leading to record-breaking weather events and temperature extremes, the report says. The global, long-term warming trend is “unambiguous,” it says, and there is “no convincing alternative explanation” that anything other than humans — the cars we drive, the power plants we operate, the forests we destroy — are to blame.
The climate science report is part of a congressionally mandated review conducted every four years known as the National Climate Assessment. The product of hundreds of experts within the government and academia and peer-reviewed by the National Academy of Sciences, it is considered the United States’ most definitive statement on climate change science.
“The climate has changed and is always changing,” Raj Shah, a White House spokesman, said in the statement. “As the Climate Science Special Report states, the magnitude of future climate change depends significantly on ‘remaining uncertainty in the sensitivity of Earth’s climate’” to greenhouse gas emissions, he added.
“This new report simply confirms what we already knew. Human-caused climate change isn’t just a theory, it’s reality,” said Michael E. Mann, a professor of atmospheric science at Pennsylvania State University. “Whether we’re talking about unprecedented heat waves, increasingly destructive hurricanes, epic drought and inundation of our coastal cities, the impacts of climate change are no longer subtle. They are upon us. That’s the consensus of our best scientists, as laid bare by this latest report.”
The report says the Earth has set temperature highs for three years running, and six of the last 17 years are the warmest years on record for the globe. Weather catastrophes from floods to hurricanes to heat waves have cost the United States $1.1 trillion since 1980, and the report warns that such phenomena may become common.
“The frequency and intensity of extreme high temperature events are virtually certain to increase in the future as global temperature increases,” the report notes. “Extreme precipitation events will very likely continue to increase in frequency and intensity throughout most of the world.”
In the United States, the report finds that every part of the country has been touched by warming, from droughts in the Southeast to flooding in the Midwest to a worrying rise in air and ground temperatures in Alaska, and conditions will continue to worsen.
“This assessment concludes, based on extensive evidence, that it is extremely likely that human activities, especially emissions of greenhouse gases, are the dominant cause of the observed warming since the mid-20th century,” the report states. “For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence.”