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Today’s release of a widely anticipated international report on global warming coincides with a growing clamor within the United States to reduce greenhouse gas emissions and prevent the potentially devastating consequences of global climate change.

“There’s more interest in this now than at any time in the last 20 years,” says Ronald Prinn, TEPCO Professor of Atmospheric Sciences at MIT, who was a lead author of the report issued by the Intergovernmental Panel on Climate Change (IPCC).

The report issued today in Paris, a 21-page summary of a much longer study on the science behind climate change, concludes there is a greater than 90 percent chance that greenhouse gases from human activity are responsible for most of the steadily rising average global temperatures observed in the past 50 years.

“There’s clear evidence that greenhouse gases have been increasing by very large amounts since preindustrial times, and the vast majority of these increases are due to human activity,” said Prinn, whose specific task on the panel was to assess this issue.

This is the fourth climate report issued by the IPCC since it was established by the U.N. in 1988. Prinn, who is the director of MIT’s Center for Global Change Science, was one of more than 100 lead authors for the three-year study, which involved climate researchers from around the world.

For the first time, the IPCC provides extensive evidence of the regional signals of climate change, including rising continental-scale temperatures, rising sea levels, shrinking of Arctic summer sea ice and decrease in snow cover in the Northern Hemisphere. It also offers predictions for how rising temperatures will affect the planet in decades to come.

Taken as a whole, the report presents a strong case that the United States, which is responsible for about 25 percent of global greenhouse gas emissions, should take much more vigorous steps to curb its emissions along with the other major emitters around the world, Prinn said.

“Overall, the scientific evidence for human influence on climate has strengthened significantly in the past half dozen years, and the case for decreasing greenhouse gas emissions is significantly more compelling than it was six years ago,” he said.

Greenhouse gases, which include methane, nitrous oxide, ozone, chlorofluorocarbons and their replacements (hydrofluorocarbons) as well as the better-known carbon dioxide, trap infrared radiation in the Earth’s atmosphere, inhibiting the planet’s cooling capability. Burning of fossil fuels is a major contributor to greenhouse gas emissions, but agricultural activities and deforestation also contribute.

“It’s not just the highly industrialized nations that are involved here,” Prinn said. “To some degree, every person on the planet is responsible, but some are much more responsible than others.”

There is now a near-universal scientific consensus that human activity is driving climate change, but 10 years ago, Prinn himself was not convinced that that was the case. But, as the evidence mounted, Prinn concluded that the changes were too great to be explained by natural climate variations.

Filed under: Nature, World by lrenz