Scientists are now extremely confident that humans are responsible for the global warming seen in the past six decades, according to a new international study.
The Intergovernmental Panel on Climate Change on Friday said it was “extremely likely” that warming since the 1950s has been man-made, adopting its strongest language yet on the state of the world’s climate system.
In its previous assessment in 2007 the U.N. panel said it was “very likely” that humans caused global warming.
But in the new report, which was published in Stockholm and will be released in full on Monday, the IPCC left little doubt that greenhouse gas emissions from industrial activity, vehicles and other sources are causing a rapid rise in global temperatures.
“The atmosphere and ocean have warmed, the amount of snow and ice has diminished, the global mean sea level has risen and the concentrations of greenhouse gases have increased,” Qin Dahe, the co-chair of the IPCC working group that compiled the report, said in a statement.
The IPCC report projected a sea level rise by 2100 of 26-82 centimeters, up from the 18-59 centimeter rise it predicted six years ago.
The report also projected that average temperatures will rise 0.3 to 4.8 degrees C by the end of the century.
The projections were based on four emissions scenarios. Only two of them were below the 2 degree C benchmark that countries have set to avoid the worst impacts of climate change.
“This is yet another wakeup call,” United States Secretary of State John Kerry said in a statement. “Once again, the science grows clearer, the case grows more compelling, and the costs of inaction grow beyond anything that anyone with conscience or common sense should be willing to even contemplate.”
The report also addressed evidence that global warming has slowed since 1998, which climate deniers have used to argue that climate change isn’t man-made.
The IPCC said that a short-term variation in temperature doesn’t affect long-term climate trends. Most scientists believe that in the past 15 years heat has increasingly settled in the ocean, but that hypothesis wasn’t included in the report.
Governments use the report to help shape international climate treaties. A new agreement is supposed to be signed in 2015, but that is unlikely to happen as developing countries like China continue to spar with the United States and other industrialized nations over how to reduce global greenhouse gas emissions.
