Evidence for man-made global warming hits 'gold standard' according to scientists.
Evidence for man-made global warming has reached a "gold standard" level of certainty, with scientists urging cuts in greenhouse gases to limit rising temperatures.
Evidence for man-made global warming has reached a "gold standard" level of certainty, adding pressure for cuts in greenhouse gases to limit rising temperatures, scientists said on Monday.
"Humanity cannot afford to ignore such clear signals," the US-led team wrote in the journal Nature Climate Change of satellite measurements of rising temperatures over the past 40 years.
They said confidence that human activities were raising the heat at the Earth's surface had reached a "five-sigma" level, a statistical gauge meaning there is only a one-in-a-million chance that the signal would appear if there was no warming.
Such a "gold standard" was applied in 2012, for instance, to confirm the discovery of the Higgs boson subatomic particle, a basic building block of the universe.
Benjamin Santer, lead author of Monday's study at the Lawrence Livermore National Laboratory in California, said he hoped the findings would win over sceptics and spur action.
"The narrative out there that scientists don't know the cause of climate change is wrong," he told Reuters. "We do."
Mainstream scientists say the burning of fossil fuels is causing more floods, droughts, heat waves and rising sea levels.
US President Donald Trump has often cast doubt on global warming and plans to pull out of the 197-nation Paris climate agreement which seeks to end the fossil fuel era this century by shifting to cleaner energies such as wind and solar power.
Sixty-two percent of Americans polled in 2018 believed that climate change has a human cause, up from 47 percent in 2013, according to the Yale Program on Climate Change Communication.
Monday's findings, by researchers in the United States, Canada and Scotland, said evidence for global warming reached the five sigma level by 2005 in two of three sets of satellite data widely used by researchers, and in 2016 in the third.
Professor John Christy, of the University of Alabama in Huntsville which runs the third set of data, said there were still many gaps in understanding climate change. His data show a slower pace of warming than the other two sets.
"You may see a certain fingerprint that indicates human influence, but that the actual intensity of the influence is minor (as our satellite data indicate)," he told Reuters.
Separately in 2013, the United Nations' Intergovernmental Panel on Climate Change (IPCC) concluded that it is "extremely likely", or at least 95 percent probable, that human activities have been the main cause of climate change since the 1950s.
26 February 2019