Evidence of man-made global warming is "the gold standard": scientists

OSLO (Reuters) – Evidence of global warming by humans has reached a level of certainty "to the norm", adding additional pressure for a reduction in greenhouse gases to limit rising temperatures , scientists said Monday.

"Humanity can not afford to ignore such clear signals," the US-led team writes in Nature Climate Change on satellite measurements of rising temperatures over the past 40 years years.

They claimed that the assurance that human activities increased heat on the Earth's surface had reached the "five sigma" level, a statistical gauge indicating that there was only a one in a million chance that a signal would appear if there was no warming.

Such a "gold standard" was applied in 2012, for example, to confirm the discovery of the subatomic particle of the Higgs boson, a basic building block of the universe.

Benjamin Santer, lead author of the Monday study at the Lawrence Livermore National Laboratory in California, said he hoped the results would win the skeptics and spur action.

"It is wrong to say that scientists do not know that the cause of climate change is bad," he told Reuters. "We do."

The mainstream scientists claim that burning fossil fuels causes more floods, droughts, heat waves and sea level rise.

US President Donald Trump has often questioned global warming and plans to pull out of the 197-nation Paris climate agreement, which aims to end the century's era of fossil fuels. moving to cleaner energies such as wind and solar energy.

Sixty-two percent of Americans polled in 2018 believed that climate change had a human cause, compared to 47% in 2013, according to the Yale Climate Change Communication Program.

SATELLITE DATA

Researchers in the United States, Canada and Scotland on Monday said evidence of global warming had reached the five-sigma level by 2005 in two of the three sets of satellite data widely used by researchers and 2016 in the third.

Professor John Christy, from the University of Alabama at Huntsville, who manages the third dataset, said there were still many gaps in the understanding of climate change. His data show a slower warming than the other two series.

"You can see a certain fingerprint that indicates a human influence, but that the actual intensity of the influence is minor (as indicated by our satellite data)," he said. Reuters.

In addition, in 2013, the United Nations Intergovernmental Panel on Climate Change (IPCC) concluded that it is "extremely likely", or at least 95% likely, that human activities are the primary cause of change. since the 1950s.

Peter Stott, of the UK Met Office, who was among the scientists who drew this conclusion and who did not participate in Monday's study, said he would favor increasing the likelihood of a noticeable at 99-100%.

"The alternative explanation of the dominant natural factors is even less likely," he told Reuters.

The last four years have been the warmest since records began in the 19th century.

The IPCC will then publish a formal assessment of probabilities in 2021.

"I would be reluctant to bring it up to 99-100%, but there is no question that there is more evidence of a change in global signals compared to a broader set of. oceanic and atmospheric indices, "said Professor Nathan Bindoff, climate scientist at University of Tasmania.