Climate in crisis
WASHINGTON The rapid pace of global climate change is almost certainly driven by human activity, like burning fossil fuels, according to a United States government report that contradicts assertions by US President Donald Trump and members of his administration.
‘‘For the warming over the last century, there is no convincing alternative explanation supported by the extent of the observational evidence,’’ says the report by a group of more than 50 US government scientists, released yesterday.
The report, which is required by Congress every four years, was written by scientists from government bodies such as the Environmental Protection Agency (EPA) and the National Oceanic and Atmospheric Administration (NOAA).
It reinforces the conclusions drawn by an overwhelming majority of scientists around the world in recent years that emissions from burning fossil fuels are the primary driver of global warming, leading to sea level rise, flooding, droughts, and more frequent powerful storms.
Trump has repeatedly called climate change a hoax, and in June he announced that he would withdraw the US from a global pact to combat it, calling the deal’s demands for emissions cuts too costly for his country’s economy. War-torn Syria is the only other country outside the pact.
The US withdrawal from the Paris Climate Deal was part of a broader White House effort to roll back what it sees as unneeded environmental protections to boost domestic oil and gas drilling and coal mining.
EPA Administrator Scott Pruitt has also expressed doubts about the causes of climate change, at one point saying he did not believe carbon dioxide from human activity was the primary driver, and calling for further debate on the issue.
White House spokesman Raj Shah said: ‘‘The administration supports rigorous scientific analysis and debate and encourages public comment on the draft documents being released today.’’
Officials at the EPA declined to comment.
According to the report, global temperatures have increased by about 1 degree C over the last 115 years, while global average sea levels have risen about 17.78cm over the same period.
Sea levels were expected to rise ‘‘at least several inches in the next 15 years’’ due to rising temperatures, it added. Heatwaves, downpours and wildfires have become more frequent.
Despite fears by some scientists, David Fahey of the NOAA and several authors said there was no political interference or censoring of the 477-page report.
‘‘A lot of what we’ve been learning over the last four years suggests the possibility that things may have been more serious than we think,’’ said Robert Kopp of Rutgers University, one of dozens of scientists inside and outside the government who contributed to the report.
It was ‘‘extremely likely’’ – meaning with 95 to 100 per cent certainty – that global warming was man-made, mostly from the spewing of carbon dioxide into the atmosphere from the burning of coal, oil and natural gas, the scientists concluded.
The scientists calculated that the human contribution to warming since 1950 had been between 92 and 123 per cent. It was more than 100 per cent at one end, because some natural forces – such as volcanoes and the orbital cycle – were working to cool Earth, but they were being overwhelmed by the effects of greenhouse gases, said study co- author Katharine Hayhoe of Texas Tech.
‘‘This period is now the warmest in the history of modern civilisation,’’ she said.
For the first time, scientists highlighted a dozen ‘‘tipping points’’ of potential dangers that could happen from warming.
They include the slowing down of the giant Atlantic Ocean circulation system, which could dramatically warp weather worldwide; much stronger El Nino weather patterns; major decreases in ice sheets in Greenland and Antarctica, which would spike sea level rise; and massive release of methane and carbon dioxide from thawing permafrost, which could turbocharge warming.
The researchers did not provide an estimate of how likely tipping points would occur, but ‘‘there is certainly some chance of some of these things happening’’, Fahey said.
The report also documented how different climate changecaused events can interact in a complex way to make life worse, such as the California wildfires and Superstorm Sandy five years ago.
The world’s oceans were under a ‘‘triple threat’’ – the water was getting warmer and more acidic and seeing a drop in oxygen levels, Hayhoe said.
The scientists detailed dozens of ways global warming is already affecting parts of the US. They said changes to weather, food, air, water and diseases were sickening, injuring and killing Americans, and the situation was expected to get worse, hurting the economy, wildlife and energy supply. Reuters, AP