Just weeks after one group of scientists officially announced the end of global warming, the so-called hiatus, another group reacted by claiming that there has never been a pause in global warming. Instead, there has been a global misperception that warming slowed between 1998 and 2012, but only because of data gaps, particularly in the Arctic, the fastest warming region on the planet. "We recalculated global average temperatures from 1998 to 2012 and found that the rate of global warming continued to increase at 0.112°C per decade instead of slowing to 0.05°C per decade as previously thought," said Xiangdong Zhang International Arctic Research Center at the University of Alaska, Fairbanks. He and colleagues say in the journal Nature Climate Change that their new estimates suggest the Arctic has warmed by more than six times the global average in the first decades of this century.
The argument about the apparent slowdown in the rate of global warming - that warming has slowed but not stopped - provides a case study of science in action. Many theories from the mid-1980s to the end of the century, atmospheric carbon dioxide levels of greenhouse gases continued to rise as economies expanded, energy demand increased, and people burned more and more coal, oil, and natural gas. Global temperatures have also risen, according to greenhouse gas reports. Then, after the hottest year ever in 1998, a year in which a natural cyclical climate phenomenon called El Niño drove temperatures even hotter - the rate of warming seemed to get worse, even as carbon dioxide rates continued to rise.
In Asia, Europe and America, researchers have gone back to the drawing board. Some groups blamed shifts in a natural cycle of ocean warming and cooling, some blamed volcanic eruptions that may have thinned solar radiation, and some blamed changes in trade winds. Others disputed the conclusion: perhaps the so-called slowdown was a matter of perspective. Perhaps the rise in extreme temperatures over the past decade and a half has distorted the data set. And even if the slowdown in the rate of increase of global warming was indeed real, it had no bearing on long-term projections. So the latest study may not be the last word on the subject.
"We recalculated global average temperatures from 1998 to 2012 and found that the rate of global warming continued to increase at 0.112°C per decade, instead of slowing to 0.05°C per decade as previously thought"
There is now no doubt that warming has resumed at a predictable rate and that each of the last three years 2014-16 has been the hottest on record, and 2017 could be listed as one of the three hottest. And the continuing warming of the world would have been more clearly recorded if Arctic instruments had been more complete. To recalculate, the Fairbanks team used temperature data from the University of Washington's international Arctic Buoy program and newly corrected sea surface temperatures from the U.S. government's National Oceanic and Atmospheric Administration. Until recent years, researchers had not believed changes in the Arctic - and in November 2016 Arctic temperatures were 20°C above normal for the time of year - would be large enough to influence global average temperatures. "The Arctic is remote only in terms of physical distance," Professor Zhang said. "From a scientific point of view, it is close to each of us. It is a necessary part of the equation and the answer affects us all. " - source Climate News Network
