Friday, April 28, 2017

Scientists keep increasing their projections for how much the oceans will rise this century

[Spokesman Review] A report by a leading research body monitoring the Arctic has found that previous projections of global sea level rise for the end of the century could be too low, thanks in part to the pace of ice loss of Arctic glaciers and the vast ice sheet of Greenland.
It’s just the latest in a string of cases in which scientists have published numbers that suggest a grimmer picture than the one presented in 2013 by an influential United Nations body, the Intergovernmental Panel on Climate Change.
The new Snow, Water, Ice and Permafrost in the Arctic report presents minimum estimates for global sea level rise by the end of the century, but not a maximum. This reflects the fact that scientists keep uncovering new insights that force them to increase their sea level estimates further, said William Colgan, a glaciologist with the Geological Survey of Denmark and Greenland, who contributed to the sea level rise section.
“Because of emerging processes, especially related to the Greenland ice sheet and the Antarctic ice sheet, it now looks like the uncertainties are all biased positive,” Colgan said.
The assessment found that under a relatively moderate global warming scenario – one that slightly exceeds the temperature targets contained in the Paris climate agreement – seas could be expected to rise “at least” 52 centimeters, or 1.7 feet, by the year 2100. Under a more extreme, “business as usual” warming scenario, meanwhile, the minimum rise would be 74 centimeters, or 2.4 feet.
The new findings were published Tuesday as part of a broader overview report by the Arctic Monitoring and Assessment Program, a working group of the intergovernmental Arctic Council, which unites eight Arctic nations, including the United States, and six organizations representing the indigenous peoples of the Arctic.
It is the work of 90 scientists and 28 peer reviewers and is expected to be presented in Fairbanks, Alaska, next month at the next summit of Arctic political leaders.
The report bluntly contrasts its sea level findings with a previous 2013 report from the U.N. Intergovernmental Panel on Climate Change, which had put the “likely” low end sea level rise number for these two scenarios at 32 centimeters (about 1 foot) and 45 centimeters (1.5 feet) for the period between 2081 and 2100. That global body – whose high end sea level rise number for the year 2100 was just shy of one meter, or 3.2 feet – has often seen its assertions on sea level rise faulted by scientists for being too conservative. Read More