Tuesday, December 20, 2016

Categorical Evidence of Climate Change

A new study published in Nature Geoscience present retreating glaciers as categorical evidence of climate change.
Using only meteorological and glacier observations, and the characteristic decadal response time of glaciers, we demonstrate that observed retreats of individual glaciers represent some of the highest signal-to-noise ratios of climate change yet documented. Therefore, in many places, the centennial-scale retreat of the local glaciers does indeed constitute categorical evidence of climate change.
Discussion can be found here and here.
Using records of glacier length that go back over 400 years, the researchers show that shrinking of mountain glaciers in five continents could almost certainly not have happened if the Earth wasn’t warming up.
Here is an interactive map.
Using the long-term records, the researchers estimated how glacier lengths have varied in response to the yearly ups and downs of temperature and snowfall. They then compared these natural fluctuations with the large-scale retreat seen in the glaciers in the 20th and 21st centuries.

Their findings show there’s only a very small chance that the retreat of these glaciers could have happened without climate change, says lead author Prof Gerard Roe from the Earth and Space Sciences department at the University of Washington. He tells Carbon Brief:
“Our paper demonstrates that the worldwide retreat of glaciers necessarily requires a climate change that is centennial in duration and global in extent.”

The findings constitute “categorical evidence” that the climate is warming, the paper says.
The evidence for climate change is usually presented by climate scientists in basic results from which the consequences often must be inferred.  But now there can be no disqualification by climate change deniers. The climate change deniers can retreat in cherry picked data in defiance of the overwhelming overall evidence, but now, more and more evidence that can't be overlooked is being presented.

 It is happening and we have to do something about it now.