Global Science Report is a feature from the Center for the Study of Science, where we highlight one or two important new items in the scientific literature or the popular media. For broader and more technical perspectives, consult our “Current Wisdom.”
A story this week that has been making the rounds in the climate-media complex finds that natural variability is responsible for perhaps as much as 50% of the summertime decrease in Arctic sea ice that has taken place over the past 30 years or so (anthropogenic climate change is the presumed factor in the remainder).
This isn’t new. The last (2013) science report from the UN’s Intergovernmental panel on climate change said:
Using climate model simulations from the NCAR CCSM4…inferred that approximately half (56%) of the observed rate of decline from 19979 to 2005 was externally (anthropogenically) forced, with the other half associated with natural internal variability.
Ten years ago, a study was conducted by a team led by Julienne Stroeve that looked at the observed rate of Arctic sea ice loss and compared it to climate model expectations. [A side note here: the loss of Arctic sea ice (which is floating ice) does not lead to sea level rise just as the melting of ice in your cocktail doesn’t lead to your glass overflowing]. What Stroeve and colleagues found was the Arctic sea ice was being lost at a far brisker pace than climate models had predicted (Figure 1).