Wrong Again: UK Climate Scientist Debunks Obama’s Science Advisor On Climate Change

  • Date: 17/06/14
  • Lewis Page, The Register

A top British expert has come out with new research flatly contradicting the idea that extremely cold winters in North America – like the one just past – will become more frequent due to global warming. This new analysis disagrees completely with the assessment of President Obama’s science advisor.

Dr James Screen of Exeter uni in England is a mathematician who has been studying the arctic ice sheet for several years. According to a university announcement highlighting his latest research:

Climate change is unlikely to lead to more days of extreme cold, similar to those that gripped the USA in a deep freeze last winter … [Recent changes in the Arctic climate have] actually reduced the risk of cold extremes across large swathes of the Northern Hemisphere.

Screen’s new paper is published in the hefty climate journal Nature Climate Change. In it he writes:

Subseasonal cold-season temperature variability has significantly decreased over the mid- to high-latitude Northern Hemisphere in recent decades. This is partly because northerly winds and associated cold days are warming more rapidly than southerly winds and warm days … decreases in subseasonal cold-season temperature variability … are detectable in the observational record and are highly robust in twenty-first-century climate model simulations.

Or, in other words, severe cold spells like the ones Americans and Canadians have just suffered through are not increasing in frequency and shouldn’t be expected to.

That contradicts very sharply with the view of Dr John Holdren, president Obama’s White House science and technology adviser. He says:

“A growing body of evidence suggests that the kind of extreme cold experienced by the United States is a pattern we can expect to see with increasing frequency as global warming continues.”

 

White House video, 8 January 2014: President Obama’s Science and Technology Advisor, Dr. John Holdren, explains the polar vortex in 2 minutes—and why climate change makes extreme weather more likely going forward.

Full story

Arctic amplification decreases temperature variance in northern mid- to high-latitudes

James A Screen

Nature Climate Change, 15 June 2014 

Changes in climate variability are arguably more important for society and ecosystems than changes in mean climate, especially if they translate into altered extremes (1, 2, 3). There is a common perception and growing concern that human-induced climate change will lead to more volatile and extreme weather (4). Certain types of extreme weather have increased in frequency and/or severity (5, 6, 7), in part because of a shift in mean climate but also because of changing variability (1, 2, 3, 8, 9, 10). In spite of mean climate warming, an ostensibly large number of high-impact cold extremes have occurred in the Northern Hemisphere mid-latitudes over the past decade (11). One explanation is that Arctic amplification—the greater warming of the Arctic compared with lower latitudes (12) associated with diminishing sea ice and snow cover—is altering the polar jet stream and increasing temperature variability (13, 14, 15, 16). This study shows, however, that subseasonal cold-season temperature variability has significantly decreased over the mid- to high-latitude Northern Hemisphere in recent decades. This is partly because northerly winds and associated cold days are warming more rapidly than southerly winds and warm days, and so Arctic amplification acts to reduce subseasonal temperature variance. Previous hypotheses linking Arctic amplification to increased weather extremes invoke dynamical changes in atmospheric circulation (11, 13, 14, 15, 16), which are hard to detect in present observations (17, 18) and highly uncertain in the future (19, 20). In contrast, decreases in subseasonal cold-season temperature variability, in accordance with the mechanism proposed here, are detectable in the observational record and are highly robust in twenty-first-century climate model simulations.