This is one of the reasons severe weather has been on the decrease. Less variance means less mixing, and mixing of extreme temperature differential air masses is what contributes to volatile weather events like tornado outbreaks.
Here is the paper:
Arctic amplification decreases temperature variance in northern mid- to high-latitudes
James A. Screen Nature Climate Change (2014) doi:10.1038/nclimate2268
Changes in climate variability are arguably more important for society and ecosystems than changes in mean climate, especially if they translate into altered extremes1, 2, 3. There is a common perception and growing concern that human-induced climate change will lead to more volatile and extreme weather4. Certain types of extreme weather have increased in frequency and/or severity5, 6, 7, in part because of a shift in mean climate but also because of changing variability1, 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 decade11.
One explanation is that Arctic amplification—the greater warming of the Arctic compared with lower latitudes12 associated with diminishing sea ice and snow cover—is altering the polar jet stream and increasing temperature variability13, 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 circulation11, 13, 14, 15, 16, which are hard to detect in present observations17, 18 and highly uncertain in the future19, 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.
A non-paywalled presentation of the results is here: http://www.cesm.ucar.edu/working_groups/Polar/presentations/2014/screen.pdf
Zeke Hausfather notes:
Part of a growing consensus that a warmer world would, on balance, have less variance in temperature, particulary high-latitude areas. I wrote a bit about it here: http://www.yaleclimatemediaforum.org/2014/06/more-temperature-variability-in-a-warming-world-not-so/