Recent Declines in Northern Hemisphere Winter Daily Temperature Variability

Monday, 15 December 2014
Zeke Hausfather, Steven Mosher and Robert A Rohde, Berkeley Earth, Berkeley, CA, United States
There is considerable uncertainty regarding the expected change in short-term temperature variability in a warming world. As the earth warms, local weather may become more variable, less variable, or stay about the same. Daily surface station temperature data compiled by Berkeley Earth spanning the period from 1960 to present is used to examine spatial trends in short-term varaibility by decomposing station data into a longer-term trend, an average seasonal cycle, changes over time in the seasonal cycle, and residual variability. We find statistically significant declines in Nothern Hemisphere winter maximum temperature variability, with much of the observed decline concentrated in the past 15 years in high-latitude areas. Fall variability has also declined over the period examined, but these declines appear to be more modest. Spring and summer variability have no identifiable significant trends globally, though there are a few areas with notable increases. For the most part, weather variability appears to have changed little due to recent warming, with the likely exception of decreased variability in regions and months where snow accumulation is plausible. Potential correlations with changes in snow cover and sea ice extent are examined, and the implications of potential inhomogenities in the source data are explored.