Scientists have been predicting for decades that increased greenhouse gas emissions would lead to an increase in many kinds of extreme weather events, especially more intense precipitation and more brutual heat waves. So it’s not a big shock that what is likely to be the hottest year on record has witnessed so many blow-out extreme weather events from Nashville to Moscow to Pakistan — see NASA’s Hansen: Would recent extreme “events have occurred if atmospheric carbon dioxide had remained at its pre-industrial level of 280 ppm?” The “appropriate answer” is “almost certainly not.” Indeed, “The first nine months of the year have seen the highest number of weather-related events since Munich Re started keeping records,” according to Dr. Peter Hoeppe, Head of the Geo Risks Research Department at Munich Re. He said “that a clear pattern of continuing global warming was contributing to the natural disasters.”
Recently, some December precipitation records have been falling — in Seattle and Portland, Oregon. These weren’t the 1000-year extremes that I typically write about — or the statistical aggregation of U.S. record highs vs. record lows — but I merely point them out because the anti-science crowd, led by discredited former TV weatherman Anthony Watts, persists in shouting about precipitation primarily when it comes down in solid form, even when it isn’t record-breaking. Snowstorms are pretty much all the disinformers have left to shout about now, at least to those who don’t pay close attention to the science.
Since we’re entering the snowy season and can expect a blizzard of disinformation in this area, I’m updating this post from February, “We get more snow storms in warm years!”
Everybody talks about the weather, but few read the scientific literature about it.
The anti-science crowd has been doing a killer job pushing the myth that the big recent snowstorms somehow undercut our understanding of human-caused global warming. But aside from the fact the precipitation isn’t temperature, it turns out that the “common wisdom” the disinformers are preying on — lots of snow means we must be in a cold season — isn’t even true.
Let’s look at the results of an actual, detailed study of “the relationships of the storm frequencies to seasonal temperature and precipitation conditions” for the years “1901–2000 using data from 1222 stations across the United States.” The 2006 study, “Temporal and Spatial Characteristics of Snowstorms in the Contiguous United States“ (Changnon, Changnon, and Karl [of National Climatic Data Center], 2006) found we are seeing more northern snow storms and that we get more snow storms in warmer years:
The temporal distribution of snowstorms exhibited wide fluctuations during 1901–2000, with downward 100-yr trends in the lower Midwest, South, and West Coast. Upward trends occurred in the upper Midwest, East, and Northeast, and the national trend for 1901–2000 was upward, corresponding to trends in strong cyclonic activity…..
Results for the November–December period showed that most of the United States had experienced 61%– 80% of the storms in warmer-than-normal years. Assessment of the January–February temperature conditions again showed that most of the United States had 71%–80% of their snowstorms in warmer-than-normal years. In the March–April season 61%–80% of all snowstorms in the central and southern United States had occurred in warmer-than-normal years…. Thus, these comparative results reveal that a future with wetter and warmer winters, which is one outcome expected (National Assessment Synthesis Team 2001), will bring more snowstorms than in 1901–2000. Agee (1991) found that long-term warming trends in the United States were associated with increasing cyclonic activity in North America, further indicating that a warmer future climate will generate more winter storms.
This year, of course, is poised to be the hottest year on record, so big snowstorms wouldn’t be terribly surprising, at least for those who follow the scientific literature.
The U.S. Global Change Research Program (USGCRP) U.S. Climate Impacts Report from 2009 reviewed that literature and concluded:
Cold-season storm tracks are shifting northward and the strongest storms are likely to become stronger and more frequent. Large-scale storm systems are the dominant weather phenomenon during the cold season in the United States. Although the analysis of these storms is complicated by a relatively short length of most observational records and by the highly variable nature of strong storms, some clear patterns have emerged.112 [Kunkel et al., 2008]
Storm tracks have shifted northward over the last 50 years as evidenced by a decrease in the frequency of storms in mid-latitude areas of the Northern Hemisphere, while high-latitude activity has increased. There is also evidence of an increase in the intensity of storms in both the mid- and high-latitude areas of the Northern Hemisphere, with greater confidence in the increases occurring in high latitudes.112 [Kunkel et al., 2008] The northward shift is projected to continue, and strong cold season storms are likely to become stronger and more frequent, with greater wind speeds and more extreme wave heights.68 [Gutowski et al, 2008]
Snowstorms The northward shift in storm tracks is reflected in regional changes in the frequency of snowstorms. The South and lower Midwest saw reduced snowstorm frequency during the last century. In contrast, the Northeast and upper Midwest saw increases in snowstorms, although considerable decade-to-decade variations were present in all regions, influenced, for example, by the frequency of El Niño events.112 [Kunkel et al., 2008]
There is also evidence of an increase in lake-effect snowfall along and near the southern and eastern shores of the Great Lakes since 1950.97 [Cook et al, 2008] Lake-effect snow is produced by the strong flow of cold air across large areas of relatively warmer ice-free water. As the climate has warmed, ice coverage on the Great Lakes has fallen. The maximum seasonal coverage of Great Lakes ice decreased at a rate of 8.4 percent per decade from 1973 through 2008, amounting to a roughly 30 percent decrease in ice coverage (see Midwest region). This has created conditions conducive to greater evaporation of moisture and thus heavier snowstorms. Among recent extreme lake-effect snow events was a February 2007 10-day storm total of over 10 feet of snow in western New York state. Climate models suggest that lake-effect snowfalls are likely to increase over the next few decades.130 [Burnett et al., 2003] In the longer term, lake-effect snows are likely to decrease as temperatures continue to rise, with the precipitation then falling as rain.129 [Kunkel et al, 2002].
Finally, the words of Dr. Kevin Trenberth, head of the Climate Analysis Section at the National Center for Atmospheric Research, in the NY Times this August bear repeating:
“It’s not the right question to ask if this storm or that storm is due to global warming, or is it natural variability. Nowadays, there’s always an element of both.”
