Converging Weather Patterns Caused Last Winter’s Huge Snows
A Warming World Can Still See Severe Storms
That’s the headline on the news release from the Earth Institute at Columbia University for a new GRL study, “Northern Hemisphere winter snow anomalies: ENSO, NAO
and the winter of 2009/10″ (PDF here).
The study itself slams the “deniers” for trying to spin the storms as inconsistent with human-caused global warming:
The wintry winter has encouraged deniers of global warming, and those opposed to restrictions on greenhouse gas emissions, to mock climate change science. While these attacks confuse climate and weather and take a very geographically limited view (for example much of the Pacific Northwest had below normal snowfall), it is worth examining the causes for the winter’s snowfall anomalies. Such knowledge can be useful in climate prediction. In addition, explanations for climate and weather events that are in the news can help educate the public and diminish the effectiveness of efforts to exploit events to undermine the credibility of the science of climate change.
The abstract states, “the negative NAO [North Atlantic Oscillation] and El Ni±o event were responsible for the northern hemisphere snow anomalies of winter 2009/10.”
This might be true — though I think “primarily responsible” would be more defensible. And indeed the conclusion asserts, “We conclude that the anomalously high levels of snow in the mid”Atlantic states of the U.S. and in northwest Europe this past winter were forced primarily by the negative NAO and to a lesser extent by the El Ni±o.”
But one study is not dispositive in science and as is annoyingly typical of many of these kind of narrow studies, they simply don’t cite the full scientific literature. The GRL study looked at data from 1950 on.
But there was a 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.
Now the authors of the GRL may disagree with this, but to not even cite the paper seems a glaring omission — I guess that’s why it remains a little-known, scientific fact.
The authors also don’t cite the U.S. Global Change Research Program (USGCRP) U.S. Climate Impacts Report from 2009, which reviewed the 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]
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 Ni±o 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]
The GRL authors don’t cite a single one of those papers, which again seems somewhat of a glaring omission.
No, all these omissions don’t mean the GRL conclusion is wrong, but since they didn’t cite and challenge the conclusions of these other papers, it can’t be said that the GRL study refutes them or even disputes them.
Then we have this apparently as yet unpublished research presented by Dr James Overland of the NOAA/Pacific Marine Environmental Laboratory at the recent International Polar Year Oslo Science Conference (IPY-OSC) where he was chairing “a session on polar climate feedbacks, amplification and teleconnections, including impacts on mid-latitudes.”
“Cold and snowy winters will be the rule, rather than the exception,” says Dr James Overland….
Continued rapid loss of sea ice will be an important driver of major change in the world’s climate system in the years to come….
“While the emerging impact of greenhouse gases is an important factor in the changing Arctic, what was not fully recognised until now is that a combination of an unusual warm period due to natural variability, loss of sea ice reflectivity, ocean heat storage and changing wind patterns working together has disrupted the memory and stability of the Arctic climate system, resulting in greater ice loss than earlier climate models predicted,” says Dr Overland.
“The exceptional cold and snowy winter of 2009-2010 in Europe, eastern Asia and eastern North America is connected to unique physical processes in the Arctic,” he says.
Now that is an a strong and remarkable claim. If Overland is saying that the sharp drop in summer sea ice in recent years affects the autumn and winter Arctic weather in a unique way, then it may mean that studies that are largely based on data from before, say, 2005 — like the GRL study — are somewhat moot or at least open to reinterpretation.
I have queried Overland about this and will report back if he responds.
This is clearly a complicated, multivariate, and rapidly changing field of study. In response to the absurd claims of the disinformers and the credulous media coverage of those claims that the first Snowpocalypse was evidence against climate change science, I had written “Since one typically can’t make a direct association between any individual weather event and global warming, perhaps the best approach is to borrow and modify a term from the scientific literature and call this a “global-warming-type” deluge “” see Must-have PPT: The “global-change-type drought” and the future of extreme weather.”
Even though these storms occurred during warmest winter on record, I think the best way to talk about it until Overland publishes his work is the way NCAR’s Kevin Trenberth did on NPR (audio here):
RENEE MONTAGNE, host: With snow blanketing much of the country, the topic of global warming has become the butt of jokes. Climate skeptics built an igloo in Washington, D.C. during last weeks storm and dedicated it to former Vice President Al Gore, who’s become the public face of climate change. There was also a YouTube video called “12 Inches of Global Warming” that showed snowplows driving through a blizzard.For scientists who study the climate, it’s all a bit much. As NPRs Christopher Joyce reports, they’re trying to dig out.
CHRISTOPHER JOYCE: Snowed-in Washington is where much of the political debate over climate change happens. So it did not go unnoticed when a Washington think-tank that advocates climate action had to postpone a climate meeting last week because of inclement weather.
That kind of irony isnt lost on climate scientists. Most don’t see a contradiction between a warming world and lots of snow. Heres Kevin Trenberth, a prominent climate scientist at the National Center for Atmospheric Research in Colorado.
Mr. KEVIN TRENBERTH (Scientist, National Center for Atmospheric Research): The fact that the oceans are warmer now than they were, say, 30 years ago, means there’s about, on average, 4 percent more water vapor lurking around over the oceans than there was, say, in the 1970s.
JOYCE: Warmer water means more water vapor rises up into the air. And what goes up, must come down.
Mr. TRENBERTH: So one of the consequences of a warming ocean near a coastline like the East Coast and Washington, D.C., for instance, is that you can get dumped on with more snow, partly as a consequence of global warming.
JOYCE: And Trenberth notes that you don’t need very cold temperatures to get big snow. In fact, when the mercury drops too low, it may be too cold to snow.
There’s something else fiddling with the weather this year: a strong El Nino. That’s the weather pattern that, every few years, raises itself up out of the western Pacific Ocean and blows east to the Americas. It brings heavy rains and storms to California and the South and Southeast. It also pushes high-altitude jet streams farther south, which brings colder air with them.
Trenberth also says El Nino can lock in weather patterns like a meteorological highway, so that storms keep coming down the same track. True, those storms have been big ones – record breakers. But meteorologist Jeff Masters, with the Web site Weather Underground, says it’s average temperatures “” not snowfall “” that really measure climate change.
There’s more water vapor lurking around the oceans, and whatever the proximate cause of any one snow storm, there is little doubt that global warming means the overwhelming majority of East Coast storms will be sweeping in more moisture and dumping it on the ground.
For more on Trenberth’s analysis, see Exclusive interview: NCAR’s Trenberth on the link between global warming and extreme deluges.