[I]t is imperative that the Committee have an understanding of the science of climate change…The potential implications of these results are illustrated by multiple recent weather disasters.
So says Rep. Henry Waxman in urging the House Energy and Commerce Committee to hold yet another hearing on climate science before introducing bipartisan legislation to block EPA’s far-reaching carbon restrictions. Waxman’s so-called smoking gun is two studies published in Nature last month—here and here—which hold that climate change “may be responsible for the increases in heavy precipitation that have been observed over much of the Northern Hemisphere…over the past several decades.”
Waxman would have you believe this is settled science, what he and his colleagues refer to as “mounting scientific evidence linking strange and dangerous weather to rising carbon levels in the atmosphere.”
My words of advice for Rep. Waxman and his cronies on demands for the science hearing: Be careful what you wish for.
The hearing is likely to reveal what Andrew Revkin of the New York Times concludes: the Nature paper is not definitive at all.”
Revkin—hardly known for being a climate change skeptic—writes in two lengthy blog posts—here and here—that not withstanding scientists’ and reporters’ sensationalized summaries and “oversimplifications” of the studies, there are “uncertainties related to observational limitations, missing or uncertain external forcing and model performance.”
Revkin also reminds his readers that extreme weather is nothing new and has occurred “going back several millenniums.” He links to a 2002 New York Times article he wrote which is worth a read given the present debate:
Four times since the last ice age, at intervals roughly 3,000 years apart, the Northeast has been struck by cycles of storms far more powerful than any in recent times, according to a new study. The region appears to have entered a fifth era in which such superstorms are more likely, the researchers say.
… the work illustrates that natural extremes of weather — what one researcher, Paul R. Bierman, a geologist at the University of Vermont, called a ”drumbeat of storminess” — are many times greater than those experienced in the modern era.
The clues from the lakes appear to mesh with evidence of other periods of stormy weather around the North Atlantic, including variations in traces of salt from sea spray locked in layers of Greenland glaciers, the authors said. They also appear synchronized with the occasional cold snaps in Europe that sent glaciers grinding forward down alpine valleys, the study says.
The similar storm rhythms seen around the North Atlantic may mean that the overall pattern is driven by slow cycles in a pole-girdling wind and pressure pattern called the Arctic oscillation, which in turn could be caused by cycles of solar activity, they said.
The lake records from the Northeast show that the region had much stormier eras that peaked 11,900, 9,100, 5,800 and 2,600 years ago. Then, about 600 years ago, another period of storminess appeared to begin and has been ”ramping back up again,” Dr. Bierman said.
The current trend is so prolonged and diffuse that the century-plus history of recorded weather data is not long enough to pick up a pattern. But it is etched quite clearly in the lake beds, said another author, Eric J. Steig, a climatologist at the University of Washington.
The scientists checked to see whether influences other than big storms might have made the surrounding earth more apt to crumble. They considered forest fires, but found no evidence of raised concentrations of charcoal in the lake bottom.
The likeliest source of each layer is an intense burst of precipitation, perhaps on already soggy soil, over just a day or two, the researchers said. Given the much greater thickness of many of the ancient layers compared with those left by floods like the 1927 disaster in Vermont, they said, society should at least ponder the potential for much greater catastrophes.
In an interview, the researchers emphasized that there was no way to quantify how severe the flooding might be, but they said rainfall could reach several inches an hour — easily enough to cause massive landslides, particularly if the soil was already soggy.
”This shows that in human experience, at least historical human experience, we don’t know what this climate system is capable of,” Dr. Steig said.
While revealing the rising potential for epic storms, the new findings are likely to confound efforts to discern whether human alterations of the atmosphere, particularly a buildup of heat-trapping greenhouse gases, are increasing the frequency of severe downpours, as many climate experts have predicted.
But the research could indicate that engineers and planners, when considering the design of public works like bridges and reservoirs, should take into account the possibility of extremely rare, but extremely destructive, floods, said the study’s lead author, Anders J. Noren, formerly of the University of Vermont and now at the Limnological Research Center of the University of Minnesota.
”If this cycle continues,” Mr. Noren said, ”the frequency and severity of intense rainstorms that can cause massive flooding should continue to increase for the next several hundred years.”
But Revkins’ recent blog are all about his distaste for what he calls the “inadequate accountability in the news business for oversimplications that overplay the front-page thought” on climate change:
… this does raise big questions about the standards scientists and journals use in summarizing complex work and the justifiable need for journalists — and readers — to explore such work as if it has a “handle with care” sign attached.
In the policy arena, the eagerness to trim away caveats is even more pronounced, as was the case when climate treaty negotiators in Cancún erroneously oversimplified the core finding of the 2007 report from the Intergovernmental Panel on Climate Change. In that instance, the error was fixed.
If this scientific “evidence” is the best that Rep. Waxman can muster linking global warming with severe weather, let the hearing begin.