When it comes to extreme weather, climate activists want to have their cake and eat it. Many acknowledge that it is unscientific to attribute any particular weather event to global warming. But then, in the same breath, they’ll say that this or that drought, flood, or hurricane is “consistent with” the types of weather “scientists” predict will become more frequent in a warming world.
Or they’ll say that such weather is “exactly what global warming looks like.” Or they’ll say that because “all weather events are affected by a warming planet,” the burden of proof is now on skeptics to show that climate change did not cause or contribute to a particular weather-related disaster.
Some activists, though, simply come right out and assert what others insinuate. Plaintiffs in Comer v. Murphy Oil, a case that made it all the way to a federal appeals court, claimed that carbon dioxide (CO2) emissions from ExxonMobil, American Electric Power, and other U.S. energy and power companies contributed to global warming, which intensified Hurricane Katrina, which in turn wrought death and destruction upon the citizens of New Orleans.
There was a major “anthropogenic” component to the New Orleans disaster — but it was not the emissions. Decade after decade, policymakers failed to improve a levee system “predicted to fail in a major hurricane,” as Cato Institute climatologist Patrick Michaels noted at the time.
Although always a staple of global warming advocacy, climate activists have turned up the rhetorical heat on extreme weather in recent years. The reasons aren’t hard to fathom. The 15-year pause in global warming makes it harder to scare people about warming itself. The two greatest terrors featured in An Inconvenient Truth — rapid ice sheet disintegration leading to catastrophic sea-level rise and ocean circulation shutdown precipitating a new ice age — have no credibility. Nobody takes seriously the prospect of warming-induced malaria epidemics either. If you want to scare people, extreme weather is the only card left in the climate alarm deck.
In addition, a rationally-ignorant public can easily be fooled into confusing climate change risk with plain old climate risk (the nasty surprises Mother Nature generates all on her own). Part of the reason is psychological. Due to their sheer magnitude and terror, natural catastrophes have an almost supernatural aspect. People are naturally inclined to imagine that natural disasters have non-natural causes. Thus, each time disaster strikes, pundits, especially those with scientific credentials, can plausibly blame fossil fuels — just as in earlier ages political or religious authorities blamed “sinners” (i.e., their adversaries) for floods, plagues, crop failures, and the like.
Perhaps the leading debunker of extreme-weather hype on the scene today is University of Colorado Prof. Roger Pielke, Jr., who testified last week before the Senate Environment and Public Works Committee at a hearing titled “Climate Change: It’s Happening Now.”
As his testimony notes, Pielke, Jr. is not a climate change skeptic. He affirms, for example, that “Humans influence the climate system in profound ways, including through the emission of carbon dioxide via the combustion of fossil fuels.” However, he regards the oft-asserted linkage between global warming and recent hurricanes, floods, tornadoes, and drought as “unsupportable based on research and evidence.” Highlights of his testimony appear below.
Globally, weather-related losses have not increased since 1990 as a proportion of GDP (they have actually decreased by about 25%).
Source of loss data: Munich Re. Source of GDP data, UN.
Insured catastrophe losses have not increased as a proportion of GDP since 1960.
Source: Aon Benfield
Hurricanes have not increased in the US in frequency since at least 1900.
The red line shows the linear trend, exhibiting a decrease from about 2 to 1.5 landfalls per year since 1900. Source: NOAA
Hurricanes have not increased in the US in intensity since at least 1900.
The heavy black line shows the linear trend. Source NOAA, figure courtesy Chris Landsea, NOAA/NHC.
Hurricane damages in the US (adjusted for changes in population, wealth, and consumer price index) have not changed since at least 1900.
The figure includes Superstorm Sandy (2012) in gray and placeholders for the three other post-tropical cyclones of hurricanes which made landfall in 1904, 1924 and 1925. Source: Pielke, Jr et al. 2008 as updated to 2012 using ICAT Damage Estimator.
There is no significant trend (up or down) in global tropical cyclone landfalls since 1970 (when data allows for a comprehensive perspective).
Source: Weinkle et al. 2012
There are no significant trends in global tropical hurricane frequency or accumulated cyclone energy since 1970.
Total count of tropical cyclones of tropical storm (top curve) and hurricane strength, 12-month running sums 1970 through June 30, 2013. Figure courtesy Ryan Maue.
Floods have not increased in the US in frequency or intensity since at least 1950.
Percent of US streamguages above “bankfull streamflow” defined as the highest daily mean streamflow value expected to occur, on average, once in every 2.3 years. Source: USGS
Flood losses as a percentage of US GDP have dropped by about 75% since 1940.
Annual flood losses have decreased from about 0.2% of US GDP to <0.05% since 1940. Flood loss data from NOAA Hydrologic Information Center.
Tornadoes have not increased in frequency, intensity, or normalized damage since 1950, and there is some evidence to suggest they have actually declined.
Annual number of tornadoes 1954-2012. Source: NOAA
Annual number of strong tornadoes 1954-2012. Source: NOAA
Estimated total damage if tornadoes of past years occurred with 2012 levels of development, updating Simmons et al. 2012.
Droughts have “for the most part, become shorter, less frequent, and cover a smaller portion of the U. S. over the last century.”
The quote comes from U.S. Climate Change Research Program 2008 report on extreme weather. The figure shows the area in severe to extreme drought as measured by the Palmer Drought Severity Index for the United States (red) from 1900 to present and for North America (blue) from 1950 to present.
A final observation. Pielke, Jr. acknowledges that considerable research “projects” various weather extremes to become more frequent or intense in the future as a consequence of anthropogenic climate change. However, even if those projections prove correct, “it will be many decades, perhaps longer, before the signal of human-caused climate change can be detected in the statistics of hurricanes (and to the extent that statistical properties are similar, in floods, tornadoes, drought).”
Heat waves are becoming more frequent, as Pielke, Jr. acknowledged in Q&A. Indeed, it would be surprising if heat waves were not more common during the past three decades than in the 1950s-1970s. Does this mean we are in the midst of a “planetary emergency”? No.
Last summer, NASA scientist James Hansen published an op-ed in the Washington Post titled “Climate change is here – and worse than we thought.” His thesis: The worst hot spells of the past decade were “a consequence of climate change” and have “virtually no explanation other than climate change.” However, expert assessments of the European heat wave of 2003, the Russian heat wave of 2010, the Texas-Oklahoma drought of 2011, and the Midwest drought of 2012 concluded that each event was chiefly due to natural variability, not anthropogenic climate change.
Moreover, of all the weather extremes popularly attributed to climate change, heat waves allow for the most rapid and effective adaptation. Davis et al. (2003) found that as summer air temperatures increased (whether due to the expansion of urban heat islands, global warming, or both), U.S. heat-related mortality declined. U.S. cities with the most frequent hot weather, such as Tampa, Florida and Phoenix, Arizona, have the lowest heat-related mortality.
Average heat-related mortality in U.S. urban areas has declined nationwide; subsequent research shows this trend continues into the 21st century. [Sources: Davis RE, et al., 2003. Changing Heat-Related Mortality in the United States. Environmental Health Perspectives 111, 1712–18. Kalkstein, L.S., et al., 2011. An evaluation of the progress in reducing heat-related human mortality in major U.S. cities. Natural Hazards 56, 113-129.]
From all which I conclude that although climate change may be “happening now,” we are not in the midst of a climate “crisis.”
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