The catastrophic destruction that has occurred in the central Gulf coast of the United States due to Hurricane Katrina is occupying our thoughts. This calamity will consume enormous time and cost to recover from and to provide as much protection as possible from the inevitable next hurricane of this magnitude in this region and elsewhere. This is a sad time.
However, little time has passed before the disaster is being blamed by some of the media on global warming (see, for example, articles in The Belfast Telegraph and the Los Angeles Times. This narrow perspective completely misses the real reason for this disaster. As we, and others, have discussed (see Pielke, R.A. Sr., 2000: Discussion Forum: A broader perspective on climate change is needed and Pielke Jr. et al. 2005: Hurricanes and global warming), the significant risks are due to crossing thresholds in our vulnerability to environmental threats of all types. In this case, construction of towns on the immediate coastline and of a city below sea level (New Orleans) makes these regions particularly vulnerable to hurricanes. In the book,
the exposure of the coastal population to hurricanes in the eastern United States is clear (see Figure 2.8 (d) on page 52), with New Orleans clearly at risk. What this figure also shows is that other urban areas along the Gulf and Atlantic coasts have also become increasingly vulnerable as population grows, and, therefore, infrastructure development accelerates.
Even with respect to global warming, its reasons for occurring over the past several decades, while predominately due to humans (see our Climate Science post of August 29th), is not predominately due to the increase in the atmospheric concentrations of carbon dioxide, nor is global warming the more significant way humans are altering the climate system (see our Climate Science post of July28th What is the Importance to Climate of Heterogeneous Spatial Trends in Tropospheric Temperatures?). The media have almost universally ignored an accurate description of the spectrum of human forcings on climate as presented in the National Research Council 2005 report.
Thus the advocates of blaming global warming erroneously assume that carbon dioxide emissions are the main cause of this disaster, but miss the other human caused global warming forcings that we summarized in our August 29th blog. They miss that other climate change effects, both due to natural and human- caused influences, such as atmospheric and ocean circulation changes due to spatially heterogeneous climate forcings such as landscape changes and aerosol emissions, have a greater effect than the relatively small magnitude of global warming that has actually been documented (see Pielke and Christy 2005)
The media fail to recognize that climate is complex and involves numerous natural and human climate forcings and feedbacks. To focus on the radiative warming forcing of carbon dioxide shows a complete misunderstanding of the climate system. We recommend they read the 2005 National Research Council report . They also need to understand that we cannot rely on even the complete description of climate change to understand our vulnerability to hurricanes and other weather events. We need to focus on an integrated assessment of the vulnerability of specific societal and environmental resources, (such as an urban center) to the entire spectrum of risks (see Table E.7 in Pielke, R.A. Sr., and L. Bravo de Guenni, 2004, for a summary of the vulnerability perspective as contrasted with using climate models to define risk).
Thus the answer to the question posed in this blog, is that we cannot attribute this disaster to global warming, or even climate change. It is a human-caused disaster resulting from decisions made as to where to locate our population and commerce, without enough protection to avoid inevitable catastrophic consequences.