Tuesday, March 27, 2012

More on the Difficulties of Attributing Extreme Events

And here are more important points on extreme events, from a recent article in EOS by John M. Wallace:
Claims that the severity of heat waves, droughts, floods, and storms is increasing dramatically in response to global warming should, in fact, be viewed with caution for the following reasons:
  • The subtle early warning signs of global warming are beginning to be detectable in the statistics of extreme events such as droughts and episodes of heavy rainfall averaged over intervals of a few decades, but the changes reported thus far do not qualify as “dramatic” [Easterling et al., 2000; Intergovernmental Panel on Climate Change (IPCC), 2007].
  • The attribution of individual events—such as the current droughts in the Horn of Africa and Texas, the floods in Pakistan and Thailand, or the 2009 summer heat wave in Russia—to global warming is problematic because extreme events would occur from time to time even in an unchanging climate.
  • Even in the presence of climate change,extreme events do not occur often enough to enable scientists to track decade-to-decade changes in their statistics in real time, as they successfully do with more aggregated quantities such as global mean temperature and sea level [Palmer and Räisänen, 2002].
Via Dot Earth

1 comment:

charlesH said...

Reportedly, even the IPCC doesn't believe there is any evidence for co2 causing extreme events.

AGW scientific theory doesn't support it and the data doesn't either.

"The full IPCC Special Report on Extremes is out today, and I have just gone through the sections in Chapter 4 that deal with disasters and climate change. Kudos to the IPCC -- they have gotten the issue just about right, where "right" means that the report accurately reflects the academic literature on this topic. Over time good science will win out over the rest -- sometimes it just takes a little while."


A few quotable quotes from the report (from Chapter 4):

"There is medium evidence and high agreement that long-term trends in normalized losses have not been attributed to natural or anthropogenic climate change"

"The statement about the absence of trends in impacts attributable to natural or anthropogenic climate change holds for tropical and extratropical storms and tornados"

"The absence of an attributable climate change signal in losses also holds for flood losses"