Linking Weather and Climate | Nature
Is human-influenced climate change contributing to extreme weather? The much-discussed link between climate and weather adds complicated emotions to already heart-wrenching scenes of flooding and drought. There is a sense of foreboding, of weather patterns predicted to become more frequent. For those living high-carbon lifestyles (most people in, say, North America), there may also be a sense of culpability, acknowledged or not. (See: "The Ethics of Climate Change.")
But links between weather and climate are also controversial. As recently as September 2010, the NYT's Andrew Revkin insisted: "While some may be tempted to label this summer’s extremes the manifestation of our climate meddling, there’s just not a clear-cut link – yet."
Now, two links are claimed, in a pair of Nature articles. From the report by Quirin Schiermeier (sub. req.):
[T]wo studies in this week's Nature conclude that climate warming is already causing extreme weather events that affect the lives of millions. The research directly links rising greenhouse-gas levels with the growing intensity of rain and snow in the Northern Hemisphere, and the increased risk of flooding in the United Kingdom.
At the RealClimate blog, Gavin Schmidt explains:
The aim of the Pall et al paper was to examine a specific event – floods in the UK in Oct/Nov 2000. Normally, with a single event there isn’t enough information to do any attribution, but Pall et al set up a very large ensemble of runs starting from roughly the same initial conditions to see how often the flooding event occurred. ... The results gave varying numbers but in nine out of ten cases the chance increased by more than 20%, and in two out of three cases by more than 90%. ... One neat and interesting feature of these experiments was that they used the climateprediction.net set up to harness the power of the public’s idle screensaver time.
The second paper (Min et al.) is a more standard detection and attribution study. By looking at the signatures of climate change in precipitation intensity and comparing that to the internal variability and the observation, the researchers conclude that the probability of intense precipitation on any given day has increased by 7 percent over the last 50 years – well outside the bounds of natural variability.
Schmidt also stresses four points for understanding the links between extreme weather and climate:
- Not all extremes are the same.
- There is no theory or result that indicates that climate change increases extremes in general.
- Some extremes will become more common in future (and some less so).
- Attribution of extremes is hard.