Oct 7, 2007

New Evidence on Future Climate Variability

Increasing Variability in a Warmer World? The Abstract did not challenge that, the contents did!


Changes in variability and persistence of climate in Switzerland: Exploring 20th century observations and 21st century simulations

Abstract
This paper investigates the shift in variance under conditions of atmospheric warming, under the paradigm that a warmer climate induces greater variability, as has been suggested by a number of other studies. Based upon observational data since 1900 at both a low and a high elevation site in Switzerland it is shown that, at least for these locations, the inter-annual and decadal variability of both maximum and minimum daily temperatures has in fact decreased over the course of the 20th century despite the strong warming that has been observed in the intervening period. The decrease in climate variability is attributed to changes in daily weather conditions as well as these aggregated in weather types, with an observed reduction in the more perturbed weather types and an increase in the weather patterns that exhibit greater persistence, particularly since the 1960s and 1970s. The greater persistence recorded in daily weather conditions associated with more elevated pressure fields helps to explain the decrease in variability during a period where minimum and maximum temperatures have been observed to rise considerably since 1900. An insight into the future behavior of temperature variability in Switzerland, based on the daily results of a regional climate model applied to the IPCC A-2 emissions scenario (a high greenhouse-gas emissions scenario leading to strong climate forcing during the 21st century) suggests that a warmer climate may induce greater variability in maximum temperatures, but also greater persistence beyond selected thresholds; in the case of minimum temperatures, variance remains close to current conditions in the latter part of the 21st century, but the persistence of cold events diminishes substantially, as can be expected in a climate that is estimated by the climate model to warm by about 4°C on average in Switzerland.
Source:
www.sciencedirect.com
Global and Planetary Change, Volume 57, Issues 1-2, May 2007, Page vii
Martin Beniston and St├ęphane Goyett.

So this is what the abstract says. You wouldn't probably expect a copy of an intro for a climate change related paper on this blog, which looks into future climate variability in Switzerland, given the scenario of an increase in temperature of 4°C towards the end of the 21st century. In the recent post consensus and sea ice record tandem, a consensus of >0.4°C could be deducted throughout the 21st century, if the current trend of human induced increase in global mean surface temperature continues. Looking from the corner of one's eye at Oreskes' claim that non of the abstracts of a sample of hundreds of peer-reviewed papers challenge the consensus on global warming, one could shrug and say. OK - another paper that does not challenge the consensus position.

Now this is what Beniston and Goyette, 2007, found out:

The team collected daily maximum and minimum temperature records from a low elevation station station (Basel, 300 meters above sea level, my home town) and a high elevation station (Saentis, 2500 meters above seal) from 1901 to 2004. These stations were selected based on their quality, representativeness, and completeness. For each year, they calculated the mean and variance of the daily maximum and minimum temperatures, and they converted the mean and variance values into anomalies based on a 1961-1990 "normal" 30-year period.

They demonstrated that the temperatures at both sites have increased by approximately 2°C over the most recent four decades. However, here comes the surprise. The authors note that whatever the period considered, the variance decreases with increasing temperature. Let's say it again: So the minimum temperatures were less extreme, but the maximum temperatures were also less extreme.

This is contrary to to horror scenarios which suggest that the weather will be more violent with rising temperatures, right? This is why the contrarian 'World Climate Report' picked it up from the newly published science book Global and Planetary Change and posted itand posted it here

2 comments:

Climate Patrol said...

UPDATE CLIMATE VARIABILITY IN A WARMING WORLD? DOOMSDAY CALLED OFF - AGAIN!!CO2Science.orghas just posted "Climate Variability in a Warming World", describing the wheather record in Basel, my home town in Switzerland, exactly as I have recorded it during Average temperatures went up by 2 C, but the possibility of extreme temperatures stays the same. The record temperature of 39.2 C in 1983 was btw never topped off, not even during the extreme summer 2003!!

Climate Patrol said...

UPDATE CLIMATE VARIABILITY IN A WARMING WORLD? DOOMSDAY CALLED OFF - AGAIN!! CO2Science.org has just posted "Climate Variability in a Warming World", describing the wheather record in Basel, my home town in Switzerland, exactly as I have noticed during my lifetime. Average temperatures went up by 2 C while the possibility of extreme temperatures stays the same. The record temperature of 39.2 C in 1983 was btw never topped off, not even during the extreme summer 2003!!