European Hotties
A Report Produced by The CO2 & Climate Team
A Service of The Greening Earth Society
3/15/2004Whether the summer of 2003 was the hottest on record in Western Europe or wasn’t, we may never know. But the high temperatures should not have taken Europeans by surprise.
Original research on seasonal temperature changes appears in the March 5, 2004 edition of Science. After reconstructing Western Europe’s seasonal temperature history since 1500, a team of Swiss climate scientists concludes summer 2003 was the warmest since the beginning of their reconstruction. The second-warmest was about 250 years ago, in 1757.
As warm as 2003 was, probable errors in the early records should have led Jurg Lauterbacher and his team to a much softer conclusion about whether it was the all-time warmest. Peer-reviewers at Science appear reluctant to temper a potential contributor’s overly strong statements about climate change.
Figure 1 depicts reconstructed European summer temperatures since 1500 based upon thermometer records and temperature proxies. Thermometer records are increasingly sparse as the record marches back in time. There are none before 1659. As a consequence, “proxy records” (e.g. tree rings data) are critical to the integrity of the early part of this temperature reconstruction and usually only can capture between a quarter and half of the true inter-summer temperature change. This potentially results in large errors.
Lauterbacher et al. note the potential for error, but don’t emphasize the uncertainty proxy records impose. The uncertainty is so great that it is critical to determining whether one summer (like that of 2003) is in fact hotter than any other in their record.
Figure 1. Reconstructed European summer (June, July, August) temperature history since 1500 (from Luterbacher et al., 2004).
Notice how the Swiss record is characterized by large year-to-year variations (black line) over a slowly varying 30-year average (red line). The blue lines represent the ninety-five percent confidence range for these three-decadal weighted averages. The blue lines do not represent the error expected in a given year. As we will explain, these confidence ranges call into question the team’s conclusions about 2003.
The history of summer temperature varies a great deal on decade-to-century scales. There was a rapid rise in average summer temperature in the early- to mid-18th century. This made many summers in the latter part of the 18th century and early portion of the 19th century warmer than recent ones (with the exception of 2003). A nearly two-century-long cooling trend set in after that. As a consequence summers in the early part of the 20th century were the coldest in 500 years. During the last hundred years, temperatures have recovered from their nadir in 1902.
While it is safe to say summer 2003 was very warm, how does it compare with that of 1757? If the thirty-year period encompassing that summer actually was near the top of the confidence limit (upper blue line), then 2003 and 1757 are indistinguishable.
Why didn’t the researchers provide error bars for individual years? If climatologists on staff at World Climate Alert had been among the peers reviewing this paper, we would have advised Science to insist on such a calculation. We may be on to something here!
Those blue lines are derived from thirty-year weighted averages. In three consecutive centuries (1500 to 1800), the upper (or warmest) confidence limit exceeds the confidence limit at any time in the 20th century. That makes the estimation of the true value of a given year in the first three hundred years of this record problematic, to say the least. A statement that 2003 is warmer than any other year is rendered the product of a little creative (and perhaps wishful) thinking. This kind of speculation should have been excised during the peer review process.
But that’s a quibble. Summer 2003 was hot. And as we said at the top, Europeans should have seen it coming. Average summer temperatures have been on the rise for three decades. It was only a matter of time before natural variation led to an anomalously warm summer superimposed on the already warmer climate of the late 20th and early 21st centuries.
Euro-summer 2003 became particularly newsworthy when the number of heat-related deaths soared alongside temperature. In regions where extreme heat is rare, significantly elevated heat wave mortality results.
Heat waves become increasingly common in a warming climate. They also become more frequent as cities warm under an “urban heat island” effect. Take Chicago, by way of example.
During a July 1995 heat wave, it is reported there were more than 700 excess heat-related deaths in Chicago. In July 1999, a heat wave of nearly identical character resulted a few more than 100 excess deaths. What made the difference? Adaptation.
In only four years, Chicago’s residents have learned how better to deal with extreme heat. The steps they took reduced mortality by 86 percent. In 1999, the National Weather Service in Chicago issued heat wave warnings well in advance. Press releases reminded everyone of the 1995 death toll. “Cooling centers” were opened throughout the city and made accessible via free bus service. Municipal workers and police officers checked on elderly residents. Such simple measures — adaptations over a short period of time — literally saved hundreds of lives (Palecki et al., 2001). Western Europeans now have an opportunity and motivation to similarly adapt.
Let’s grant that Europe was caught off guard by 2003’s heat, much the way Chicago was in 1995. Given dismissal of many governmental officials because of their lack of preparedness last time, we can bet that next time around things will be different. Can they be? Of course. As W.R Keatinge, in a 2000 article in the British Medical Journal, writes:Populations in Europe have adjusted successfully to mean summer temperatures ranging from 13.5°C to 24.1°C and can be expected to adjust to global warming predicted for the next half-century with little sustained increase in heat-related mortality. Active measures to accelerate adjustment to hot weather could minimize temporary rise in heat related mortality, and measures to maintain protection against cold in winter could permit substantial reductions in overall mortality as temperatures rise.
Chicago’s adaptations to a warming climate can be accomplished by Europeans. Adaptation seems more efficacious than the trying to change the climate’s course. Chicago’s 1995 heat wave killed several thousand fewer people than died in France in 2003. Availability of air-conditioning powered by relatively inexpensive electricity has something to do with it. Both commodities (low-priced electricity and air-conditioning) are more cost-prohibitive under Europe’s energy and climate policies, however.
References
Keatinge, W.R., et al., 2000. Heat related mortality in warm and cold regions of Europe: observational study. British Medical Journal, 321, 670–673.Luterbacher, J., et al., 2004. European seasonal and annual temperature variability, trends, and extremes since 1500, Science, 303, 1499–1503.
Palecki, M.A., S.A. Changnon, and K.E. Kunkel, 2001. The nature and impacts of the July 1999 heat wave in the midwestern United States: Learning from the lessons of 1995, Bulletin of the American Meteorological Society, 82, 1353–1367.
