Floods in Europe
From ClimateWiki
From Climate Change Reconsidered, a work of the Nongovernmental International Panel on Climate Change
In the midst of 2002’s massive flooding in Europe, Gallus Cadonau, the managing director of the Swiss Greina Foundation, called for a punitive tariff on U.S. imports to force cooperation on reducing greenhouse gas emissions, claiming that the flooding “definitely has to do with global warming” and stating that “we must change something now” (Hooper, 2002). Cadonau was joined in this sentiment by Germany’s environment minister, Jurgen Trittin, who implied much the same thing when he said “if we don’t want this development to get worse, then we must continue with the consistent reduction of environmentally harmful greenhouse gasses” (Ibid.).
The IPCC seems to agree with Cadonau and Trittin. Its authors report “a catastrophic flood occurred along several central European rivers in August 2002. The floods resulting from extraordinarily high precipitation were enhanced by the fact that the soils were completely saturated and the river water levels were already high because of previous rain. Hence, it was part of a pattern of weather over an extended period” (IPCC, 2007-I, p. 311). While admitting “there is no significant trend in flood occurrences of the Elbe within the last 500 years,” the IPCC nevertheless says the “observed increase in precipitation variability at a majority of German precipitation stations during the last century is indicative of an enhancement of the probability of both floods and droughts” (Ibid.)
Research
Nesje et al. (2001) analyzed a sediment core from a lake in southern Norway in an attempt to determine the frequency and magnitude of floods in that region. The last thousand years of the record revealed “a period of little flood activity around the Medieval period (AD 1000-1400),” which was followed by a period of extensive flood activity that was associated with the “post-Medieval climate deterioration characterized by lower air temperature, thicker and more long-lasting snow cover, and more frequent storms associated with the ‘Little Ice Age’.” This particular study suggests that the post-Little Ice Age warming the earth has experienced for the past century or two—and which could well continue for some time to come—should be leading this portion of the planet into a period of less-extensive floods.
Pirazzoli (2000) analyzed tide-gauge and meteorological data over the period 1951-1997 for the northern portion of the Atlantic coast of France, discovering that the number of atmospheric depressions and strong surge winds in this region “are becoming less frequent.” The data also revealed that “ongoing trends of climate variability show a decrease in the frequency and hence the gravity of coastal flooding,” which is what would be expected in view of the findings of Nesje et al.
Reynard et al. (2001) used a continuous flow simulation model to assess the impacts of potential climate and land use changes on flood regimes of the UK’s Thames and Severn Rivers; and, as might have been expected of a model study, it predicted modest increases in the magnitudes of 50-year floods on these rivers when the climate was forced to change as predicted for various global warming scenarios. However, when the modelers allowed forest cover to rise concomitantly, they found that this land use change “acts in the opposite direction to the climate changes and under some scenarios is large enough to fully compensate for the shifts due to climate.” As the air’s CO2 content continues to rise, there will be a natural impetus for forests to expand their ranges and grow in areas where grasses now dominate the landscape. If public policies cooperate, forests will indeed expand their presence on the river catchments in question and neutralize any predicted increases in flood activity in a future high-CO2 world.
Starkel (2002) reviewed what is known about the relationship between extreme weather events and the thermal climate of Europe during the Holocene. This review demonstrated that more extreme fluvial activity was typically associated with cooler time intervals. In recovering from one such period (the Younger Dryas), for example, temperatures in Germany and Switzerland rose by 3-5°C over several decades; “this fast shift,” in Starkel’s words, “caused a rapid expansion of forest communities, [a] rise in the upper treeline and higher density of vegetation cover,” which led to a “drastic” reduction in sediment delivery from slopes to river channels.
Mudelsee et al. (2003) analyzed historical documents from the eleventh century to 1850, plus subsequent water stage and daily runoff records from then until 2002, for two of the largest rivers in central Europe: the Elbe and Oder Rivers. The team of German scientists reported that “for the past 80 to 150 years”—which the IPCC claims was a period of unprecedented global warming—“we find a decrease in winter flood occurrence in both rivers, while summer floods show no trend, consistent with trends in extreme precipitation occurrence.” As the world has recovered from the global chill of the Little Ice Age, flooding of the Elbe and Oder rivers has not materially changed in summer and has actually decreased in winter. Blaming anthropogenic CO2 emissions for the European flooding of 2002, then, is not a reasoned deduction based on scientific evidence.
On September 8 and 9, 2002, extreme flooding of the Gardon River in southern France occurred as a result of half-a-year’s rainfall being received in approximately 20 hours. Floods claimed the lives of a number of people and caused much damage to towns and villages situated adjacent to its channel. The event elicited much coverage in the press; in the words of Sheffer et al. (2003), “this flood is now considered by the media and professionals to be ‘the largest flood on record’,” which record extends all the way back to 1890. Coincidently, Sheffer et al. were in the midst of a study of prior floods of the Gardon River, so they had data spanning a much longer time period. They report that “the extraordinary flood of September 2002 was not the largest by any means,” noting that “similar, and even larger floods have occurred several times in the recent past,” with three of the five greatest floods they had identified to that point in time occurring over the period AD 1400-1800 during the Little Ice Age. Commenting on these facts, Sheffer et al. stated that “using a longer time scale than human collective memory, paleoflood studies can put in perspective the occurrences of the extreme floods that hit Europe and other parts of the world during the summer of 2002.”
Lindstrom and Bergstrom (2004) analyzed runoff and flood data from more than 60 discharge stations scattered throughout Sweden, some of which provide information stretching to the early- to mid-1800s, when Sweden and the world were still experiencing the cold of the Little Ice Age. This analysis led them to discover that the last 20 years of the past century were indeed unusually wet, with a runoff anomaly of +8 percent compared with the century average. But they also found that “the runoff in the 1920s was comparable to that of the two latest decades,” and that “the few observation series available from the 1800s show that the runoff was even higher than recently.” What is more, they note that “flood peaks in old data are probably underestimated,” which “makes it difficult to conclude that there has really been a significant increase in average flood levels.” In addition, they say “no increased frequency of floods with a return period of 10 years or more, could be determined.”
With respect to the generality of their findings, Lindstrom and Bergstrom say that conditions in Sweden “are consistent with results reported from nearby countries: e.g. Forland et al. (2000), Bering Ovesen et al. (2000), Klavins et al. (2002) and Hyvarinen (2003),” and that, “in general, it has been difficult to show any convincing evidence of an increasing magnitude of floods (e.g. Roald, 1999) in the near region, as is the case in other parts of the world (e.g. Robson et al., 1998; Lins and Slack, 1999; Douglas et al., 2000; McCabe and Wolock, 2002; Zhang et al., 2001).”
It is clear that for most of Europe, there are no compelling real-world data to support the claim that the global warming of the past two centuries led to more frequent or severe flooding.
References
Bering Ovesen, N., Legard Iversen, H., Larsen, S., Muller-Wohlfeil, D.I. and Svendsen, L. 2000. Afstromningsforhold i danske vandlob. Faglig rapport fra DMU, no. 340. Miljo- og Energiministeriet. Danmarks Miljoundersogelser, Silkeborg, Denmark.
Climate Change Reconsidered: Website of the Nongovernmental International Panel on Climate Change. http://www.nipccreport.org/archive/archive.html
Douglas, E.M., Vogel, R.M. and Kroll, C.N. 2000. Trends in floods and low flows in the United States: impact of spatial correlation. Journal of Hydrology 240: 90-105.
Forland, E., Roald, L.A., Tveito, O.E. and Hanssen-Bauer, I. 2000. Past and future variations in climate and runoff in Norway. DNMI Report no. 1900/00 KLIMA, Oslo, Norway.
Hyvarinen, V. 2003. Trends and characteristics of hydrological time series in Finland. Nordic Hydrology 34: 71-90.
Klavins, M., Briede, A., Rodinov, V., Kokorite, I. and Frisk, T. 2002. Long-term changes of the river runoff in Latvia. Boreal Environmental Research 7: 447-456.
Lindstrom, G. and Bergstrom, S. 2004. Runoff trends in Sweden 1807-2002. Hydrological Sciences Journal 49: 69-83.
Lins, H.F. and Slack, J.R. 1999. Streamflow trends in the United States. Geophysical Research Letters 26: 227-230.
McCabe, G.J. and Wolock, D.M. 2002. A step increase in streamflow in the conterminous United States. Geophysical Research Letters 29: 2185-2188.
Mudelsee, M., Borngen, M., Tetzlaff, G. and Grunewald, U. 2003. No upward trends in the occurrence of extreme floods in central Europe. Nature 425: 166-169.
Nesje, A., Dahl, S.O., Matthews, J.A. and Berrisford, M.S. 2001. A ~4500-yr record of river floods obtained from a sediment core in Lake Atnsjoen, eastern Norway. Journal of Paleolimnology 25: 329-342.
Pirazzoli, P.A. 2000. Surges, atmospheric pressure and wind change and flooding probability on the Atlantic coast of France. Oceanologica Acta 23: 643-661.
Reynard, N.S., Prudhomme, C. and Crooks, S.M. 2001. The flood characteristics of large UK rivers: Potential effects of changing climate and land use. Climatic Change 48: 343-359.
Roald, L.A. 1999. Analyse av lange flomserier. HYDRA-rapport no. F01, NVE, Oslo, Norway.
Robson, A.J., Jones, T.K., Reed, D.W. and Bayliss, A.C. 1998. A study of national trends and variation in UK floods. International Journal of Climatology 18: 165-182.
Sheffer, N.A., Enzel, Y., Waldmann, N., Grodek, T. and Benito, G. 2003. Claim of largest flood on record proves false. EOS: Transactions, American Geophysical Union 84: 109.
Starkel, L. 2002. Change in the frequency of extreme events as the indicator of climatic change in the Holocene (in fluvial systems). Quaternary International 91: 25-32.
Zhang, X., Harvey, K.D., Hogg, W.D. and Yuzyk, T.R. 2001. Trends in Canadian streamflow. Water Resources Research 37: 987-998.
Haha, I like your last line! Thanks for your feedback!I mlopcetely agree but I feel those intricacies are becoming simplicities because of the way the technology has developed and now what the technology can do. I use FCE 4 and a lot of the edits are as simple as pressing a button and these programs are so forgiving that if you mess up its command+z and you are back to where you were before the mess up. It almost feels like the process will eventually get dumbed down to the point of click this to do that. About the quality and properness you are very right. The edits need to be made properly and followed by the rules of editing. Unless you read a book, take a class or learn second hand from someone who has read a book or taken a class, its not something that can just be guessed. It needs, how you said, the keenness and focus. Hopefully, if the process gets watered down the quality won't reflect.I do have to say, and I don't think I pressed this enough in the blog, the Editor is still in the equation if he is a member of the creation of the story from the start. I just remember hearing about this guy who wanted to make a 45 minute short and he gave his great footage (about an hour and 45 of good shots) to a friend who was masterful in the skills of editing. When the guy got the footage back it looked awful and he didn't like it at all. I'm positive the edits where right and the quality was superb but the story it was telling was wrong. I would be horrified by such a situation!
