A new study concludes that when placed into a long-term context recent drought events in Europe are within the range of natural variability and are not unprecedented over the last millennium.
The 2003 European heatwave and drought has a special place in the history of the study of our changing climate. It was the first event that scientists attributed to human-induced climate change. A paper by Stott et al published in Nature concluded, “Human influence has at least doubled the risk of a regional heatwave like the European Summer of 2003.” This was later strengthened and the event was said to be directly caused by humans.
Alongside the increasing attribution of such events to human-influence has been the assertion that the incidence of droughts is on the rise, along with their human toll. Looking back at 2004 Peter Stott of the UK Met Office has written that at that time “heatwaves, floods and droughts were on the rise.
This was a view that was at odds with the science, in 2004 and for many years afterwards. In 2013 the IPCC AR5 report said there was low confidence that droughts had increased. But by AR6, just eight years later, the situation had changed. AR6 said that there was now medium confidence that droughts had increased, but then it goes on to say, “there is low confidence that human influence has affected meteorological droughts in most regions but medium confidence that they have contributed to the severity of some specific events. It add that there is medium confidence that human-induced climate change has contributed to increasing trends in the probability or intensity of recent agricultural and ecological droughts.” So, AR6 has a set of contradictory stances.
Some, however, exhibit no such equivocation. In the epilogue to his book “Hot Air,” Peter Stott says, “The global toll from floods, droughts and heatwaves continues to rise at a startling rate, their increasing intensity attributable, our research shows, to human-induced climate change.”
Europe in the 21st Century has experienced a series of long-lasting dry and hot summers. Anthropogenic Global Warming (AGW) was also considered the culprit behind a heatwave and drought in Russia in 2010, and again in Europe in 2013, 2015 and 2018. There is no doubt, according to a group of scientists studying the attribution of such weather events to AGW, that they are unusual enough to have been the specific result of AGW. The website Carbon Brief labelled recent droughts as unprecedented.
But are they? Writing in the journal Nature Monica Ionita from the Alfred Wegner Institute Helmholtz Center for Polar and Marine Research, Bremerhaven, Germany. Along with colleagues from the Faculty of Physics, Bucharest University, the Faculty of Forestry, Ștefan cel Mare University, Suceava, Romania, and Bremen University ask if the data is really good enough to determine if these recent events are all that unusual. They use several independent datasets, observations, paleo data reanalysis, historical evidence and climate/weather proxies, to gather a picture of changes over the past thousand years or so.
They find that between 1901 -2012 the driest years in Europe were 1921 and 1976 and in the past thousand years they were 1102, 1503, 1865 and 1921. During the past millennium there were two megadroughts in Central Europe, in 1400-1480 and 1770-1840.
They conclude that when placed into a long-term context recent drought events are within the range of natural variability and they are not unprecedented over the last millennium. Their conclusion that recent drought events are nothing unusual stands on its own, the researchers however go further and consider their climatic influences. They note that the two megadroughts appear to be linked with a cold state of the North Atlantic Ocean and increased frontal blocking activity over the British Isles and the western part of Europe. They also note that they are also coincident with the Sporer and Dalton minima of solar activity.
The researchers add that future climate projections indicate that Europe will face substantial drying, even for the least aggressive emission pathways scenarios. They say that although the greenhouse gases and their associate global warming will contribute to future drought risk their study indicates that future drought variations will also be strongly influenced by natural variations. In particular a possible decrease in total solar irradiance over the next few decades and its concomitant effects on the earth could result in a higher frequency of drought events in central Europe, which could add to the drying induced by AGW. They recommend further work on how the combined effect of natural and anthropogenic factors will shape the drought magnitude and frequency.
The conclusions of this research should be considered alongside claims about droughts made by some scientists involved in climate attribution studies. Some will dismiss it as being “just one paper,” but that would be unscientific. Perhaps we don’t appreciate just how variable climate is or consider too short a timescale when deciding that heatwaves, floods and droughts are on the rise?
There are statistical and philosophical questions surrounding the process of climate attribution. How does one assess what would have happened in the absence of rising greenhouse gas influence? How does one compare our planet today, with a hypothetical planet B? It’s an approach enthusiastically supported by some but not by everyone. At the recent GWPF annual lecture Professor Steven Koonin of New York University said climate attribution studies were the scientific equivalent of being told you had won the lottery, after you had won the lottery.