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A report issued by World Weather Attribution has looked at climate change attribution of the flooding disasters in Libya and Greece.
Dr Karsten Haustein, Climate Scientist, Meteorologist, Leipzig University | Institute for Meteorology, said:
“The press release does reflect the science, including caveats (rather large uncertainties) and the huge role of vulnerability (providing a long and elaborate list of factors).
“The research is top notch and follows established WWAs rapid attribution principles, grounded in peer reviewed methods and data that pass highest quality standards.
“While the authors deviate from common practice to provide best estimates for the change in risk and intensity, they clearly justify why they did it. Most importantly, they explain why the results should be taken very seriously despite the rather large uncertainties. There simply are no physical factors that would counter their findings (which are in line with theoretical expectations as far as the central estimate is concerned). The limitation is that some a small number of climate models show reduced rainfall rates and that trend estimates based on observational data span a wide range of outcomes. But as with any attribution study, what matters is the big picture which undoubtedly indicates a moderate role of human-induced climate change in making the event worse (and much more likely to occur).
“As far as damage is Libya concerned, they discuss a host of confounding factors (long-lasting armed conflict, political instability, potential design flaws and poor maintenance of dams) that have led to an extreme level of vulnerability and exposure. All independent of climate change. Accordingly, they do not speculate about the role of climate change regarding damage and fatalities. Rather they highlight that the lack of early warning action and disaster relief has played a critical role in worsening the destructive outcome. The implications as far as adaptation is concerned are crucially important nonetheless, especially in light of the drastically increased risk for an event like this to happen again within the coming decades (rather than twice a millennium).”
Quotes provided by our colleagues at SMC Spain:
Robert Monjo, director of Research and Innovation at the Foundation for Climate Research and Associate Professor in the Department of Algebra, Geometry and Topology at the Complutense University of Madrid (UCM), said:
“In my view, the Daniel episode that affected Greece and then Libya may have been of greater intensity than would be expected with the historical climate because of the large volume of precipitable water now in the atmosphere, largely related to the huge thermal anomaly in the oceans. And with climate change, the oceans will undoubtedly continue to warm much more. Therefore, such intensities are more likely to recur in the very near future. The formation of Mediterranean cyclones is not a new phenomenon, and even assuming the possible doubts about whether they will form more frequently, what we can clearly state is that, once they do form, the intensity is directly related to the amount of precipitable water, which is increasing.
As far as the research is concerned, the first thing I must emphasise is the speed with which this study, which is so complicated from a climatological point of view, was carried out. The study is of more than sufficient quality to be taken into consideration. However, some minor comments are:
“The study period probably needs to be further extended to at least 100 years of historical data (observed or simulated) for the case of Libya. Mediterranean climate has so much variability that it is very difficult to find statistically significant trends in a few decades.
“It is very difficult to measure the probability of such extreme events that have a frequency of less than “once in 100 years”, as there are hardly any observed data to test and validate the models. Any record of previously unobserved hourly intensities is by definition an increase of “1 now versus 0 before”. Therefore, it is necessary to use theoretical functions to extrapolate a probability of phenomena that have never occurred. The technique of using theoretical distributions is very difficult to verify for variables such as precipitation as they are far away from typical Gaussian behaviour, as is the case for temperature.
“I think the authors should also use observed data from long weather stations (at least 50 or 100 years) to better analyse the return periods. Models and reanalyses are insufficient for these cases of extreme rainfall events [as in the case of those occurring in Spain]. In fact, the parameterisation of the models is, in general, more suited to typical rather than extreme rainfall situations, and therefore tends to underestimate sub-daily intensities”.
Pilar Brufau, researcher and Lecturer in the Department of Materials and Fluids Science and Technology at the University of Zaragoza, said:
“The WWA lists some of the causes of the disasters that have occurred in Greece, Bulgaria, Turkey, Libya and Spain in recent weeks from a rigorous point of view supported by observations and predictions of scientifically validated models, although not all of them could be considered as a consequence of climate change, as they point out in their report.
“The magnitude of the catastrophe in the case of Libya is not only due to rainfall, but also to the poor state of the dams, which has produced a chain disaster that could have taken place at any time and not because of the increase in global temperature or the greater accumulation of rainfall due to climate change.
“The same can be said in the case of Spain, where the damage can be caused by the well-known cold drop phenomenon, independently of global warming, although it is true that global warming can cause this type of event to intensify and even occur more frequently, as the scientists who carried out the analysis point out.”
Enrique Doblas, CREAF researcher, member of MedeCC (Mediterranean Experts on Climate Change and Environment) and author of the MAR1 report, said:
“It is certainly encouraging to see that this analysis, like our previous report, the First Mediterranean Assessment Report (MAR1) prepared by the independent network of Mediterranean Experts on Climate Change and Environment (MedECC), takes into account the factor of land use change. This reinforces our understanding that, while climate change can be seen as the underlying cause of recent catastrophes, its impacts are exacerbated by landscape management that lacks adequate preventive measures. Preventive measures in flood management play a key role in reducing risks and protecting communities. These measures include the development of early warning systems, the construction of check dams, the improvement of drainage systems and the implementation of emergency management plans. In addition, preventive measures based on urban planning for resilience and nature-based solutions offer a promising and economically viable approach. This includes actions such as reforestation in upstream areas, floodplain restoration and bank erosion protection, as well as appropriate agricultural practices to retain water. In addition, proactive adaptation to sea level rise is essential for coastal areas. We are talking about basic coastal adaptation practices, such as protection, strategies like beach and coastal accretion, as well as dune and wetland restoration, which are gaining ground as more sustainable alternatives to hard structures. These measures not only protect against flooding, but also contribute to preserving biodiversity and promoting long-term sustainability.”
“Interplay of climate change-exacerbated rainfall, exposure and vulnerability led to widespread impacts in the Mediterranean region” by World Weather Attribution (WWA) was published at 14:00 UK time on Tuesday 19th September.
Declared interests
Dr Karsten Haustein: No conflict of interest
For all other experts, no reply to our request for DOIs was received.