British climatologists modeled a possible change in the frequency of extreme weather events in 571 European cities by the second half of the 21st century. It turned out that even in the most optimistic scenario in most cities, the number of abnormally hot days will increase significantly, and their maximum temperature can grow by 7 degrees, according to scientists in Environmental Research Letters.

Now more than three quarters of the population of Europe lives in cities, and this share continues to grow. According to recent estimates, by the middle of the century it could reach 82 percent. Therefore, for example, in order to assess the possible impact of climate change on a person living in Europe, it is necessary to assess their consequences precisely for cities. Based on estimates of weather changes, it is possible to predict the risk of occurrence of periods of anomalous heat (similar to the one that was, for example, in Moscow in 2010) or floods from river spills. Such assessments will help reduce possible economic losses and reduce mortality.

To assess how in the near future European cities will change the frequency of extreme weather events: droughts, floods and abnormal heat - British climatologists led by Selma Gerrreiro (Selma B. Guerreiro) from Newcastle University modeled the climate changes that will take place in 571 European cities by the second half of the 21st century. To do this, scientists used one of the most reliable climate models CMIP5 and a high-level scenario of greenhouse gas emissions. Based on the results of the simulation, scientists obtained data for the amount of precipitation, maximum, average and minimum temperature. For all of these parameters, the authors analyzed the average annual and monthly mean values, based on which the amount and frequency of floods, droughts and periods of anomalous heat in summer periods were estimated. Data obtained by modeling for the period from 2051 to 2100, scientists compared with the average historical value from 1951 to 2000.

Because of the large number of uncertainties, the susceptibility of the urban climate to global climate change can not be accurately assessed, therefore for each city climatologists made estimates for three different scenarios: low weather, moderate and high climate change (they correspond to ten, fifty or ninety percent of the values , obtained as a result of modeling). Among other findings, scientists analyzed the possible maximum temperature during the heat wave, the duration of these periods, the possible increase in the frequency and risk of floods, the duration of periods of drought and the likelihood of exceeding temperature records.

It turned out that even in the case of the most optimistic scenario with the low impact of global climate changes on the weather, the number of abnormally hot days and their maximum temperature in most European cities will increase in the near future.

The strongest difference will be noticeable in the southern cities (in some of them the number of abnormally hot days can grow by 69 percent). In central Europe, the maximum temperature in hot periods can increase by a value from 2 to 7 degrees Celsius with an optimistic scenario and up to 14 degrees - with a pessimistic.

In the southern regions of Europe (in particular in the Iberian Peninsula), the probability of conditions contributing to frequent droughts will increase, and in northwest Europe, on the contrary, the frequency of floods may increase. Thus, according to the results of the survey, 85% of cities in the UK will noticeably increase the frequency of floods.

In the case of large cities, Madrid, Athens and Lisbon will be at the greatest risk of increasing droughts, the frequency of floods will increase in Dublin, Helsinki and Riga, and the number of days of anomalous heat will increase most in Rome, Stockholm, Prague and Athens. In this case, about one hundred cities will be at risk for two of these parameters, and 18 out of 571 cities are at risk for all the criteria considered by scientists.

One of the reasons for changing the frequency of extreme weather conditions in Europe is the scientists refer to the displacement of high-altitude jet streams in the upper layers of the troposphere over the North Atlantic from their habitual routes. As a result of deviations of atmospheric jets to the north or to the south leads to droughts and fires in Europe, and this effect is especially noticeable since the middle of the 20th century.

Source: nplus1.