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July heatwave has multiple impacts
2019-08-01 10:30:00 来源: WMO
For the second time in one month, a widespread and intense heatwave impacted Europe, with many new maximum and minimum temperature records, causing disruption to transport and infrastructure and stress on people\'s health and the environment. As the heat dome spread northwards through Scandinavia and towards Greenland, it accelerated the already above average rate of ice melt.Such heatwaves are consistent with what we expect from climate change and rising global temperatures.Belgium, Germany, Luxembourg, the Netherlands and the United Kingdom saw new national temperature records on 25 July, as weather maps were redrawn to include – for the first time – temperatures of above 40°C. Paris recorded its hottest day on record, with a temperature of 42.6 °C at 1632, an unprecedented value since the beginning of measurements.The heatwave was caused by warm air coming up from North Africa and Spain and this was then transported from Central Europe to Scandinavia,  Norway saw new station records on 27 July, and 28 locations had “tropical nights” above 20°C.  The Finnish capital Helsinki set a new station record of 33.2°C on 28 July and in the south of Finland, Porvoo saw a temperature of 33.7°C.The anomalously high temperatures are expected to enhance melting of the Greenland ice sheet, which already . The persistent high melt and runoff in the last few weeks means the season total is running near tothe 2012 record high loss, according to monitoring the Greenland ice sheet.. At Summit Camp station, at the peak of the ice sheet and at an altitude of 3200m, a temperature of 0.0°C was measured.“It is important to remember that that any given day or year, ice sheet surface mass budget is a result largely of weather, though with the background climate trend affecting this,” , a climate scientist with the Danish Meteorological Institute.This will also impact Arctic sea ice, which where the loss of ice extent through the first half of July matched loss rates observed in 2012, the year which had the lowest September sea ice extent in the satellite record, according to the US National Snow and Ice Data Center.The high temperatures also fanned wildfire activity in the Arctic, including in Greenland, Alaska and Siberia.The Russian Federal Forestry Agency estimates that, as of 29 July,  wildfires in Siberia  have burned 33.2 thousand hectares, with 745 active fires, causing massive ecological devastation and impacting air quality for hundreds of kilometres.  .The European Centre for Medium-Range Weather Forecasts/Copernicus Atmosphere Monitoring Service estimated that July 2019 wildfire CO2 emissions for the Arctic Circle totalled 75.5047 megatonnes, which is comparable to the 2017 annual fossil fuel emissions of Colombia. This was more than double July 2018 levels, and followed a record month in .  “By burning vegetation, the fires also reduce the capacity of the biosphere to absorb carbon dioxide. Action against climate change necessitates rather that we should expand this capacity,” said Oksana Tarasova, Chief of WMO’s Atmosphere and Environment Research Division.   The July heatwave follows an unusually early and exceptionally intense heatwave in June, which set new temperature records in Europe and ensured that the month of June was the hottest on record for the continent, with the average temperature of 2° Celsius above normal..In parts of Europe, the heat was accompanied by below-average precipitation. On 31 July, WMO’s regional climate monitoring centre for Europe, operated by the Deutscher Wetterdienst, updated its Climate Watch advisory on drought. This provides guidance to national meteorological and hydrological services in issuing climate advisories for their territory.“A continuation of drought conditions and below-normal precipitation in large parts of Central and Northeastern Europe. In these areas mostly only 60-80 % of normal precipitation was recorded in June, in some parts even less. There was also only scarce rainfall in July and forecasts show continued below-normal precipitation in most of the area with weekly deficits of partly 10-30mm for this week with  a probability of 80% and higher,” it said.“Next week, above-normal precipitation will be expected over Central Europe, but this might not be sufficient to compensate for the rain deficits during the weeks before and therefore soils will be still dry. Northeastern Europe (Baltic countries and southern Finland) will still receive not more than below-normal to normal precipitation next week and therefore drought conditions are likely to continue. Drought conditions can result in harvest losses, forest fires, lack of animal food water restrictions, restrictions of ship traffic due to low water levels.“During the heatwave, national meteorological and hydrological services issued heat alerts - including the top-level red alert - and, in some areas, fire warnings to minimize the risk to life and the environment. Heat-health action plans mobilized  civil protection efforts across the region. Heat events kill thousands of people every year and often trigger secondary events such as wildfires and failures to electrical grids.  Urbanization compounds the problem. Heat stroke, dehydration, cardiovascular and other temperature related diseases are major health risks.The new absolute record of 42.6°C for Paris was recorded on 25 July at the centennial weather station in Paris-Monsouris, and broke the previous record dating back to 28 July 1947 with 40.4 °C. This temperature is typical of the average July temperature in Bagdad, Iraq.  The night of 24/25 July was also exceptionally hot, with minimal temperatures above 25°C and even 28.3°C in a downtown Paris weather station. What is striking is the margin with which the records were beaten. Lille recorded 41.4°C, that’s nearly 4°C above the previous record. France set a new national temperature record of 46°C during the last  on 28 June.   It was only the second time Météo-France has ever issued red level warnings for a heatwave in France. The first time was during June\'s heatwave when several departments in the south were put on red alert. But it is unprecedented for Paris and the north of the country to be on a red alert for a heatwave. Thousands of hectares were burned by wildfires in northern France, where it is very unusual to see wildfires.The German Weather Service, Deutscher Wetterdienst, described 25 July as “a day which will make weather history.” Germany set a new national temperature record (provisional figure) of 42.6°C in Lingen, near the Dutch border, defeating the old record by 2.3 °C. There were 25 weather stations above 40 °C. The previous national temperature record was 40.3°C (5 July 2015).     The  broke a 75-year-old heat record (set in Aug 1944) with a temperature of 40.7°C at Gilye Rijen. Beigium also set a new national record of 41.8°C. Luxembourg set a new national record of 40.8°C. Temperatures in the United Kingdom reached 38.7 Celsius at Cambridge Botanical Gardens, beating the previous record of 36.7°C set in Heathrow in 2015, according to the .  In parts of Europe, the heatwave was followed by very heavy precipitation.Many scientific studies have been conducted on the links between climate change and heatwaves."Every heatwave occurring in Europe today is made more likely and more intense by human-induced climate change," said a study published by scientists at World Weather Attribution on the  "The observations show a very large increase in the temperature of these heatwaves. Currently such an event is estimated to occur with a return period of 30 years, but similarly frequent heatwaves would have likely been about 4 ºC cooler a century ago. In other words, a heatwave that intense is occurring at least 10 times more frequently today than a century ago," it said.In its Fifth Assessment Report (2014), the Intergovernmental Panel on Climate Change said that “it is very likely that human influence has contributed to the observed global scale changes in the frequency and intensity of daily temperature extremes since the mid-20th century. It is likely that human influence has more than doubled the probability of occurrence of heat waves in some locations.”In its 2018 report on Global Warming of 1.5°C, the IPCC said that climate-related risks to health, livelihoods, food security, water supply, human security, and economic growth are projected to increase with global warming of 1.5 °C and increase further with 2 °C.Limiting warming to 1.5 °C rather than 2 °C could result in 420 million fewer people being exposed to severe heatwaves, it said.Between 2000 and 2016, the number of people exposed to heatwaves was estimated to have increased by around 125 million persons, as the average length of individual heatwaves was 0.37 days longer, compared to the period between 1986 and 2008, according to the World Health Organization. Many countries have issued national climate assessments and scenarios which underline the close connection between climate change and heat. For instance, the  report showed an increase in higher maximum temperatures and longer warm spells. The hottest day of the year for the most recent decade (2008-2017) has increased by 0.8°C above the 1961-1990 average. Warm spells have also more than doubled in length – increasing from 5.3 days in 1961-90 to over 13 days in the most recent decade (2008-2017).
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