摘要
Understanding the role of anthropogenic forcings in regional hydrological changes can help communities plan their adaptation in an informed manner.Here we apply attribution research methods to investigate the effect of human influence on historical trends in wet and dry summers and changes in the likelihood of extreme events in Europe.We employ an ensemble of new climate models and compare experiments with and without the effect of human influence to assess the anthropogenic contribution.Future changes are also analysed with projections to year 2100.We employ two drought indices defined relative to the pre-industrial climate:one driven by changes in rainfall only and one that also includes the effect of temperature via changes in potential evapotranspiration.Both indices suggest significant changes in European summers have already emerged above variability and are expected to intensify in the future,leading to widespread dryer conditions which are more extreme in the south.When only the effect of rainfall is considered,there is a distinct contrast between a shift towards wetter conditions in the north and dryer in the south of the continent,as well as an overall increase in variability.However,when the effect of warming is also included,it largely masks the wet trends in the north,resulting in increasingly drier summers across most of the continent.Historical index trends are already detected in the observations,while models suggest that what were extremely dry conditions in the pre-industrial climate will become normal in the south by the end of the century.
了解人为因素在区域水文变化中的作用有助于人们制定适应策略.本文应用归因研究方法调查了欧洲地区人为因素对干、湿夏季的历史变化趋势以及发生极端事件可能性的影响.采用了一组新的气候模式,比较有无人类影响的实验来评估人类活动的贡献,并基于至2100年的预估结果分析了未来变化.应用了两个相对于工业化前气候定义的干旱指数分析.这两个指数:一个仅由降雨变化驱动,另一个还包括潜在蒸散量变化产生的温度的影响.两个指数分析均表明,欧洲夏季干湿变化已经显著超出其自然变率,且预计未来将加剧,导致南部出现更为极端的大范围干状况.如果只考虑降雨的影响,欧洲大陆北部变得更湿润,而南部变得更干燥且总体变率增加.然而,当把增温影响也考虑在内时,它在很大程度上掩盖了北部的增湿趋势,导致整个欧洲大陆的夏季越来越干.虽然观测数据揭示了干、湿夏季历史指数的趋势,但模型研究表明,前工业时代的极端干状况在21世纪末将在欧洲南部成为正常现象.
基金
supported by the Met Office Hadley Centre Climate Programme funded by the Department for Business,Energy&Industrial Strategy(BEIS)
the Department for Environment,Food&Rural Affairs(Defra)
supported by the European Prototype demonstrator for the Harmonisation and Evaluation of Methodologies for attribution of extreme weather Events(EUPHEME)project,which is part of the European Research Area for Climate Services(ERA4CS),a European Research Area Network(ERA-NET)initiated by the Joint Programming Initiative‘‘Connecting Climate Knowledge for Europe”(JPI Climate)and co-funded by the European Union(690462)。
