School of Environmental Engineering, Technical University of Crete, Greece.
Sci Total Environ. 2019 Mar 10;655:482-511. doi: 10.1016/j.scitotenv.2018.11.215. Epub 2018 Nov 18.
Drylands are vital ecosystems which cover almost 47% of the Earth's surface, hosting 39% of the global population. Dryland areas are highly sensitive to climatic changes and substantial impacts are foreseen under a warming climate. Many studies have examined the evolution of drylands in the future highlighting the need for improved capability of climate models to simulate aridity. The present study takes advantage of new higher resolution climate projections by the HadGEM3A Atmosphere Global Climate Model using prescribed time varying SSTs and sea ice, provided by a range of CMIP5 climate models under RCP8.5. The aim of the higher resolution models is to examine the benefit of the improved representation of atmospheric processes in the dryland research and to see where these results lie in the range of results from previous studies using the original CMIP5 ensemble. The transient response of aridity from the recent past until the end of the 21st century was examined as well as the expansion of global drylands under specific levels of global warming (1.5 °C, 2 °C and 4 °C). Dryland changes were further assessed at the watershed level for a number of major global river basins to discuss implications on hydrological changes and land degradation. The areal coverage of drylands could increase by an additional 7% of the global land surface by 2100 under high end climate change. At a 4 °C warmer world above pre-industrial, 11.2% of global land area is projected to shift towards drier types and 4.24% to wetter. At the same level of warming the number of humans projected to live in drylands varies between 3.3 and 5.2 billion, depending on the socioeconomic developments. By keeping global warming levels to 1.5 °C, up to 1.9 billion people could avoid living in drylands compared to a 4 °C warmer world of low environmental concern.
旱地是至关重要的生态系统，覆盖了地球表面的近 47%，承载着全球 39%的人口。旱地对气候变化极为敏感，在气候变暖的情况下，预计会产生重大影响。许多研究都考察了未来旱地的演变，强调了气候模型模拟干旱能力需要提高。本研究利用 HadGEM3A 大气全球气候模型提供的新的高分辨率气候预测，该模型使用了一系列 CMIP5 气候模型规定的时变海表温度和海冰，这些预测是在 RCP8.5 下提供的。高分辨率模型的目的是考察改进大气过程在旱地研究中的代表性的益处，并了解这些结果在使用原始 CMIP5 集合的先前研究结果范围内的位置。研究考察了从最近过去到 21 世纪末干旱的瞬态响应，以及在特定的全球变暖水平（1.5°C、2°C 和 4°C）下全球旱地的扩张。还在一些主要全球流域的流域水平上进一步评估了旱地变化，以讨论对水文变化和土地退化的影响。在高排放情景下，到 2100 年，全球旱地面积可能会在全球陆地表面额外增加 7%。在比工业化前高 4°C 的世界中，预计全球 11.2%的陆地面积将向更干燥的类型转变，4.24%将向更湿润的类型转变。在同样的变暖水平下，预计生活在旱地的人数在 33 亿至 52 亿之间，具体取决于社会经济发展。如果将全球变暖水平控制在 1.5°C，与全球变暖 4°C 的低环境关注世界相比，多达 19 亿人可以避免生活在旱地。
