Recent studies showed that anomalous dry conditions and limited moisture supply roughly between 1998 and 2008, especially in the Southern Hemisphere, led to reduced vegetation productivity and ceased growth in land evapotranspiration (ET). However, natural variability of Earth’s climate system can degrade capabilities for identifying climate trends. Here we produced a long-term (1982–2013) remote sensing based land ET record and investigated multidecadal changes in global ET and underlying causes. The ET record shows a significant upward global trend of 0.88 mm yr−2 (P < 0.001) over the 32-year period, mainly driven by vegetation greening (0.018% per year; P < 0.001) and rising atmosphere moisture demand (0.75 mm yr−2; P = 0.016). Our results indicate that reduced ET growth between 1998 and 2008 was an episodic phenomenon, with subsequent recovery of the ET growth rate after 2008. Terrestrial precipitation also shows a positive trend of 0.66 mm yr−2 (P = 0.08) over the same period consistent with expected water cycle intensification, but this trend is lower than coincident increases in evaporative demand and ET, implying a possibility of cumulative water supply constraint to ET. Continuation of these trends will likely exacerbate regional drought-induced disturbances, especially during regional dry climate phases associated with strong El Niño events.
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机译：最近的研究表明，大约在1998年至2008年之间，特别是在南半球，异常干燥的条件和有限的水分供应导致植被生产力下降，土地蒸散（ET）停止增长。但是，地球气候系统的自然变化会降低识别气候趋势的能力。在这里，我们制作了基于遥感的长期（1982-2013）土地ET记录，并调查了全球ET的数十年变化及其根本原因。 ET记录显示在32年期间全球上升趋势显着，为0.88 mm yr −2 （P <0.001），主要是由植被绿化（每年0.018％； P <0.001）和大气水分需求上升（0.75 mm yr −2 ； P = 0.016）。我们的结果表明，1998年至2008年间ET增长减少是一个典型现象，随后ET增长率在2008年之后恢复。陆地降水也显示出0.66 mm yr −2 的正趋势（P = 0.08）在同一时期内与预期的水循环强度一致，但是这种趋势低于蒸发需求和ET的同时增加，这意味着可能会累积限制ET的供水。这些趋势的持续下去可能会加剧区域干旱引起的干扰，特别是在与厄尔尼诺现象强烈相关的区域干旱气候阶段。
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