Frontier Science Center for Deep Ocean Multispheres and Earth System and Physical Oceanography Laboratory, Ocean University of China, Qingdao 266005, China.
Qingdao National Laboratory for Marine Science and Technology (QNLM), Qingdao 266005, China.
Proc Natl Acad Sci U S A. 2022 Feb 8;119(6). doi: 10.1073/pnas.2117832119.
Trends in surface air temperature (SAT) are a common metric for global warming. Using observations and observationally driven models, we show that a more comprehensive metric for global warming and weather extremes is the trend in surface equivalent potential temperature (Thetae_sfc) since it also accounts for the increase in atmospheric humidity and latent energy. From 1980 to 2019, while SAT increased by 0.79[Formula: see text], Thetae_sfc increased by 1.48[Formula: see text] globally and as much as 4[Formula: see text] in the tropics. The increase in water vapor is responsible for the factor of 2 difference between SAT and Thetae_sfc trends. Thetae_sfc increased more uniformly (than SAT) between the midlatitudes of the southern hemisphere and the northern hemisphere, revealing the global nature of the heating added by greenhouse gases (GHGs). Trends in heat extremes and extreme precipitation are correlated strongly with the global/tropical trends in Thetae_sfc. The tropical amplification of Thetae_sfc is as large as the arctic amplification of SAT, accounting for the observed global positive trends in deep convection and a 20% increase in heat extremes. With unchecked GHG emissions, while SAT warming can reach 4.8[Formula: see text] by 2100, the global mean Thetae_sfc can increase by as much as 12[Formula: see text], with corresponding increases of 12[Formula: see text] (median) to 24[Formula: see text] (5% of grid points) in land surface temperature extremes, a 14- to 30-fold increase in frequency of heat extremes, a 40% increase in the energy available for tropical deep convection, and an up to 60% increase in extreme precipitation.
气温趋势是衡量全球变暖的常用指标。我们利用观测数据和观测驱动的模型表明，衡量全球变暖及极端天气的更全面指标是地表等效位温（Thetae_sfc）的趋势，因为它还考虑了大气湿度和潜热的增加。1980 年至 2019 年，尽管气温上升了 0.79°C，但全球地表等效位温上升了 1.48°C，热带地区上升了高达 4°C。水汽的增加是气温和地表等效位温趋势差异的 2 倍的原因。南半球和北半球中纬度之间的地表等效位温增加更加均匀（比气温增加更均匀），揭示了温室气体（GHGs）增加的全球性质。极端高温和极端降水的趋势与全球/热带地表等效位温的趋势密切相关。地表等效位温的热带放大与气温的北极放大一样大，这解释了观测到的深层对流的全球正趋势和极端高温的 20%的增加。如果不控制温室气体排放，到 2100 年，气温可能上升 4.8°C，而全球平均地表等效位温可能上升高达 12°C，相应地，陆地表面温度极端值可能增加 12°C（中位数）至 24°C（5%的网格点），极端高温的频率增加 14 至 30 倍，热带深层对流可用能量增加 40%，极端降水增加高达 60%。
