气候系统对CO_2强迫和太阳辐射强迫在不同时间尺度的响应

Climate Response to Carbon Dioxide Forcing and Solar Radiation Forcing on Different Time Scales

使用Had CM3L气候模式,针对突然增加的4倍CO_2浓度和增加4%的太阳辐射强迫进行一系列理想化模拟试验,分析并比较了CO_2强迫和太阳辐射强迫对气候系统的影响机制和异同。模拟结果表明,突然增加的4倍CO_2浓度和增加4%的太阳辐射造成的长期全球表面平均温度变化基本相同,但二者造成降水的变化差异很大。气候系统对CO_2和太阳辐射的响应可以分为快响应和慢响应两个部分,而降水的差异主要体现在大约1个月时间尺度内的快响应阶段,在这一时间段,陆地区域CO_2的气孔效应减少了植被的蒸腾作用,导致降水受到抑制;海洋区域CO_2的辐射效应会首先导致大气长波吸收增强,而海洋的比热较大,所以海表温度变化落后于低层大气,低层大气的垂直稳定度增加,海表向上蒸发受到抑制。此外,比较不同时间尺度上CO_2对气候系统的影响,可以发现在1个月的短时间尺度上,对陆地而言,CO_2的气孔效应对气候系统的影响占主导地位,但在数年以上更长的时间尺度上,CO_2的辐射效应是导致地气系统温度升高的主要原因。

The HadCM3L climate model was used to investigate climate response to an abrupt quadrupling of atmospheric CO2 and 4% increase in solar irradiance. Modeling results show that a quadrupling of CO2 and 4% increase in solar irradiance cause approximately the same global mean surface temperature change by the end of 1000-year simulations, but the precipitation responses are substantially different. The difference is mainly due to the different fast response of the climate system, which occurs over a short time period （about one month） before sea surface warms significantly. During this period, over land, the physiological effect of CO2 reduces the plant transpiration. Over ocean, the radiation effect of CO2 leads to the increase of the temperature in the lower atmosphere, which occurs much faster than the warming of sea surface temperature. This increases vertical stability of the lower atmosphere, suppressing evaporation over ocean. Consequently, during the period of fast response （about one month）, precipitation decreases in land and ocean areas. Compare to the effects of physiological effects of CO2, the radiation effect of CO2 has more important effect on the climate system at the time scale longer than a few years. But on a short time scale of one month, the physiological effect of CO2 has a greater impact over land.