温室气体诱导的渐变气候效应

A STUDY OF THE TRANSIENT AND TIME-DEPENDENT GREENHOUSE GAS-INDUCED CLIMATE CHANGE

本文设计了一个能量平衡模式（ＥＢＭ）和改进的箱室扩散（ＢＤ＊）海洋模式的耦合模式（ＥＢＭ／ＢＤ＊），模拟了大气中ＣＯ２浓度突然加倍和近百年来由于大气中温室气体浓度增加引起的全球地表气温变化，详细地讨论了海洋对全球气温变化的延缓作用，并对下一个世纪大气中ＣＯ２浓度变化及其诱导的全球地表气温变化进行了数值分析。

Greenhouse gas-induced global climate change has been attracted much attention in recent years. Model studies suggest that the equilibrium warming for a CO2 doubling is 1. 5 ℃-4.5℃ (climate sensitivity). However. because the huge thermal capacity of the ocean will delay and effectively reduce the climate response to the increase in the concentration of the greenhouse gases, at a given time, the realized global surface temperature will only reflect part of the equilibrium change for the corresponding instantaneous value of the radiative forcings induced by greenhouse-gases. In this study, we have developed a coupled EBM/BD model to study the greenhouse-gas induced transient and time-dependent change of global mean temperature. The model consists of three parts, i. e., the atmosphere, land and ocean. The atmosphere and the land are considered as boxes. The ocean is divided into a oceanic mixed layer, a thermocline layer and a bottom layer. The heat exchanges of atmosphere-land,atmosphere-oceanic mixed layer and land-oceanic mixed layer are described by using the energy balance model developed by Wigley and Schlesinger. The heat exchanges of oceanic mixed layer-thermocline layer, mixed layer-bottom layer and thermocline layer-bottom layer are described by using our BD model previously developed for study of the carbon circle. The validity of the model is investigated by comparing the simulated and observed vertical distributions of ocean water temperature. A doubling CO2 experiment is performed to investigate the response of the ocean surface temperature to the increase in the concentration of the greenhouse gases. In the experiment,the radiative forcing due to doubling CO2 is 4. 23w/m2. The results show that the thermal inertia of the ocean provides a time lag of about 1 1. 08- 101. 48 years, depending on the values of climate sensitivity. The model is also used to simulate the variation of the ground surface temperature in the past 100 years by using the radiative forcings derived from the concentrations of greenhouse gases given by Wigley. The results show that the ground surface temperature has risen about 0. 35-0. 64℃. corresponding to the climate sensitivity of 1. 54-4.5℃. Such results are consistent with the observed rise of about 0. 3℃-0. 6℃. The consistence between the simulated and observed rise of the ground surface temperature indicates that the increase in the concentrations of the greenhouse gases plays a main role in the rise of the ground surface temperature in the past 100 years. The CO2 concentration of the next century has been simulated by using the BD model for several emission scenarios given by IPCC. If the humankind does not control the CO2 emissions from now. the CO2 concentration will reach a value of 743ppmv at the end of the next century. If the CO2 emissions are reduced at a rate of 2% per year. the CO2 concentration will slowly increase until 2050 and reach a peak value of 390ppmv. After 2050, the CO2 concentration will decrease. If the CO2 emissions are stopped from now, the CO2 concentration will slowly decrease and reach a value of 320ppmv at the end of the next century. The variations of the ground surface temperature of the next century are estimated by using the coupled model. The results show that. if the humankind does not control the CO2 emissions, the ground surface temperature at the end of the next century will rise about 1. 64℃-3. 08℃ for the climate sensitivity of 1. 5℃-4. 5℃. If the CO2 emissions are reduced at a rate of 2% per year, the ground surface temperature will slowly rise in the beginning and middle decades of the next century. The ground surface temperature will not change in the late decades. If the CO2 emissions can be stopped from now, The ground surface temperature will decrease slowly.