二维能量平衡模式中大气温度对二氧化碳增温效应的响应

Response of atmospheric temperature to CO_2 warming effect in a 2-dimensional energy balance model.

利用一个考虑了辐射能传输的二维能量平衡气候模式,解析地分析了二氧化碳浓度改变后冰界纬度的变化,得到了冰界纬度随CO_2浓度变化的关系以及全球平均温度的变化曲线。结果表明,当CO_2浓度由工业革命前的280×10^(-6)增加到700×10^(-6)时,冰界仅后退(北半球向北)几个纬度;当CO_2的浓度继续增加时,冰界纬度会加速向极地退缩,直至出现全球无极冰覆盖的现象。同样地,当CO_2浓度由280×10^(-6)增加到700×10^(-6)时,全球地表平均温度虽然在增加,但增加的速率很小,并且增加的速率在减小,而当大于700×10^(-6)之后,温度增加的速率会快速增大,温度将加速上升。对不同反照率进行敏感性试验,发现当反照率从0.1到0.32时,结果并没有显著地改变,即结果对反照率的变化并不敏感。这一计算结果表明,在目前的状态下,由CO_2引起的增温作用似乎处于变化很小的准饱和状态,即目前气候不会因为CO_2浓度的增加而迅速变暖。较为实际的情形可能是大气温度在缓慢增加到一定程度后才会迅速升高。这并不意味着可以忽视CO_2的增温效应,因为根据计算结果,这个临界值大概在700×10^(-6)左右,当CO_2浓度增加到超过临界值之后,气温会剧烈上升,气候将会处在一个非常温暖的阶段。

A 2-dimensional climate model is established,which considers the radiant energy transfer process.Through using it,the relationship between the ice line latitude and concentration of CO_2 as well as the curve of mean global surface temperature change with concentration of CO2 are analytically gained.And then an explicit analysis has been made and some interesting results have been obtained. It is suggested that if the concentration of CO2 increases from the level of 280×10-6 in pre-industrial era to 700×10-6,the ice line will recede northward by several latitudes（in the North Hemisphere）;while the concentration continues to increase,there will be a quick receding and even no ice covers the earth eventually.Accompanying with this,the mean global surface temperature will rise, with a slowed down increasing velocity before the level of 700×10-6 reached but an accelerating rate after 700×10-6.To verify the impact of albedo,the different albedo values ranged from 0.1 to 0.32 are tested.It is found that with the change of albedo the results vary little.The model does not have much sensitivity to albedo.According to the calculation,the warming effect incited by CO2 seems to tend to approach a quasi-saturated state in the current situation,that is,the climate system will not transform fast to a warming globe due to the increase of CO2.A more realistic circumstance might be that the global temperature will rise robustly after an andante increasing.According to the computational results,this critical value is near 700×10-6.However,that does not mean the warming effect of CO2 can be ignored.It can be implied from the results that the climate will be in a very warm state and the temperature will rise robustly after exceeding the critical value.