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主题:解读IPCC报告关于大气[CO2]加倍对对气候的定量影响 -- hwd99

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家园 解读IPCC报告3 直接气候敏感因子

3直接气候敏感因子 non-feedback climate sensitivity factor

定义:k0=dT/dRf0

T 代表气温(地球近表面大气温度)

Rf 代表辐射强迫

dRf0 是不考虑反馈效应条件下的直接辐射强迫变化,引用报告中定义,参见AR4 wg1 第8章, pp631。翻译如下:

在理想情况下,包括无反馈效应(但包括温度升高导致的增强的辐射冷却效应),均一的温度变化,大气二氧化碳加倍导致的气候响应,根据GCM(Global circulation model,全球环流模型)的全球增温是1.2K(Hansen et al., 1984; Bony et al., 2006)。水蒸汽反馈效应,单独计算,至少使效应加倍6。

(6此处是脚注:在这些简化假设下,根据反馈参数λ确定的,反馈效应产生的放大倍数是1/(1+λ/λp), 此处λp是均一温度下,辐射冷却响应参数,根据Bony et al(2006)约为-3.2 K/(W/m2), 如果有n个独立反馈,则用(λ1 +λ2 +..λn ) 代替λ。)

(原文如下:

In the idealised situation that the climate response to a doubling of atmospheric CO2 consisted of a uniform temperature change only, with no feedbacks operating (but allowing for the enhanced radiative cooling resulting from the temperature increase), the global warming from GCMs would be around 1.2°C (Hansen et al., 1984; Bony et al., 2006). The water vapour feedback, operating alone on top of this, would at least double the response.6

6 Under these simplifying assumptions the amplifi cation of the global warming from a feedback parameter λ(in W m-2 °C–1) with no other feedbacks operating is 1/(1+λ/λp), where λp is the ‘uniform temperature’ radiative cooling response (of value approximately –3.2; Bony et al., 2006). If n independent feedbacks operate, λis replaced by (λ1 +λ2 +..λn ).)

这里引用的,无反馈条件下,大气二氧化碳浓度加倍,全球增温1.2K,引文来自Hansen et al (1984)及 Bony et al (2006)。根据该数据,可以估算直接气候敏感因子。Hansen在计算这个数据时(来自Hansen 文章表1),同时给出了计算得到的无反馈辐射强迫变化,约为4W/m2, (The initial radiative imbalance at the top of the atmosphere due to doubling C02 is only -2.5 W m-2, but after C02 cools the stratosphere (within a few months) the global mean radiative forcing is about 4 W m-2 (Fig. 4, Hansen et al.,1981,翻译如下:在起始辐射非平衡下,二氧化碳加倍导致的大气层顶辐射强迫变化是-2.5 W/2,但是,几个月后,由于二氧化碳冷却平流层,使辐射强迫变为约4W/m2).这说明k=1.2/4=0.3K/(W/m2)。

Hansen在该文中,还给出另一个数据是0.29,这是根据等式14 ΔTs(K)~0.29ΔF(W/m2) 得到的,但是,该数据并不是二氧化碳加倍引起的辐射强迫变化,原文:A flux of 1 W m-2 was arbitrarily added to the ocean surface, and the lapse rate, water vapor and other radiative constituents were kept fixed. The surface temperature increase at equilibrium was 0.29K. implying eq14 (翻译:在海洋表面强制加入1W/m2辐射,同时保持温度下降速率,空气中水蒸气和其它辐射组分保持不变,得到平衡升温0.29K,从而得到14式)。

在Bony等的综述文章中,并没有提到无反馈条件下,大气二氧化碳浓度加倍,全球增温1.2K,但是,在附录中,引用Colman (2003) 及Soden 和Held (2006) 文章,给出了λ=3.2 K/(W/m2).

原文:The Planck feedback parameter λP is negative (an increase in temperature enhances the LW emission to space and thus reduces R) and its typical value for the earth’s atmosphere, estimated from GCM calculationsA1 (Colman 2003; Soden and Held 2006), is about _3.2 W m_2 K_1 (a value of _3.8 W m_2 K_1 is obtained by defining λP simply as 4σT3, by equating the global mean OLR to σT4,and by assuming an emission temperature of 255 K).

其中,Colman的文章没有提到这个数据,而是引用了Hansen的温升1.2K(1984)。原文Assuming ΔT0 =1.2 (Hansen et al. 1984) and taking K =0.3K/(W/m2) from quoted model results, noted in the discussion of method 2, permits calculation of Ki。这说明Colman使用的直接气候敏感因子是0.3.

Solden和Held则在其文章表1中给出了14种模型计算得到的结果,范围是3.13-3.26,平均值约为3.20。这个数据暗示 k=1/λ=0.313K/(W/m2). 这个数据应是报告的唯一来源数据。


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