How positive is the feedback between climate change and the carbon cycle?
How positive is the feedback between climate change and the carbon cycle?
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DOI：
10.3402/tellusb.v55i2.16765
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发表时间：
2003-01
期刊：
影响因子：
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通讯作者：
P. Friedlingstein;J. Dufresne;P. Cox;P. Rayner
中科院分区：
文献类型：
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作者：
P. Friedlingstein;J. Dufresne;P. Cox;P. Rayner
大气温室气体排放引起的未来气候变化被认为对全球碳循环产生重大影响。几项关注海洋或陆地碳循环的离线研究突出了这种潜在影响。最近的两项在线研究使用海洋-大气环流模型与陆地和海洋碳循环模型耦合，以一致的方式调查了气候变化与碳循环之间的反馈。这两项研究使用观测到的1860-1995年期间的人为二氧化碳排放和IPCC 1995-2100年期间的情景来强迫气候-碳循环模式。哈德利中心小组的研究显示了一个非常大的正反馈，如果未来的气候影响碳循环，大气二氧化碳到2100年将达到980 ppmv，但如果包括碳循环，但假设对气候变化不敏感，则只有700 ppmv左右。IPSL耦合气候-碳循环模型模拟了一个小得多的正反馈：到2100年，气候对碳循环的影响导致大气中碳的增加量小于100 ppmv。在这里，我们进行了详细的反馈分析，以表明这种差异是由于两个关键过程在这些耦合模型中仍然缺乏约束：第一是南大洋环流，它主要控制地球化学对CO2的吸收，第二是植被和土壤碳对全球变暖的响应。我们的分析结果与完全耦合模型得到的结果非常吻合。它还允许我们确定，在上面提到的两个过程中，后者（土地对全球变暖的反应）是一个本质上解释IPSL和哈德利结果之间差异的过程。
Future climate change induced by atmospheric emissions of greenhouse gases is believed to have a large impact on the global carbon cycle. Several offline studies focusing either on the marine or on the terrestrial carbon cycle highlighted such potential effects. Two recent online studies, using ocean—atmosphere general circulation models coupled to land and ocean carbon cycle models, investigated in a consistent way the feedback between the climate change and the carbon cycle. These two studies used observed anthropogenic CO2 emissions for the 1860–1995 period and IPCC scenarios for the 1995–2100 period to force the climate – carbon cycle models. The study from the Hadley Centre group showed a very large positive feedback, atmospheric CO2 reaching 980 ppmv by 2100 if future climate impacts on the carbon cycle, but only about 700 ppmv if the carbon cycle is included but assumed to be insensitive to the climate change. The IPSL coupled climate – carbon cycle model simulated a much smaller positive feedback: climate impact on the carbon cycle leads by 2100 to an addition of less than 100 ppmv in the atmosphere. Here we perform a detailed feedback analysis to show that such differences are due to two key processes that are still poorly constrained in these coupled models: first Southern Ocean circulation, which primarily controls the geochemical uptake of CO2, and second vegetation and soil carbon response to global warming. Our analytical analysis reproduces remarkably the results obtained by the fully coupled models. Also it allows us to identify that, amongst the two processes mentioned above, the latter (the land response to global warming) is the one that essentially explains the differences between the IPSL and the Hadley results.