Research press release

気候感度の調節 (N&V)

Nature Climate Change

Climate sensitivity adjustment (N&V)



Drew Shindellは最新の気候モデル相互比較研究(CMIP5)の結果を分析し、気候感度が大気組成によってどのように変化するのかを解明した。単純なモデルを用いたこれまでの研究では、二酸化炭素に適用したのと同じ感度の重みづけを大気中の微粒子物質とオゾンにも適用しており、最近のある研究では、過渡気候応答(決められた期間内での気温の変化)は1.3℃であると報告されている。しかし、Shindellは微粒子物質やオゾン、二酸化炭素のさまざまな影響を考慮に入れることで、過渡気候応答は1.7℃になると報告した。これは、より複雑なモデルの結果と一致する。

David Stainforthはこのテーマと関連したNews and Viewsで、「過渡気候応答に関する今回の新たな推定値は、単純な気候モデルを適用する際の一般的な暗黙の了解に疑問を投げかけることで生じた」とし、単純なモデルは政策に関する研究で広く用いられているため、気温の変化を正確に予測することが重要だと指摘している。

The previous low-end calculations of climate sensitivity (temperature response to the changes in atmospheric composition) of less than 1.3 degrees Celsius are likely incorrect, reports a paper published online in Nature Climate Change. The reason for this low estimate is that calculations of climate sensitivity did not account for the greater net cooling effect of atmospheric particles and ozone as opposed to the warming effect of carbon dioxide.

Understanding how climate sensitivity is affected by changes in atmospheric composition is important for accurate projections of temperature changes resulting from anthropogenic emissions. However, despite increasing greenhouse gases, surface temperatures have increased relatively slowly over the past 10-15 years, leading to estimates of climate sensitivity based on those observations and simple climate models that were at the low-end of projections from complex climate models.

Drew Shindell analysed results from the latest climate model intercomparison study (CMIP5) to understand how climate sensitivity varies depending on atmospheric composition. Previous studies using simple models have applied the same sensitivity weighting to atmospheric particles and ozone as applied to carbon dioxide, and a recent study reported a transient climate response of 1.3 degrees Celsius. However, by taking into account the varying effects of particles, ozone and carbon dioxide, Shindell reports a transient climate response of 1.7 degrees Celsius. This is in line with more complex model results.

In an accompanying News and Views piece, David Stainforth writes, “this new estimate for transient climate response comes about by questioning a widely-made implicit assumption in the application of simple climate models” and notes that it is important for simple models to accurately project temperature changes as they are the models commonly used for policy-relevant research.

doi: 10.1038/nclimate2136


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