未來的氣候在過去的4.2億年中從未出現過

論文標題：Future climate forcing potentially without precedent in the last 420 million years

作者：Gavin L. Foster et al

數字識別碼：10.1038/ncomms14845

《自然-通訊》發表的Future climate forcing potentially without precedent in the last 420 million years報道稱，如果人類不減少化石能源的使用，地球系統將遭遇5億年來從未出現過的地質先例。

地球氣候在地質時標上的演變很大程度上取決於太陽總輻照度（TSI）和大氣中溫室氣體含量的變化。來自英國南安普頓大學的Gavin L. Foster及其同事發現，在過去的約4.2億年內，緩慢增加的約50 Wm-2 TSI（輻射強迫增加了約9 Wm-2）幾乎完全因大氣中二氧化碳濃度的長期下降所抵消。這可能是由於硅酸鹽風化的負面反饋和陸地植物的擴張共同確保了地球的長期宜居性。

如果人類不減少使用化石燃料，到二十一世紀中葉我們將面臨的風險是，二氧化碳將達到自始新世早期（5000萬年前）以來的最高值。如果二氧化碳繼續上升，到二十三世紀，與此相關的強迫輻射的大幅度增加，以及地球系統會如何反應，都將成為過去五億年間沒有出現過的地質先例。

摘要：The evolution of Earth』s climate on geological timescales is largely driven by variations in the magnitude of total solar irradiance (TSI) and changes in the greenhouse gas content of the atmosphere. Here we show that the slow ～50 Wm?2 increase in TSI over the last ～420 million years (an increase of ～9 Wm?2 of radiative forcing) was almost completely negated by a long-term decline in atmospheric CO2. This was likely due to the silicate weathering-negative feedback and the expansion of land plants that together ensured Earth』s long-term habitability. Humanity』s fossil-fuel use, if unabated, risks taking us, by the middle of the twenty-first century, to values of CO2 not seen since the early Eocene (50 million years ago). If CO2 continues to rise further into the twenty-third century, then the associated large increase in radiative forcing, and how the Earth system would respond, would likely be without geological precedent in the last half a billion years.

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