Observationally-constrained climate projections following the Paris Agreement

最近生效的《巴黎协定》要求签署国“将全球平均气温的升幅控制在比工业化前水平高出2°C以下，并努力将气温升幅控制在比工业化前水平高出1.5°C以下”。由于二氧化碳是主要的温室气体，并且由于一定总量的二氧化碳排放产生相同的变暖量，无论它是一次性排放还是长期排放，1.5°C的变暖阈值可以与特定的二氧化碳排放总量或碳预算相关联。了解二氧化碳的最大排放量，同时有很大的机会将全球平均温度限制在1.5°C和2.0°C阈值以下，这是规划气候减缓战略和履行巴黎协定承诺的关键。

The Paris Agreement, which recently came into force, commits signatories to ‘holding the increase in global average temperature to well below 2°C above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5°C above pre-industrial levels’. Since carbon dioxide is the dominant greenhouse gas, and since a certain total amount of carbon dioxide emissions gives the same amount of warming irrespective of whether it is emitted all at once or over a long period, a warming threshold of 1.5°C can be associated with a particular total amount of carbon dioxide emissions, or carbon budget. Knowing the maximum amount of carbon dioxide which can be emitted while having a good chance of limiting global mean temperature to below the 1.5°C and 2.0°C thresholds is key to planning climate mitigation strategies and fulfilling the commitments made in the Paris Agreement.