试论本世纪末全球实现二氧化碳“净零排放”的难度

No Rosy Picture for Net-zero Emissions Goal by Century End

《巴黎协议》确认要将全球平均气温较工业化前水平升高幅度控制在2℃内,争取低于1.5℃,本世纪末实现二氧化碳＂净零排放＂。经分析,要实现该目标难度非常大,主要原因是：《巴黎协议》实现目标的措施不具体,依靠各国自主贡献的碳排放量总和远大于实现温升目标的碳排放限额,与科学家的判断和预测相距甚远;发展中国家在中远期还需要使用相当份额的化石能源,由于缺乏丰富的可再生资源,本世纪末仅中国每年就至少还要使用十几亿吨煤炭,实现净零排放难度相当大;发达国家已经跨过了碳排放峰值,而发展中国家碳排放峰值年不可能提前到2020年,要延后到2030~2040年,其后还有几十年的平台期或准平台期;发展中国家尤其是中国2050年非化石能源的替代份额已相当可观,已占到一次能源消费总量的32.2%（基本情景）和43.0%（积极情景）;本世纪末化石燃料燃烧、水泥生产、土地利用改变对大气中二氧化碳累积量增加的正贡献仍然大于土地吸收和海洋吸收的负贡献;CCS封存量有限,花费相当大的建设成本只封存几百万到几千万吨二氧化碳对减少温室气体排放起不到根本性的作用。

The Paris climate treaty aims to cap global warming at two Celsius degrees compared with pre-in-dustrial levels,with a target of 1.5 degree rise in the best scenario.These targets mean the world will need to achieve net-zero carbon emissions by the end of this century.Analysis shows these targets are really diffi-cult to achieve,due to the following ：the Paris treaty did not set out specific measures to achieve these goals and the total carbon emissions by countries are far higher than these countries ′ carbon emission reduction targets in order to arrest climate warming and also a far cry from scientists ′ judgments and predictions;de veloping countries still have to rely on fossil fuels to great extent in the long and medium term（due to a lack of abundant renewable resources,China will have to use at least more than one billion tons of coal yearly by the end of this century）,meaning it is very difficult to achieve net-zero emissions;the developed world has passed the peak of carbon emissions but the developing world ′ s peak of carbon emissions is unlikely to appear in advance in the 2020s（it should appear in 2030-2040 and a plateau or quasi-plateau lasting for decades will follow;use of a substantial amount of non-fossil fuel has already been under way or planned by2050 in developing countries,particularly China,which represent 32.2%（in basic scenario） or 43.0%（in aggressive scenario） of primary energy consumption;the increase in cumulative carbon dioxide volume in the air contributed by fossil fuel burning,cement production and land use remains higher than the volume of carbon dioxide absorbed by land and oceans;and the volume of carbon dioxide captured and stored is limited（storage of millions or tens of millions of tons of carbon dioxide,at a very high cost,does not have a substantial effect on greenhouse gas emission reductions）.