Climate economists widely acknowledge that there are only four policy levers that can be used in an attempt to lower carbon emissions and rein in climate change: reducing the world’s population, shrinking the global economy, increasing the efficiency of energy consumption, and decreasing carbon intensity (meaning that we create less carbon for each unit of energy that we produce).
事实上，气候经济学家们普遍承认，在降低碳排放并阻止气候变化方面只有四个政策杠杆可供利用：一是减少世界人口；二是收缩世界经济；三是提高能源使用效率；四是降低碳集中度（就是在每生产一个单位的能源时减少相应产生的碳）。