Comment by gersh

There are about 37 billion tons of CO2 emissions per year. If you could get the price down to $100/ton, you can get the world net zero for $3.7t/year. US GDP is 25 trillion/year. World GPD is about 96.5 trillion. So, it would cost about 3.8% of world GDP per year. World global military is about $2.2t/year, so it would be higher than global military expenditure, but somewhat theoretically possible. If you substantially reduced emissions, it might be feasible to use carbon capture for the rest.