The U.N.’s Intergovernmental Panel on Climate Change said that efforts to stabilize levels of greenhouse-gas emissions would require investments of about $13 trillion through 2030. It also noted that reducing emissions would reduce the rate of economic growth (as a result of such factors as higher energy prices). But it would do so by, on average, less than a tenth of a percentage point per year between now and 2100.
Switching from fossil fuels to low-carbon sources of energy will cost $44 trillion between now and 2050.
Aside from delays in action, many other factors will increase costs. Costs will go up if countries don’t all work together. They’ll also increase if technologies don’t work as expected. The most glaring example has to do with technology for capturing and storing carbon dioxide. According to the IPCC, if this technology can’t be deployed, the cost of stabilizing greenhouse-gas levels will more than double.
$13 trillion to try to stop the increase in CO2 production by 2020 and then get it back from 40 billion tons per year to 30 billion tons per year. 100 billion tons of CO2 avoided by 2030 for a cost of about $130 per ton.
Nextbigfuture has written that avoiding soot and particulates is cheaper and faster. Soot and particulate production would also save money by reducing lives lost and health impacts from particulates. About 2 million air pollution deaths per year could be avoided by eliminating 90% of particulate air pollution.