A common argument against acting on climate change now is that doing so would cost money—a lot of it. A new report, timed to coincide with the United Nations Climate Summit next week, says the conventional thinking is wrong. 

Commissioned by seven countries in the Global Commission on the Economy and Climate, the report notes that the countries of the world are going to have to spend $90 trillion over the next 15 years upgrading infrastructure—replacing old roads and power plants, building new sewage and electrical systems. If the countries of the world decided to curb greenhouse gas emissions in the process, the report says, that would tack on just $4 trillion more—i.e., not a lot of money, relatively speaking. 

And that’s before taking into account the costs imposed by letting climate change continue at its current pace. 

This chart below, from the report, helps to quantify that. Improvements in energy efficiency and clean energy cut back on heat-trapping gasses, but they also mean less air pollution. Air pollution, specifically fine particulate matter called PM 2.5, is linked to millions of deaths globally each year. As you can imagine, the economic costs associated with these deaths are massive. According to the New Climate Economy's calculus, the 15 countries with the highest emissions saw health costs averaging 4 percent of GDP in 2010—dwarfing the extra costs of efforts at reducing climate change: