Grist has discussed the consensus among most economists that the net cost of solving the climate crisis will be around 1 percent of gross domestic product (GDP). Basically this consensus says that total expenditures in various greenhouse gas emitting sectors will increase by 1 percent for the same economic output if emissions are controlled.
To be fair to economists, these estimates are based on studies that include substantial increases in energy efficiency -- even count some of the maintenance and capital savings. They are actually taking a stab at following Amory Lovins' dictum to count all costs and benefits.
Nonetheless, I think there are some good reasons why the consensus is wrong about there being a net cost at all. I think the overwhelming evidence is that a climate-stable future will have a higher GDP, even before avoided climate disruption is counted.
The main extra benefits economists overlook are the helpful side effects other than mitigating the climate crisis -- "positive externalities," in economic jargon.
For example, about half of all economic activity takes place in climate-conditioned buildings. Greening these buildings could increase[PDF] productivity [PDF] by around 10 percent. Similarly, switching most long-haul freight trucking miles to long-haul freight rail would increase productivity in transportation. Many energy-saving practices in industry, such as reducing scrapping and reducing spills and other types of emitting stoppages, would increase productivity as well. A switch to wind and solar would reduce labor productivity in the electricity sector; the conventional wisdom is that a switch to organic agriculture would do the same in that sector, though I think this is much less certain that people think. At any rate, sectors where productivity would rise greatly outnumber the tiny sectors where it might fall -- resulting in a huge net increase, probably greater than 5 percent for the economy as a whole.
Another example would be huge benefits to health. Eliminating or greatly reducing the use of fossil fuels would reduce air pollution, water pollution, and exposure to toxics. A switch to organic and low input agriculture would decrease direct ingestion of toxics, and increase available vitamins and minerals in food. Whether such a switch alone would encourage a switch to healthy increase in the consumption of non-starchy vegetables and fresh fruits I don't know, but it certainly could be part of policy that accomplished this. Overall, I think it is almost impossible that switching from fossil fuels to renewables and efficiency, that switching from toxic soil-consuming agriculture to non-toxic soil building agriculture, from unsustainable to sustainable forestry, would not increase GDP.
Two last points.