According to the Guardian:
The biggest single impact on the $2.2tn estimate, accounting for more than half of the total, was emissions of greenhouse gases blamed for climate change. Other major "costs" were local air pollution such as particulates, and the damage caused by the over-use and pollution of freshwater.
The true figure is likely to be even higher because the $2.2tn does not include damage caused by household and government consumption of goods and services, such as energy used to power appliances or waste; the "social impacts" such as the migration of people driven out of affected areas, or the long-term effects of any damage other than that from climate change. The final report will also include a higher total estimate which includes those long-term effects of problems such as toxic waste.
The report is based on data from Trucost, the company also responsible for Newsweek's rating of the 'Greenest Big Companies in America'.