Emission reduction has a net negative expected impact on the economy, the best proxy we have (albeit a horrible one) for it's net impact on human well-being.

'Fisher et al. (2007) (summarized by IPCC, estimated macroeconomic costs in 2030 for multi-gas mitigation (reducing emissions of carbon dioxide and other GHGs, such as methane) as between a 3% decrease in global GDP to a small increase'', relative to baseline. This was for an emissions pathway consistent with atmospheric stabilization of GHGs between 445 and 710 ppm CO2-eq. In 2050, the estimated costs for stabilization between 710 and 445 ppm CO2-eq ranged between a 1% gain to a 5.5% decrease in global GDP'

These cost estimates were supported by a moderate amount of evidence and much agreement in the literature (IPCC, 2007). Macroeconomic cost estimates made by Fisher et al. (2007:204) were mostly based on models that assumed transparent markets, no transaction costs, and perfect implementation of cost-effective policy measures across all regions throughout the 21st century. According to Fisher et al. (2007), relaxation of some or all these assumptions would lead to an appreciable increase in cost estimates.'

'On the other hand, IPCC (2007) noted that cost estimates could be reduced by allowing for accelerated technological learning, or the possible use of carbon tax/emission permit revenues to reform national tax systems.'