Top-down climate negotiations embodied by the Kyoto Protocol have all but stalled, chiefly because of disagreements over targets and objections to financial transfers. To avoid those problems, many have shifted their focus to linkage of bottom-up climate policies such as regional carbon markets.

On 31 March, the Intergovernmental Panel on Climate Change (IPCC) released its latest report on the impacts of climate change on humans and ecosystems (see go.nature.com/ad5v1b). These are real risks that need to be accounted for in planning for adaptation and mitigation. Pricing the risks with integrated models of physics and economics lets their costs be compared to those of limiting climate change or investing in greater resilience.

International and domestic efforts to reduce greenhouse gas emissions require a coordinated effort from countries and individuals that differ in terms of their level of income, historical responsibility in terms of contributions to the existing stock of emissions, current intensity of energy use and costs of reducing emissions. This brief reports the results of an economic experiment that examines whether groups of individuals – who differ in terms of their individual costs of reducing emissions – can meet a collective emissions reduction target.

The introduction of a price on CO2 is expected to be more efficient than prescriptive regulation. It also instantiates substantial economic value. Initially, programs allocated this value to incumbent firms (grandfathering), but the growing movement toward auctioning or emissions fees makes carbon revenues into a payment for environmental services. This paper asks to whom should this payment accrue?