Following the chaotic Copenhagen conference of the UN Framework Convention on Climate Change (UNFCCC), policymakers and pundits have discussed the G-20 as an alternative forum for advancing climate change diplomacy. This paper assesses the risks and rewards of tackling climate change in the G-20 and finds that despite its seeming attractiveness, the G-20, as structured, is not a suitable replacement for the UN-led process and has limited ability, at present, to advance climate change negotiations. There is much, however, that the G-20 can do to contribute to the goals of the climate negotiations outside of wading into the negotiations themselves. Building on its existing agenda the G-20 has the power to significantly reduce global greenhouse gas emissions, accelerate the deployment of clean energy technology, and help vulnerable countries adapt to a warmer world through the mobilization of public and private finance. Following through on the existing G-20 pledge to phase out and rationalize inefficient fossil fuel subsidies, establishing new green guidelines for multilateral development banks, coordinating green stimulus exit strategies, promoting open markets for environmental goods and services, and rebalancing global economic growth all fall well within the G-20's mandate and help meet the climate challenge.