Climate change offers humanity no second chances. An agreement struck at the UN climate conference in Copenhagen in December 2009 could pave the way for a post-2012 climate regime that staves off catastrophic climate change. Delay or failure will certainly multiply the costs of responding to its negative impacts - costs that are already being borne by poor people. Rich countries must reduce greenhouse gas emissions first and fastest. But whilst deep emissions reductions in rich countries are still critical, climate security will now be won or lost as a result of co-operative efforts in which rich countries finance large-scale emissions reductions in developing countries. <br /><br /> Establishing a Global Mitigation and Finance Mechanism can achieve these reductions while respecting principles of equity and delivering tangible development gains for poor people. This must be a centrepiece of the Copenhagen deal.