The 2015 UN climate change conference in Paris (COP21) is a pivotal moment. Governments have set December 2015 as the deadline to agree on a new climate regime for 2020 onwards. This deal must give the world a ﬁghting chance to avoid dangerous global temperature rises. Such an agreement needs to be fair, ambitious, and transformational. At the same time, COP21 provides an opportunity to showcase efforts that countries, the private sector, and civil society are making to combat climate change – and to accelerate and scale up these actions.