Climate change affects, and is affected by, all economic and social sectors. The UN system supports a wide variety of national efforts to reduce GHG emissions and adapt to climate change. While UN agencies and programmes pursue many activities within their own mandates, increasingly they combine their respective expertise to support cross-cutting initiatives. These joint efforts are also increasingly underpinned by the ability of Governments and UN organizations to leverage the new international climate institutions launched under UNFCCC. These mechanisms promote financing, technology, adaptation, emissions reductions, capacity-building and more. For example, the Convention’s Clean Development Mechanism, the first international system to boost investment in developing-country projects for reducing emissions at low cost, has become a model for how to encourage innovative climate solutions. This includes solutions that engage civil society, provide co-benefits and stimulate sustainable development. Some of the many ways in which the UN supports climate action can be illustrated through a few examples from some key sectors.