On 12 November 2014, they jointly announced a plan to strengthen bilateral and multilateral co-operation on climate change, with the aim of adopting an ambitious climate agreement at the 2015 United Nations Climate Change Conference (COP21). The countries made national-level pledges: China promised to peak carbon emissions by 2030 and increase the share of non-fossil fuels in primary energy consumption to around 20% by 2030, while the United States vowed to achieve economy-wide emissions reductions of 26-28% below 2005 levels by 2025.3 If carbon pricing became an element of these pledges, the coverage of global greenhouse gas emissions would increase significantly. In the case of carbon taxes, recycling tax revenues back to consumers - e.g. by reducing income or business taxes and increasing budgetary allocations for social services -can help ease resistance to implementation. Nevertheless, carbon pricing remains politically challenging and is struggling to gain momentum in many parts of the world.