Regardless of whether the Paris Agreement achieves its full ambition or not, it will very likely result in progressively more stringent climate policy in most of the world’s economies. These policies will both affect trade directly and interact with the legal regime governing trade. This issue of UNCTAD's Commonwealth Trade Hot Topics reviews the outcome of COP21, analyses some of its possible impacts on trade, and then considers the implications specifically for small island developing states (SIDS), a group vulnerable to changes to climate and trade.