Climate change is a highly complex policy challenge. Its causes cut across all economic sectors. Solutions require many different kind of policy in energy, infrastructure, finance and innovation, to name just a few. At the international level, the United Nations Framework Convention on Climate Change (UNFCCC) is widely seen as the central pillar of a broader 'regime complex' , encompassing a number of formal and informal international policy processes. Negotiations on a new climate agreement should be concluded under the UNFCCC by the end of 2015. Many countries expect these negotiations to produce a durable and dynamic legal agreement, which can structure climate cooperation in the long-term. This raises the question: what can the new agreement do in order to better promote effective synergies within the different elements of the climate regime, and to manage potential frictions? This is the subject of this policy brief. The issue of regime fragmentation has gained more weight in recent times, as researchers and policy makers realise the complexity of climate change, and search for effective solutions. We can highlight four central reasons why the climate regime displays this degree of fragmentation: Ţ "TNFOUJPOFEBCPWF DMJNBUFDIBOHFJTBIJHIMZDPNQMFY NVMUJTFDUPS NVMUJTDBMFQSPCMFN"EESFTTJOHJUFƋFDUJWFMZSFRVJSFTDPPSEJOBUFEQPMJDZSFTQPOTFT JONBOZEPNBJOTPOHPJOHXPSLCZUIF0&$% GPSFYBNQMF BTTFTTFTUIFNVMUJQMFQPMJDZSFTQPOTFSFRVJSFEBUUIFOBUJPOBMMFWFMGSPNEJƋFSFOUTFDUPSBMQPMJDZQSPDFTTFT from energy policy, trade and competition policy, innovation policy, infrastructure planning, and financial regulation. The same principle holds at the international level. "