In December 2015 over 190 countries met in Paris for the 21^st meeting of the United Nations Framework Convention on Climate Change where they succeeded in creating a new and ambitious international climate agreement.  Many have heralded the outcome as a groundbreaking achievement for international diplomacy and global climate action.  Others have argued that the climate commitments in it are ultimately too weak to achieve the agreements’ lofty aspirations.  To better understand the significance of the agreement, and why it is worth fighting for its preservation, we will review the recent history of the UN climate negotiations, and how this outcome evolved from earlier failed attempts in this process, finally overcoming the immense hurdle of justly assigning responsibility for hitting global emission reduction targets.  The Paris Agreement is now undergoing an unexpectedly early stress test with the announcement of the intended withdraw of the United States.  We conclude with a look at what the future holds for global climate cooperation in the face of this serious challenge, including indications of how different communities are prepared to defend the agreement and continue coordinated action on this increasingly urgent problem.