Without resolute counteraction, climate change will overstretch many societies' adaptive capacities within the coming decades. This could result in destabilization and violence, jeopardizing national and international security to a new degree. However, climate change could also unite the international community. This is provided that we recognize climate change as a threat to humankind and so set the course for adopting a dynamic and globally coordinated climate policy. If we fail to do so, climate change will draw ever-deeper lines of division and conflict in international relations, triggering numerous conflicts between and within countries over the distribution of resources - especially water and land, and over the management of migration, or over compensation payments between the countries mainly responsible for climate change and those countries most affected by its destructive effects. With Climate Change as a Security Risk, WBGU has compiled a flagship report on an issue that quite rightly is rising rapidly up the international political agenda. The authors pull no punches on the likelihood of increasing tensions and conflicts in a climatically constrained world and spotlight places where possible conflicts may flare up in the 21st century unless climate change is checked. The report makes it clear that climate policy is preventative security policy.