The purpose of this second Hamburg Climate Futures Outlook is to systematically analyze and assess the plausibility of certain well-defined climate futures based on present knowledge of social drivers and physical processes. In particular, we assess the plausibility of those climate futures that are envisioned by the 2015 Paris Agreement, namely holding global warming to well below 2°C and, if possible, to 1.5°C, relative to pre-industrial levels (UNFCCC 2015, Article 2 paragraph 1a). The world will have to reach a state of deep decarbonization by 2050 to be compliant with the 1.5°C goal. We therefore work with a climate future scenario that combines emissions and temperature goals.

The physical environment in which the U.S. Department of Defense (DoD) must operate is being affected by climate hazards, which adversely affect the performance of the joint force and the systems that support it. Generating, maintaining, and even increasing force readiness in light of changing climate threats is a key component of meeting high-level U.S. strategic goals, from defending the homeland to deterring aggression and strategic attacks. Acknowledging that climate effects are likely to become more severe as global temperatures rise, the authors of this report discuss the results of an initial study they conducted to develop links between climate and readiness, laying the groundwork for the eventual integration of climate risk with quantitative readiness assessment and decisionmaking to help ensure that military forces can reliably and affordably sustain needed readiness in a changing climate.