Until fairly recent times no one thought climate changed, let alone was influenced by human activities. By the 19th century, scientists were theorizing that temperatures were affected by what we now call greenhouse gasses. And in the late 19th century, the Swedish scientist Arrhenius suggested that human industry might cause the planet to warm. But this notion was generally scoffed at. Over the course of the 20th century, the scientific community gradually came to terms with this theory and began to regard climate change—even rapid climate change—as more than a distant possibility. Interest in climate change as a national security issue developed even later. Although the Central Intelligence Agency (CIA) did commission a study to look into the security implications of climate change in the late 1970s, the issue had little resonance until the late 1990s when the Senate Armed Services Committee declared that environmental destruction, including global warming, was “a growing national security threat.” The Intergovernmental Panel on Climate Change (IPCC) was created in 1995 in part to allay fears. And then, in 2003, the rather notorious report commissioned by the Pentagon, “An Abrupt Climate Change Scenario and its Implications for United States National Security,” provided a worst-case scenario, which suggested that climate change might have a catastrophic impact, leading to rioting and nuclear war.1