In a Sept. 21 memo to his department heads, President Obama instructed all federal departments and agencies to consider the impact of climate change on national security. Obama states that it is the policy of the U.S. government to ensure that current and anticipated impacts of climate change be "identified and considered" in developing national security doctrine, policies and plans. "Climate change poses a significant and growing threat to national security, both at home and abroad," the memo says. Those threats, according to Obama, include flooding, drought, heat waves, intense precipitation, pest outbreaks, disease, and electricity problems, all of which...