Climate change as a national security issue

to do an analysis of just how unusual the recent weather has been, based on the longest historical database we have,” McElroy said. “The net conclusion is that weather is changing dramatically in specific regions, and the nature of the change is that we’re seeing more record high temperatures and many, many fewer low-temperature records.”

Other potential effects, McElroy said, are tied to changes in an atmospheric circulation pattern called the Hadley circulation, in which warm tropical air rises, resulting in tropical rains. As the air moves to higher latitudes, it descends, causing the now-dry air to heat up. Regions where the hot, dry air returns to the surface are typically dominated by desert.

The problem, he said, is that evidence shows those arid regions are expanding.

“The observational data suggest that the Hadley circulation has expanded by several degrees in latitude,” McElroy said. “That’s a big deal, because if you shift where deserts are by just a few degrees, you’re talking about moving the southwestern desert into the grain-producing region of the country, or moving the Sahara into southern Europe.”

The report is the result of the authors’ involvement with Medea, a group of scientists who support the U.S. government by examining declassified national security data useful for scientific inquiry. In recent decades, the group has worked with officials in the United States and Russia to declassify data on climatic conditions in the Arctic and thousands of spy satellite images. Those images have been used to study ancient settlement patterns in the Middle East and changes in Arctic ice.

“I would be reluctant to say that our report is the last word on short-term climate change,” McElroy said.

“Climate change is a moving target. We’ve done an honest, useful assessment of the state of play today, but we will need more information and more hard work to get it right. One of the recommendations in our report is the need for a serious investment in measurement and observation. It’s really important to keep doing that, otherwise we’re going to be flying blind.”

“The bottom line is that our national security depends on our ability to sustain and augment our scientific and technical capacity to monitor unfolding events and forewarn of important changes,” Baker said. “The imminent increase in extreme events will affect water availability, energy use, food distribution, and critical infrastructure — all elements of both domestic and international security.”

The study was conducted with funds provided by the Central Intelligence Agency. Any opinions, findings, conclusions, or recommendations expressed in this material are those of the authors and do not necessarily reflect the view of the CIA or the U.S. government.

 — Read more in Michael McElroy and D. James Baker, Climate Extremes: Recent Trends with Implications for National Security (Harvard University, October 2012)

This story is published courtesy of the Harvard Gazette, Harvard University’s official newspaper.