But the study also finds that strikes carried out by unmanned aerial vehicles cause fewer civilian casualties than other kinds of combat and that those deaths don't appear to be linked to further violence against U.S. forces and allies.
A Global Hawk unmanned aircraft comes in for a landing at the Wallops Flight Facility in Wallops Island, Va., on Sept. 7, 2012, after studying Hurricane Leslie. The remotely controlled planes can stay in the air for as long as 28 hours and fly over hurricanes at altitudes of more than 60,000 feet.
For several weeks now, two unmanned spy planes have been flying over the Atlantic on an unusual mission: gathering intelligence about tropical storms and hurricanes.
The two Global Hawk drones are a central part of NASA's five-year HS3 (Hurricane and Severe Storm Sentinel) Mission investigating why certain weather patterns become hurricanes, and why some hurricanes grow into monster storms.
Protesters in Pakistan shout anti-U.S. slogans during a protest in July against drone strikes in Pakistan's tribal areas.
Credit Arif Ali / AFP/Getty Images
A senior leader of the al-Qaida-linked Haqqani network — considered one of the most dangerous factions fighting American troops in Afghanistan — has been killed in a U.S. drone strike over northwestern Pakistan, officials say.
Sangeen Zadran was among five people killed at a compound in the North Waziristan tribal region when a missile fired from a U.S. drone hit the building, Pakistani intelligence officials said.
Oklahoma was hit particularly hard by two massive outbreaks this year in what's been another deadly season of tornadoes in the U.S. Despite technology and forecasting improvements, scientists still have plenty to learn about how and why tornadoes form.
Currently, one of the best ways for researchers to understand how tornadoes form is to chase them. So off they go with mobile science laboratories, rushing toward storms armed with research equipment and weather-sensing probes.