A new report investigates the causes of extreme weather and climate events that occurred around the world in 2013, finding evidence for both human and natural influences.

New NASA research shows that Earth's atmosphere contains an unexpectedly large amount of carbon tetrachloride (CC14), an ozone -depleting chemical that was banned worldwide decades ago. According to the study, global emissions of CCl4 average 39 kilotons per year—approximately 30 percent of peak emissions prior to its banning.