Professor Roger Pielke Jr. of the University of Colorado Boulder: "The world is presently in an era of unusually low weather disasters. This holds for the weather phenomena that have historically caused the most damage: tropical cyclones, floods, tornadoes and drought. Given how weather events have become politicized in debates over climate change, some find this hard to believe...The US has seen a decrease of about 20% in both hurricane frequency and intensity at landfall since 1900...Data on floods, drought and tornadoes are similar in that they show little to no indication of becoming more severe or frequent...Thus, it is fair to conclude that the costs of disasters worldwide is depressed because, as the global economy has grown, disaster costs have not grown at the same rate. Thus, disaster costs as a proportion of GDP have decreased. One important reason for this is a lack of increase in the weather events that cause disasters, most notably, tropical cyclones worldwide and especially hurricanes in the United States."