The extreme weather, including a near-record number of tornadoes, in 2011 forced the debate of the impact of climate change on severe weather to resurface.
While there has been research into the subject, there are still many unknowns.
Is a Warming Climate Causing More Active Severe Weather Already?
Before examining how climate change may affect severe weather in the future, it is important to analyze whether the frequency or strength of severe weather has changed already with warming temperatures.
There is no strong evidence to support severe weather becoming stronger, more frequent or more widespread during the past 50 years in the United States as a result of climate change. One of the reasons that the change in severe weather is hard to track is the fact that the reporting systems have changed so much over time.
Ted Fujita developed the Fujita Scale, which measures the intensity of tornadoes by examining damage and estimated winds, in 1971. Meteorologists did not start rating twisters using the Fujita Scale until 1973.The National Oceanic and Atmospheric Administration (NOAA) went back through tornado reports from 1950 through 1972, retroactively rating tornadoes based on the damage information provided in the reports.
"Our best effort is to try to take care of those changes in reporting and indicate that we really haven't seen any changes [in severe weather]," Harold Brooks, Research Meteorologist at NOAA's National Severe Storms Laboratory in Norman, Okla., said.
However, with advancements in technology and social media, news of extreme and severe weather spread very quickly to all corners of the U.S.
"The big reason why we think that severe weather has gotten worse is our ability to communicate information about it. If you think back 100 years ago, a tornado that happened 10 or 20 miles away, you might not even be aware of it, if it didn't affect where you live directly. Now, you can watch people chasing tornadoes online live," Brooks explained. "So it's the fact that we are more aware and able to communicate that information about events so much better than we used to be able to that it makes us think severe weather has increased."
Future Climate Change Impacts on Severe Weather
There are still many limits to our knowledge of how severe weather will change as the climate warms, but some preliminary conclusions can be made from research so far.
Global Land-Ocean Temperature Index Graph from NASA's Goddard Institute for Space Studies.
"As the planet warms with more greenhouse gases, we really don't have very strong evidence as to what will happen with severe thunderstorms," Brooks said.