In the wake of extreme weather events, people often ask scientists if they can be linked to climate change. Naturally, questions are being asked about tornadoes following the tragic losses suffered in the region of Moore, Oklahoma on May 20, 2013 after an EF5 Tornado.
This historic force of nature was met by heroic stories of lives saved through quick actions by teachers and neighbors to help others seek shelter, which are important to be told in the immediate wake of tragedy. Nonetheless, questions are naturally being asked and stories told about this tornado and connections to climate change.
The short answer is that scientists don’t see a clear link between climate change and the number or intensity of tornadoes over the past several decades. The Intergovernmental Panel on Climate Change special report on extreme events expressed “low confidence,” mainly due to inadequacies in monitoring systems.
While a warmer planet could theoretically affect tornadoes, such as warmer and moister atmosphere, jet stream location changes, and equator to polar temperature gradient changes, we just don’t yet have enough data over the long-term to draw firm conclusions.
Tornadoes are rare, short-lived, and difficult to measure, and the record also has to account for a change in the tornado classification system. By contrast, scientists have many ways to measure and model heat waves, coastal flooding, and changes to precipitation patterns — and consequently have been able to draw definitive links between those phenomena and climate change.
Thankfully, collecting more data on tornadoes has many benefits, especially for people who live in areas at risk for them. In fact, people can report tornadoes directly to NOAA’s National Severe Storms Laboratory and University of Oklahoma through a smartphone once they are safely sheltered.
Better data collection can help further improve warning systems for tornadoes. Minutes matter. The extra few minutes of warning compared to historical tornado warnings are now possible with advances in National Weather Service monitoring and tracking. Extra minutes to get into a shelter can mean more lives saved in a “Weather-Ready Nation.”
Fast Facts about U.S. Tornado Trends
Our understanding of how a warmer planet affects storms that spawn tornadoes, as well as wind patterns, suggests more atmospheric energy could be available for tornado systems. On the other hand, tornadoes are difficult to model since specifics for individual tornado formation are still an area of active scientific research. Furthermore, tornadoes are tiny compared to the average grid spacing in most climate models.
Based on the data we have to date, there are no clear trends for tornado frequency or intensity. Tornado damage estimates depend in part on how many people and how much property is in its way.
The number of severe U.S. tornadoes EF3 or greater (those with gusts of greater than 136 miles per hour), has not changed much between 1954 and 2012. The most severe tornadoes, rated on damage, typically occur in KS, AR, TX, OK, TN and MO. As more people occupy areas affected by tornadoes, we have more potential damage, but we also have more eyes watching the sky and more ways to report and track tornadoes, resulting in more data than ever before.
Update May 24, 2013 in response to comment: Below is the figure for the annual count of US tornadoes EF1 or greater recorded in the US.
Feature image: NOAA