Tornadoes and Climate Change

The link between tornadoes and climate change is currently unclear. Current data on tornadoes is inconsistent because measuring the presence of tornadoes relies on eyewitness accounts and aftermath damage assessments rather than quantifiable data. Additionally, it is difficult to identify long-term trends in tornado records, which only date back to the 1950s in the U.S., because the population in many areas affected by tornadoes has grown, contributing to increased eyewitness reports and greater property in harm’s way. Improved technology, such as advanced radar, also helps us “see” tornadoes that may not have been detected decades ago.

An additional challenge is the physics associated with tornadoes. Researchers are working to better understand how the building blocks for tornadoes – atmospheric instability and wind shear – will respond to global warming. It is likely that a warmer, more humid world would allow for more frequent instability. However, it is also possible that a warmer world would lessen chances for wind shear. Climate change also could shift the timing of the tornadoes or the regions that are most likely to be hit, with less of an impact on the total number of tornadoes.

An added difficulty in trying to determine future tornado frequency and intensity based on changes in the climate, is that tornadoes are too geographically small to be well simulated by climate models. Models can simulate some of the conditions that contribute to forming severe thunderstorms that often spawn tornadoes. Multiple studies find that the conditions that produce the most severe thunderstorms are more likely in a warmer world.

It will remain challenging to estimate any climate change influence on tornadoes until scientists can improve their physical understanding of the processes that cause tornadoes and the observational record of tornado frequency.

 

Tornado Activity in the United States (1955-2013)

Relative Confidence in Attribution of Different Extreme Events

Threats posed by tornadoes

The most significant threats from tornadoes are the dangers posed by strong winds and debris that is caught up in those winds. Although individual tornadoes may affect a relatively small area compared to large tropical storms, they can threaten people, homes, and communities. NOAA estimates that, on average, about 1,200 tornadoes occur across the country annually, but several hundred more or fewer tornadoes can occur in any given year.

The death toll from tornadoes has dropped rapidly because forecasters have more tools to detect dangerous weather and warn people to take shelter. However, tornadoes still cause billions of dollars of property damage a year. The costliest year on record for tornado damage was 2011, when seven tornado and severe weather outbreaks each caused more than $1 billion in damages, and the total damage for the year was more than $28 billion.

How to Build Resilience

Communities can bolster their resilience and reduce the impacts from tornadoes by:

  • Adopting more stringent building codes in tornado-prone areas.
  • Continuing to support research on severe weather forecasts.
  • Heeding watches and warnings when they are issued, and ensuring that individuals can be reached by emergency alert systems.

Annual Average Number of Tornadoes Per State (1985-2014)