Is a particular weather event—such as a tornado outbreak or a record heat wave—caused by natural variability or global warming? There are no definitive answers yet, but scientists are beginning to provide insight into the effect climate change might have on the chances of an extreme event occurring.

Using computer models and sophisticated statistical techniques, researchers in the field of attribution science are able to estimate the odds that global warming increased (or decreased) the chances for certain extreme events.

The science of attributing extreme water and weather events to climate variability and change is relatively new. Several recent case studies have shed light on unusual events such as the 2003 European heat wave and the 2010 Russian heat wave. And, as seen in this image, some scientists are even producing forecasts of the changes in the odds of occurrence for hotter, colder, wetter, and drier events.

In the case of the 2010 Russian heat wave, researchers found the magnitude of that event was primarily caused by natural factors. Other scientists, who used a different approach, found that the risk of these types of events in western Russia has increased greatly due to global warming. It appears that, even if natural factors were the main cause of this particular weather extreme, the added strength produced by climate change pushed it to a new and dangerous level.

These early studies show promise, but much more work needs to be done to expand the regional areas and the types of weather events for which these studies are conducted. Researchers hope that improvements in attribution techniques will eventually lead to developing improved early warning capabilities.