Archive for May, 2013

Tornadoes and climate change

May 21, 2013

I’m sure you’ve already seen the sad news about the tornado in Oklahoma – it looks like it has done a lot of damage and claimed a lot of lives.

Tornadoes are not uncommon in that area and it is almost impossible to make good forecasts of where they will hit as they are too small for computer forecast models to capture. Even the scientific understanding of how they form is not great as it’s really hard to get good measurements of them in their destructive phase.

I’m sure that the discussion will now turn to the role of climate change in this particular event but, as usual, that’s a very difficult question to ask despite recent efforts on this front. At one level it’s quite easy to speculate that if the warm air heading north from the Gulf of Mexico that fed the storm that spawned the tornado was warmer than it otherwise would have been then, yes: climate change could have made this event more likely and/or stronger.

But the atmosphere doesn’t really work like that and the number of complex factors required to produce any specific tornado makes the cause and effect arguments that are wrapped up in the  “link to climate change” question very, very difficult.

But perhaps we think about this more statistically and ask whether tornadoes will get stronger and/or more likely in a warmer future climate.

Again, this is really difficult because climate models certainly don’t have the power (i.e. high enough resolution) to represent tornadoes. So you can’t just go through climate model data and count the tornadoes that it thinks will occur.

If we think statistically again, though, we can look for the change in larger scale conditions that usually produce tornadoes.

Unfortunately, this isn’t particularly clear either.

Whilst the increased warmth and moisture predicted by climate models will mean more energy would be available to developing tornadoes, the climate projections also show a decrease in the occurrence of the wind patterns that are needed to form tornadoes.

Nonetheless, one thing that does seem likely is that we can still reduce the likelihood of a stormier future world. If you compare the storminess of climate simulations with, say, “medium” and “high” greenhouse gas concentrations (as done here) then the “medium” case looks better than the “high”.