Tornadoes and climate change

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”.

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6 Responses to “Tornadoes and climate change”

  1. Kofi Renner Says:

    Very good piece. So we are looking at hopefully reducing greenhouse gases that will possibly slow down the rate of climate change and the extent to which tornadoes occur. Again climate change models could be improved so that they incorporate data on natural disasters like tornadoes. Hopefully we should see a trend. Again it is nature and if history serves us right, then climate change is somewhat natural, bound to happen, BUT it seems at a faster rate, because of mans will to explore and dominate the earth. Sixth extinction on my mind, but that is another kettle of fish.

    • andyrussell Says:

      Thanks for the comment, Kofi.

      Unfornately “making climate models better” is not straightforward. Even without improving the physics etc. you’d ideally want to increase the resolution (maybe from ~250km to 1-10km, which still wouldn’t resolve tornadoes!) and run large ensembles to account for the uncertainty. But this would cost an absolute fortune in computing time. So you need to try and be a bit more clever with the models that we can run.

      Perhaps, though, the tornadoes and climate change question is just to much for any computer model to handle?

      Ta

      Andy

  2. omnologos Says:

    One thing I realised with the Moore tragedy is how completely unadapted we still are…

    • andyrussell Says:

      I agree. I think it’s particularly relevant in regions that are poorly developed anyway, which often have the most uncertainty associated with climate projections. I don’t think that the climate change adaptation community makes the distinction between development and adaptation in these regions.

  3. PhilCollins_UK Says:

    Reblogged this on PalaeoMud and commented:
    Andy Russell has posted a thoughtful piece about tornadoes and climate change, following the tragic event in Oklahoma. It’s always going to be different to put the blame (or not) for individual extreme weather events onto climate change. Indeed, research into ‘palaeotempestology’ (the study of past storms, mainly using geological features) indicates that extreme events are actually a normal part of the Earth’s weather. One of the limitations of palaeotempestology research is that only the largest events have a chance of leaving a strong geological signature, and this may be localised (see the work by Kam-Biu Liu e.g. http://hol.sagepub.com/content/15/7/965). Often, the sedimentary signature of an extreme storm is similar to the results of other processes e.g. tsunami or deforestation).
    This all means that there is uncertainty over whether we are really experiencing more extremes than in the past. We do, however, know that the composition of the atmosphere has changed over the past few decades (recently passing the 400ppm CO2 level). That must impact on heat storage and distribution, and the precautionary principal appraoch to risk evaluation means we really should be planning infrastructure such as schools and medical centres in the expectation that they are likely to have to resist extreme events during their lifetimes.

  4. Another Week of Anthropocene Antics, May 26, 2013 – A Few Things Ill Considered Says:

    […] 2013/05/21: ARussell: Tornadoes and climate change […]

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