Wednesday, January 12, 2011

Bolt just doesn't get it.

Sadly Queensland is suffering a flood the like of which we haven't seen since 1974, and lives have been lost, to say nothing of property. Sadly, conservative commentator Andrew Bolt has used this as a pretext to bash global warming science yet again in his blog here.

He states "What I cannot understand is this: how was the possibility of such a danger not forseen, when climate experts and the Government claim they can predict the climate 100 years from now? How did this week’s rain come as such a surprise, when we now spend billions more on computer models predicting the future?"

I can't at this time comment on how well the situation was forecast since I haven't looked closely at the evolution, but a few comments are worth making.

Firstly, it is worth understanding that sometimes situations develop rapidly due to the right ingredients being there, and sometimes the information is not available to the models to simulate this rapid development. Oftentimes the human forecaster adds enormous value. Secondly, given that such an event is an extreme one, picking the precise values of rainfall can be beyond the models, however they can point to the fact that an event will be extreme.

Thirdly, there are comparisons with this event and the one in 1974 which was also a result of a La Nina year. A rearrangement of the ocean temperatures and wind patterns in the Pacific can result in floods during La Nina years and drought during El Nino years. Given this, we need to exercise caution in ascribing this event to global warming. Certainly under global warming there is more moisture contained in the atmosphere and hence an increased chance of more severe rainfall events (think the recent monsoon in Pakistan). This natural variability will continue, so while Bolt is right to point out that global warming scenarios have QLD receiving less rainfall on average, this does not mean that events like this are no longer possible.

Finally, the comparison of (sometimes) poor weather forecasts and climate projections is a false one. In the case of the former, a lack of evidence can lead to large errors in the forecast (think of chaos theory). This is known as an initial value problem as the initial measurements are key. The forecast problem is one of predicting accurately certain weather elements like wind speed and direction, rainfall amount at a point (in models averaged over a grid box) or maximum temperature. For climate projections, we are more interested in the mean conditions averaged over a larger grid box than a forecast model (due to computing and time constraints) and time, and not in precise values like the temperature at Melbourne on Feb 2, 2100. This kind of accuracy is impossible due to chaos. However, mean climate states and values like global mean temperatures or regional mean temperatures are possible. This is because the kind of forcings like solar output or greenhouse gases together with the state of the physical earth are more important than the effect of the state of the atmosphere now on the future climate.

It is a shame Bolt can't resist using a tragedy to highlight his willful ignorance of what should be plain to all. We can't say global warming has caused this event, though it may be consistent with it. All we should do is pray, lend a hand and a few dollars, showing the love of Christ to those in need.

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