Monday, February 23, 2009

Gambling with climate change: MIT updates its climate gamble wheels

Back in 2001, MIT released its climate gamble wheels to indicate the risks and probabilities of climate change. It is based on the idea of a roulette wheel - we may know the odds, but we do not know where the 'ball' will stop. The odds are based on estimates from the latest research (see: Sokolov 2009) and therefore the wheels need to updated to indicate the latest information on the predicted odds and the chance of avoiding the possible effects of a greater than 2 degrees C increase in temperature. Figure 1 shows the updated wheel odds (with-policy designed to limit GHG emissions in place). The latest wheel suggests a change of temperature less than 2 degees C has odds of 1 in 5 (or 20% chance).

Figure 1: Updated with-policy climate wheel.

Compare this with the 2001 with-policy wheel (figure 2) below. Note that more than 3/4 of the wheel was considered 'safe' area to land on (with-policy) back in 2001.

Figure 2: 2001 with-policy climate wheel.

Now have a look at the updated no-policy wheel (figure 3). This is where we see a real decrease in the chances of temperatures staying below 3 degrees C. Hitting the blue area has odds of 100 to 1 (or 1% chance) of staying below 3 degrees rather than even 2 degees. I am sure that I don't want to play that game, with the 'future' at stake.

Figure 3: Updated no-policy climate wheel.

Finally, have a look at the 2001 no-policy climate wheel (figure 4) and notice how our chances of avoiding temperature increases of less than 2 degrees was seen as much higher compared to the updated wheel. In the new wheel the likelihood of exceeding 5°C is 57%, whereas in the 2001 wheel it was only about 4%. (That does not sound good!) The researchers explained the reason for this large increase in risk as follows (note: I have bolded the good bits):

"There is no single revision that is responsible for this change. In our more recent global model simulatations, the ocean heat-uptake is slower than previously estimated, the ocean uptake of carbon is weaker, feedbacks from the land system as temperature rises are stronger, cumulative emissions of greenhouse gases over the century are higher, and offsetting cooling from aerosol emissions is lower. No one of these effects is very strong on its own, and even adding each separately together would not fully explain the higher temperatures. Rather than interacting additively, these different affects appear to interact multiplicatively, with feedbacks among the contributing factors, leading to the surprisingly large increase in the chance of much higher temperatures."

Figure 4: 2001 no-policy climate wheel

So, for all those gamblers out there - can you now see why it is so important to have effective GHG emission policy in place? If we are to increase our odds of avoiding the worst of climate change we need effective policy. Plenty of people are willing "to take a punt" and "hope for the best", but should we even be happy trying to win a game with odds of says 1 in 2 ? Would you put your life savings on a coin flip? What if it was everyone's money and futures at stake? We certainly don't want to risk it all on a sweepstakes ticket with 100 entries because there is a much lower chances of sucessfully avoiding the worst of climate change.

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