I recently made an earlier attempt at exploring probability in relation to climate.
The “loading the dice” analogy is becoming popular but it misses something very important: climate change also allows unprecedented (in human history) things to happen. It is more like painting an extra spot on each face of one of the dice, so that it goes from 2 to 7 instead of 1 to 6. This increases the odds of rolling 11 or 12, but also makes it possible to roll 13.
What happens then?
Since we have never had to cope with 13’s, this could prove far worse than simply loading the dice toward more 11’s and 12’s. I’m not sure whether or not what is happening in Russia or Pakistan is a “13” yet, but 13’s will eventually arrive (and so will 14’s, if carbon emissions continue to rise).
Michael thinks that we have just seen our first thirteen (or possibly our second if you count Australia’s experience in 2009).
He goes on to say
I can define a fourteen easily. We will have rolled a fourteen when there is no controversy at all about whether the given event was in the range of unforced natural variability.
I’m reluctant to argue with someone like Michael – but I guess it depends on how you define “controversy”.
NOAA have published a draft report on The Russian Heat Wave of 2010 (copied and pasted in its entirety by Watts. I do hope he asked for permission to do so).
NOAA point out that Moscow’s average July temperature was 4 standard deviations above the long-term climatology. Since you would expect 99.994% of data values in a normal distribution to fall within 4σ of the mean, calling this a 13 (unprecendented) seems reasonable. And the impact is huge. As Michael points out,
If we consider the Russia and Pakistan catastrophes as part of the same event, we have easily thirty million people directly affected and loss of life in the tens of thousands.
That is without taking crop losses in both countries into account, which is also likely to have a substantial impact.
But can we attribute it to climate change?
NOAA think not:
Despite this strong evidence for a warming planet, greenhouse gas forcing fails to explain the 2010 heat wave over western Russia. The natural process of atmospheric blocking, and the climate impacts induced by such blocking, are the principal cause for this heat wave. It is not known whether, or to what exent, greenhouse gas emissions may affect the frequency or intensity of blocking during summer. It is important to note that observations reveal no trend in a daily frequency of July blocking over the period since 1948, nor is there an appreciable trend in the absolute values of upper tropospheric summertime heights over western Russia for the period since 1900.
So that’s alright then, isn’t it?
NOAA think not:
The 2007 IPCC report highlights surface temperature projections for the period 2090-2099 under a business-as-ususal scenario that reveals +5°C to +7°C warming warming of annually average temperatures over much of Eurasia under an aggressive A2 scenario.
As we learn from our 2010 experience what a sustained heat wave of +5°C to+10°C implies for human health, water resources, and agricultural productivity, a more meaningful appreciation for the potential consequences of the projected climate changes will emerge. It is clear that the random occurrence of a summertime block in the presence of the projected changes in future surface temperature would produce heat waves materially more severe than the 2010 event.
I’d rather not wait for Michael’s 14 to be thrown – but even if the Mediterranean Sea boiled dry I’m sure we would still have inane comments like these at WUWT:
etc. etc. etc.
[ – Wikimedia
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