Thursday, 18 December 2008

Australia’s shameful response to climate change

When Kevin Rudd announced a 5% target for emissions reductions for 2020, you could almost hear John Howard laughing from the political grave. It's small comfort to me that in discussing climate matters since then, a Labor supporter called Rudd “Howard” by mistake. Freudian?

The science the government has in front of it says you have to reduce emissions by 25% by 2020 to save the Great Barrier Reef. Of course Australia cannot achieve this on its own because it accounts for a relatively small fraction of worldwide emissions – even if you account for its role as the world’s biggest exporter of coal (about a third of worldwide exports).

Another thing not widely talked about is that carbon emissions accumulate. Around half are absorbed by the environment; the rest dissipates very slowly over centuries. That means that if we have not achieved a target by 2020 that stops CO2 accumulating to 550 parts per million or more, we can’t just turn off the tap and expect the atmospheric CO2 level to drop.

How soon will the rest of the world regard carbon emissions as a serious, urgent problem? That Europe has committed to a 20% cut by 2020 is some indication.

Why should Europe care more? Partially, it’s because Europe has a stronger tradition than English-speaking countries of taking science seriously. But another factor is Europe’s proximity to the Arctic. A growing number of scientists is predicting an ice-free Arctic summer by 2015. It was a big enough shock when it was reported in 2007 that the Arctic could be ice-free in summer by 2030.

So in a sense the self-styled sceptics are right. The science has enough uncertainties that we have to be cautious about accepting predictions without a wide allowance for error. The problem is, the majority of cases that are breaking out of the modelled predictions are on the worse rather than the better side. How is this possible? With the vast bulk of “sceptics” accusing scientists who predict anything remotely bad of being “alarmist”, the natural tendency of scientists to avoid alarming claims without overwhelming evidence is accentuated. So work predicting rapid ice cap loss for example is not getting the attention it should. Another example: concerns about the possibility of the urban heat island effect (UHI) skewing the temperature trend has resulted in NASA compensating for this effect. While it is true that a temperature sensor put next to an isolated hot spot would be bad for once-off measurement, if that hot spot is not constantly being hotter, it would not add a trend to the stats.

NASA eliminates local anomalies by a process called homogenizing, where temperatures of each station are in effect corrected for excessive variation beyond others in similar terrain.

Let’s look at how over-estimating the effect of UHI could have on the temperature trend. If NASA weights down temperatures from urban area, they could be underestimating the general increase in temperatures, because some of these areas could naturally be heating faster than their surroundings.

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