How Much Will The Carbon Tax Affect Global Temperatures?

19 Oct

Every now and then, you see, in a comment thread, someone ask “by how much will Australia’s Carbon Tax reduce temperatures?”

I am presuming that the people who ask this question are skeptical that the tax will do any good. They think the answer is “zero”. It turns out it’s not.

However, the question is actually the wrong one to ask. Human beings, almost no matter where they live, are used to bearing with annual and even daily temperature changes of dozens of degrees. Global warming affects us indirectly. We don’t care much if the weather is 2 degrees hotter, but we care a great deal if a storm is stronger, if a river floods, if food prices go up or a business fails. The right question is “how much will the Carbon Tax affect things like the agricultural industry, bushfires, rainfall, storms and other things we care about?”

Climate change is expected to have a lot of different effects, some good, most bad. For many, we don’t know exactly how they depend on temperature, but other effects depend on temperature in a predictable, simple way. This report lists a few. They point out that

  • For each degree centigrade that global temperatures change,┬árainfall might change by up to 5-10%
  • The peak rainfall during the heaviest storms might change by up to 3-10%, per degree centigrade.
  • Each degree of temperature increase cuts crop yields by 5-15%, unless farming practices change
  • The area of the US burnt out by wildfires would increase by 200-400% per degree.

They mention other effects too, some long-term, but for this post I’ll zoom in on these. After all, these effects are already quite severe.

Just ask the residents of Queensland if they’d be happy with even a 0.5% increase in the rain dumped by the worst of their storms. It would have meant an extra 130 Gigalitres pouring over the Wivenhoe into the Brisbane River in January 2011. That’s what they’d have had if global temperatures were only 0.05 degrees higher.

Or ask the residents of Victoria how they’d feel if the Black Saturday bushfires had been 15% bigger. That’s what an extra 0.05 degrees would have meant.

Or think about what happens to agriculture – Annually, the ag sector earns $155,000,000,000 per year for Australia. A 0.05 degree change would reduce agricultural output by 0.25-0.5%, or about half a billion dollars every year. That’s $200 per Australian, which is on a par with the expected increase in energy bills under the Carbon Tax.

All right, we know a little bit about the effects of a 0.05 degree change in average global temperatures. I know 0.05 degrees sounds small, but as we can see, it has a large effect on things we care about. But how can we answer the original question, and find out how much the Carbon Tax will affect temperatures?

The same report I cited earlier also states “The best estimate is that 1000 Gigatons of human emitted Carbon emissions produces 1.75 degrees of warming” I got 2.5 from other data scattered around Wikipedia. Let’s go with 1.75.

Carbon Emissions under Australia's Carbon Tax (Source : Clean Energy Future)

Carbon Emissions under Australia's Carbon Tax (Source : Clean Energy Future)

The Australian government’s Clean Energy Future website has graphs showing how Australia’s emissions change with time, under three scenarios

  • No Carbon Tax / Emissions Trading Scheme
  • With the Carbon tax, but no international trading of Carbon Pollution permits
  • As part of a global pollution permit trading scheme

I’ve included the graph at the right. To work out how many tons of CO2 the Carbon tax will save, we want the area between the blue and red lines. That’s more or less a triangle, and I work out that the total reductions from the Carbon Tax Bill alone, with international trading, is about 20 Gigatons by 2050, with an estimate of, say, 70 Gigatons by 2100. This last estimate assumes the blue and red lines are almost flat after 2050 – most likely the blue line would have kept going up, meaning the Carbon tax is even more effective.

In fact, the effect of the Carbon tax will be greater than this – right now, politicians and activists in other countries are also considering their options in the face of climate change. For some of these, the fact that Australia is acting will be the deciding factor.

Anyway, what effect on global temperatures is the Senate now debating? Now we have all the figures we need to work this out. By 2050, the 20 saved Gigatons will save us from a .035 degree increase. That’s a dozen lives saved next Black Saturday, an extra $350 million each year for our farmers, or $72 billion in total – besides other benefits. By 2100, the Carbon tax will have kept temperatures lower by at least 0.13 degrees, making our farmers (and the economy as a whole) and $680 billion better off ($1.3 billion per year).

We’ve only looked at a tiny fraction of the direct effect of the government’s Carbon Tax bill. Agriculture worldwide will be better off, not just Australia’s ag sector. This will keep food prices lower for households. There are countries for which only a small increase in sea levels will cause massive dislocation and economic harm. The effects of even tiny rainfall changes on water prices is likely to be large.

In short, the climate change bill will have a measurable effect on global temperatures, and will make the rest of this century less uncomfortable for Australians. It will have even greater indirect benefits, as other countries have less and less excuse to delay action on climate change. This is aside from the possibly boundless benefit that might come if Australia becomes a leader in the provision of 21st century energy technology.


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