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December 04, 2007

Do The Math Environment

I hate to say it, but the likelihood that the UN conference in Bali will produce reductions in carbon emissions sufficient to prevent catastrophic global warming is essentially zero. Not going to happen. Because what's really needed is not even being hinted at.

George Monbiot does the math:

There is now a broad scientific consensus that we need to prevent temperatures from rising by more than 2°C above their pre-industrial level. Beyond that point, the Greenland ice sheet could go into irreversible meltdown, some ecosystems collapse, billions suffer from water stress, droughts could start to threaten global food supplies. [...]

In the new summary published by the Intergovernmental Panel on Climate Change (IPCC), you will find a table which links different cuts to likely temperatures. To prevent global warming from eventually exceeding 2°, it suggests, by 2050 the world needs to cut its emissions to roughly 15% of the volume in 2000.

I looked up the global figures for carbon dioxide production in 2000 and divided it by the current population. This gives a baseline figure of 3.58 tonnes of CO2 per person. An 85% cut means that (if the population remains constant) the global output per head should be reduced to 0.537t by 2050. The UK currently produces 9.6 tonnes per head and the US 23.6t(9,10). Reducing these figures to 0.537t means a 94.4% cut in the UK and a 97.7% cut in the US. But the world population will rise in the same period. If we assume a population of 9bn in 2050, the cuts rise to 95.9% in the UK and 98.3% in the US.

The IPCC figures might also be out of date. In a footnote beneath the table, the panel admits that "emission reductions...might be underestimated due to missing carbon cycle feedbacks." What this means is that the impact of the biosphere's response to global warming has not been fully considered. As seawater warms, for example, it releases carbon dioxide. As soil bacteria heat up, they respire more, generating more CO2. As temperatures rise, tropical forests die back, releasing the carbon they contain. These are examples of positive feedbacks. A recent paper (all the references are on my website) estimates that feedbacks account for about 18% of global warming. They are likely to intensify.

A paper in Geophysical Research Letters finds that even with a 90% global cut by 2050, the 2° threshold "is eventually broken." To stabilise temperatures at 1.5° above the pre-industrial level requires a global cut of 100%. The diplomats who started talks in Bali yesterday should be discussing the complete decarbonisation of the global economy.

It is not impossible. In a previous article I showed how by switching the whole economy over to the use of electricity and by deploying the latest thinking on regional supergrids, grid balancing and energy storage, you could run almost the entire energy system on renewable power. The major exception is flying (don't expect to see battery-powered jetliners) which suggests that we should be closing rather than opening runways.

This could account for around 90% of the necessary cut. Total decarbonisation demands that we go further. Preventing 2° of warming means stripping carbon dioxide from the air. The necessary technology already exists: the challenge is making it efficient and cheap. [...]

The Kyoto Protocol, whose replacement the Bali meeting will discuss, has failed. Since it was signed, there has been an acceleration in global emissions: the rate of CO2 production exceeds the IPCC's worst case and is now growing faster than at any time since the beginning of the industrial revolution. It's not just the Chinese. A paper in the Proceedings of the National Academy of Sciences finds that "no region is decarbonizing its energy supply." Even the age-old trend of declining energy intensity as economies mature has gone into reverse. [...]

Underlying the immediate problem is a much greater one...[A] growth rate of 3% means economic activity doubles in 23 years. At 10% it takes just 7 years...Each successive doubling period consumes as much resource as all the previous doubling periods combined. In other words, if our economy grows at 3% between now and 2030, we will consume in that period economic resources equivalent to all those we have consumed since humans first stood on two legs. Then, between 2030 and 2053, we must double our total consumption again. [...]

But I am not advocating despair. We must confront a challenge which is as great and as pressing as the rise of the Axis powers. Had we thrown up our hands then, as many people are tempted to do today, you would be reading this paper in German. Though the war often seemed impossible to win, when the political will was mobilised strange and implausible things began to happen. The US economy was spun round on a dime in 1942 as civilian manufacturing was switched to military production. The state took on greater powers than it had exercised before. Impossible policies suddenly became achievable.

The real issues in Bali are not technical or economic. The crisis we face demands a profound philosophical discussion, a reappraisal of who we are and what progress means. Debating these matters makes us neither saints nor communists; it shows only that we have understood the science.

I'd like to think that humans can look at the science, do the math, draw the conclusions, and do what's necessary. But it's not going to happen. Certainly not any time soon. Only when they feel like their very survival is threatened will people make the needed changes and sacrifices. Realize that we're not talking about cutting emissions by a few percent here, a few percent there. We're talking about cutting carbon emissions almost to zero. Monbiot says it's not impossible and invokes the example of WWII, but people are a long way from feeling anything like the level of urgency they felt during WWII. The problem is that the threat is relatively abstract (not a sabre-toothed tiger or an invading army, but a prediction made by scientific modeling) and it's happening in slow motion (not in geological terms, certainly, but in terms of the average human life span). When people make life-changing decisions, there's a huge emotional component. Hardly anybody feels anything like the emotional urgency that would be required for the "complete decarbonization of the global economy." It's nowhere on anybody's to-do list.

A note on the math. I've written a number of times in the past (for example, here) about the crucial importance of understanding exponential growth. Think compound interest: growth by a steady percentage per year. Which is equivalent to growth by doubling at a constant rate. And, as Monbiot notes, when you grow by doubling, each step is greater than the sum of all the preceding steps. Consider the sequence 1, 2, 4, 8, 16, 32, and so on. Each number in the sequence is greater (by one) than the sum of all the preceding numbers. Check it for yourself. So if something grows at a rate of 3% a year, say, that sounds pretty innocuous. But that means it doubles about every 24 years, and during that 24 years it increases more than it has in all previous history combined. We're good at creating exponential growth, but we're not wired to grasp its implications, and that may be our species' fatal flaw.

Posted by Jonathan at December 4, 2007 11:14 PM  del.icio.us digg NewsVine Reddit YahooMyWeb


Some comments on this subject from the UK:



Posted by: Dave Moorman at December 5, 2007 01:57 PM