We need a 100%+ emissions cut.
What Is Progress?
The numbers show that this should be the real question at the Bali talks.
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(6). 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(7) and divided it by the current population(8). 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(11), 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The IPCC figures might also be out of date.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(12). 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”(13). 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.
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Underlying the immediate problem is a much greater one. In a lecture to the Royal Academy of Engineering in May, Professor Rod Smith of Imperial College explained that a growth rate of 3% means economic activity doubles in 23 years(24). At 10% it takes just 7 years. This we knew. But Smith takes it further. With a series of equations he shows that “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. Reading that paper I realised for the first time what we are up against.
The numbers show that this should be the real question at the Bali talks.
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(6). 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(7) and divided it by the current population(8). 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(11), 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(12). 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”(13). 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.
...
Underlying the immediate problem is a much greater one. In a lecture to the Royal Academy of Engineering in May, Professor Rod Smith of Imperial College explained that a growth rate of 3% means economic activity doubles in 23 years(24). At 10% it takes just 7 years. This we knew. But Smith takes it further. With a series of equations he shows that “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. Reading that paper I realised for the first time what we are up against.