When you warn people about the dangers of climate change, they call you a saint. When you explain what needs to be done to stop it, they call you a communist. Let me show you why.

There is now a broad scientific consensus that we need to prevent temperatures from rising by more than 2 degreesC 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 [1,2].

The government proposes to cut the UK's carbon emissions by 60 per cent by 2050. This target is based on a report published in 2000 [3]. That report was based on an assessment published in 1995, which drew on scientific papers published a few years earlier. The UK's policy, in other words, is based on papers some 15 years old. Our target, which is one of the toughest on earth, bears no relation to current science.

Over the past fortnight, both Gordon Brown and his adviser Sir Nicholas Stern have proposed raising the cut to 80 per cent [4,5]. Where did this figure come from? The last G8 summit adopted the aim of a global cut of 50 per cent by 2050, which means that 80 per cent would be roughly the UK's fair share. But the G8's target isn't based on current science either.

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 degrees, it suggests, by 2050 the world needs to cut its emissions to roughly 15 per cent of the volume in 2000.

The diplomats who started talks in Bali yesterday should be discussing the complete decarbonisation of the global economy.

 •  Warming up to climate change
 •  Clouds over global warming

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 per cent 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 per cent cut in the UK and a 97.7 per cent 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 per cent in the UK and 98.3 per cent 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 per cent of global warming [12]. They are likely to intensify.

A paper in Geophysical Research Letters finds that even with a 90 per cent global cut by 2050, the 2 degrees threshold "is eventually broken" [13)] To stabilise temperatures at 1.5 degrees above the pre-industrial level requires a global cut of 100 per cent. 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 [14]. 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 per cent of the necessary cut. Total decarbonisation demands that we go further. Preventing 2 degrees of warming means stripping carbon dioxide from the air. The necessary technology already exists [15]: the challenge is making it efficient and cheap. Last year Joshuah Stolaroff, who has written a PhD on the subject, sent me some provisional costings, of £256-458 per tonne of carbon [16,17]. This makes the capture of CO2 from the air roughly three times as expensive as the British government's costings for building wind turbines, twice as expensive as nuclear power, slightly cheaper than tidal power and 8 times cheaper than rooftop solar panels in the UK [18]. But I suspect his figures are too low, as they suggest this method is cheaper than catching CO2 from purpose-built power stations [19], which cannot be true [20].

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 [21]. 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" [22]. Even the age-old trend of declining energy intensity as economies mature has gone into reverse [23]. In the UK there is a stupefying gulf between the government's climate policy and the facts it is creating on the ground. How will we achieve even a 60 per cent cut if we build new coal plants, new roads and a third runway at Heathrow?

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 per cent means economic activity doubles in 23 years [24]. At 10 per cent 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 per cent 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.

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 [25]. 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.


  1. See, for example, IPCC, 2007. Climate change and its impacts in the near and long term under different scenarios. (see this link) and:

  2. Hans Joachim Schellnhuber (Editor in chief), 2006. Avoiding Dangerous Climate Change. Cambridge University Press. (see this link)

  3. Royal Commission On Environmental Pollution, June 2000. Energy & the Changing Climate. (see this link)

  4. Gordon Brown, 19th November 2007. Speech on Climate Change. (see this link)

  5. Sir Nicholas Stern, 30th November 2007. Bali: now the rich must pay. The Guardian.

  6. Intergovernmental Panel on Climate Change, 2007. Fourth Assessment Report. Climate Change 2007: Synthesis Report. Summary for Policymakers, Table SPM.6. (see this link)

  7. All the following figures are for CO2 from the burning and flaring of fossil fuel. (see this link)

  8. Currently 6,635m. (see this link)

  9. The latest figures are for 2005. (see this link)

  10. Population figures for 2005 came from here

  11. This is a conservative assumption.

  12. Josep G. Canadell et al. 25th October 2007. Contributions to accelerating atmospheric CO2 growth from economic activity, carbon intensity, and efficiency of natural sinks. Proceedings of the National Academy of Sciences. (see this link)

  13. Andrew J. Weaver et al, 6th October 2007. Long term climate implications of 2050 emission reduction targets. Geophysical Research Letters, Vol. 34, L19703. doi:10.1029/2007GL031018, 2007

  14. George Monbiot, 3rd July 2007. A Sudden Change of State. The Guardian. (see this link)

  15. Frank Zeman, 26th September 2007. Energy and Material Balance of CO2 Capture from Ambient Air. Environmental Science & Technology, Vol. 41, No. 21, pp7558-7563. 10.1021/es070874m

  16. Stolaroff's figures are $140-250/US ton-CO2. I have converted them into £/metric tonne-C. The weight of CO2 is 3.667x that of C.

  17. You can read his PhD here.

  18. Department of Trade and Industry (now the DBERR), 2003. Energy White Paper - Supplementary Annexes, p7. (see this link)

  19. The DBERR gives figures for C savings through capture-ready power stations of £460-560/tC.

  20. It cannot be true because the concentration of CO2 in thermal power station effluent is many times higher than that in ambient air.

  21. Josep G. Canadell et al, ibid.

  22. Michael R. Raupach et al, 12th June 2007. Global and regional drivers of accelerating CO2 emissions. Proceedings of the National Academy of Sciences, Vol.104, no. 24. Pp 10288-10293. (see this link)

  23. ibid.

  24. Roderick A Smith, 29th May 2007. Lecture to the Royal Academy of Engineering. Carpe Diem: The dangers of risk aversion. Reprinted in Civil Engineering Surveyor, October 2007.

  25. Jack Doyle, 2000. Taken for a Ride: Detroit's big three and the politics of pollution, pp1-2. Four Walls, Eight Windows, New York.