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Published online 2 April 2008 | Nature 452, 508-509 (2008) | doi:10.1038/452508a
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Are the IPCC scenarios 'unachievable'?
Claim that the challenge of cutting emissions has been underestimated is debated.
The Intergovernmental Panel on Climate Change (IPCC) has grossly underestimated the challenges of reducing and stabilizing greenhouse-gas emissions, according to an influential group of climate-policy experts.
The scenarios produced by the IPCC assume that very substantial technological advances — leading to greater energy efficiency and reduced carbon dioxide intensity — will happen spontaneously, without extra policy measures (see page 531.
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The Pielke et al. piece is seriously flawed and misleading with conclusions that don't follow from the analysis. As but one example: Five years ago the American Enterprise Institute “proved†that the lowest IPCC emissions projection is too high, and they backed up their conclusion with actual 1990s data, whereas Pielke, Wigley, and Green have “proven†that the highest IPCC emissions projection is too low, and they backed up their conclusion with actual data from this decade. I have debunked the whole thing here: http://climateprogress.org/2008/04/02/nature-pielke-pointless-misleading-embarrassing-ipcc-technology/
If we make an assumption that today's 45gt/yr of co2-e needs to be somewhere under 20gt/yr by 2050 in order to preserve an option on 2 degrees - then how important is a more robust BAU? I would rather see work done in two areas - getting a better feel for the value of maintaining an option on 2 degrees - and developing policies that will ensure strategic, rather than just tactical, investments by those who provide and use energy. Both areas are more analytically challenging than they first appear - yet both are an integral part of responding to the bugle call referred to by Dr. Socolow.
I agree that assumptions of “spontaneous decarbonation†are not justified. Part of the problem is simply the scale of present and projected future energy demands. The scale, likely doubling demand by 2050, is beyond the reach of any known non-carbon-based technology to achieve. Another consideration is the scale of the energy requirements for carbon capture and sequestration, which will be essential to achieve stabilization at a concentration “avoiding dangerous human interference†(see analyses of Vaclav Smil). To make matters worse, James Hansen and others have a new draft paper suggesting that, accounting for slow climate feedbacks, that current models do not include, we will need to stabilize at 350 ppm (not 450) to avoid dangerous human interference: http://climateprogress.org/2008/03/17/hansen-et-al-must-read-back-to-350-ppm-or-risk-an-ice-free-planet/
The observation that spontaneity of technology development will reduce the policy or regulatory impact on climate change actions is a bit overstretched particularly when it comes from a responsible agency like IPCC ; the report seems to have overlooked or underestimated the growth trends on business as usual tenor in BASIC countries ,particularly the faster growing ones like CHINA and INDIA. The impending and most probably accelerated developments in other Afro-asian or E.European nations too seems to be not underscored. Particularly glaring is the lack of consideration for the slowening trends in technology developments in recent times especially in respect of major paradigm shifts for greener or cleaner technologies or mitigation measures and process options in a technical sense. The cost of development and the consequences of delayed development are not adequately reckoned with particularly in respect of financing mechanisms through technology alliances or faster diffusion in the developing country context ,based on developed country support mechanisms. Drastic regulatory,policy and technological as well as financial options and measures are in order to greater extent than what the IPCC projections and premises seem to suggest suresh kumar,Head,Planning and Policy ,NIIST,Trivandrum,CSIR
The IPCC scenarios are almost certainly unachievable for a simple reason – the assumptions of how much carbon is available for release into the atmosphere are probably gross overestimates. Recent revisions of available coal reserves and Hubbert linearization analyses of coal production both indicate that coal use will peak far earlier than the IPCC assumes – probably before 2030. This is not to say that the world’s total carbon reserves are too small for the IPCC scenarios, just that the amount of carbon that is feasible to access at an energy profit (and hence release into the atmosphere) is insufficient. It amazes me that the much lauded IPCC has not seriously considered the reliability of the available carbon estimates upon which they based their work. See the following articles, lectures and commentary about limitations on coal use and the IPCC scenarios: Prof. Kjell Aleklett of Uppsala University, Sweden: http://www.onlineopinion.com.au/view.asp?article=5933 ; Prof. David Rutledge of Caltech, USA: http://rutledge.caltech.edu/ ; Energy Watch Group on revision of coal reserves: http://www.energywatchgroup.org/files/Coalreport.pdf ;Commentary in New Scientist on coal by David Strahan: http://www.davidstrahan.com/blog/?p=116