[Update #4: The guys at Grist Magazine apparently have not yet read our paper, which probably explains why one of their commentators explains that everything we say is right but common wisdom, while another says that everything we say is wrong. At least they have their bases covered. Why don't these guys at Grist actually read the paper before commenting? One wonders.]

[Update #3: Andy Revkin of the NYT provides some comments as well here.]

[Update #2: John Tierney of the NYT times provides excerpts of an extended set of comments that I shared with him here.]

[Update: Here is a short interview I did with Scitizen link.]

Tom Wigley, Chris Green, and I have a Commentary in today’s Nature on the technology challenge of stabilization. It has already generated some discussion and this discussion will be the focus of some of my posts over the next weeks.

Meantime, please have a look at this summary that Tom, Chris, and I prepared:


PWG on PWG

The challenge of stabilizing the concentration of carbon dioxide (CO2) in the atmosphere may be much more difficult that currently realized. In a commentary published April 3, 2008 in Nature, Roger Pielke, Jr. (University of Colorado), Tom Wigley (National Center for Atmospheric Research) and Chris Green (McGill University) argue that the magnitude of the technology challenge associated with stabilizing the amount of carbon dioxide in the atmosphere may have been significantly underestimated by the Intergovernmental Panel on Climate Change (IPCC).

The reason for this underestimate lies in the assumptions of decarbonization common to all scenarios of future emissions growth used by the IPCC. These assumptions may be far too optimistic, and if so, will hide from view the magnitude of the technology challenge associated with stabilizing the amount of carbon dioxide in the atmosphere. In this commentary the authors reveal these assumptions, and discuss their significance for policy making.

Indeed, the authors present evidence that the first decade of the 21st century has seen greater emissions of CO2 than projected by IPCC due to rapid economic development, particularly in Asia. In recent years, the world as a whole has begun to re-carbonize, breaking a long-term trend in which carbon dioxide per unit energy was assumed instead to continue to decline indefinitely.

Stabilization of the concentrations of CO2 and other greenhouse gases is the primary objective of the United Nations Framework Convention on Climate Change (UNFCCC), approved by almost all counties, including the USA. Stabilization requires, eventually, reducing the emissions of these gases by large amounts relative to today, a task commonly referred to as “mitigation.” For CO2, mitigation requires replacing current and likely future fossil-fuel-based energy systems by carbon neutral energy sources — that is, sources of energy that are either fossil-fuel free, are accompanied by the capture and storage of CO2, or are otherwise carbon-neutral.

The costs of mitigation are generally estimated by comparing emissions under a baseline scenario where emissions evolve in the absence of climate policies, with a scenario in which the emissions are reduced (via climate policy) to achieve a chosen atmospheric concentration, called a stabilization target. Pielke, Wigley and Green note that the standard baseline scenarios considered for these calculations already include large amounts of carbon-neutral technologies that are assumed to be developed and implemented spontaneously. In the cases the authors consider, 57 to 96% of the cumulative emissions reduction required for CO2 stabilization at around 500 ppm have been assumed by IPCC to occur automatically, meaning that the majority of the emissions reduction needed to stabilize concentrations is assumed to occur automatically..

Rather than starting with assumptions about future spontaneous technological innovations, the authors’ calculations begin with a set of “frozen technology” scenarios as baselines, i.e., emissions scenarios in which energy technologies are assumed to remain at present levels. This contrasts with previous approaches, which use baselines that already include major technology changes, and, consequently, large spontaneous increases in carbon-neutral energy sources. With a “frozen technology” approach, the full scope of the carbon-neutral technology challenge is placed into clear view.

With the full scope of the technology challenge placed into view, the question then arises as to how much of this challenge will occur spontaneously, and how much must be driven by new policies. Pielke and his colleagues suggest that the amount of spontaneous development of carbon-neutral energy sources has been overestimated in previous analyses, diverting attention away from technological innovation, thereby underestimating the need for policy-driven technology development.

The authors conclude by saying “… there is no question whether technological innovation is necessary – it is. The question is, to what degree should policy focus explicitly on motivating such innovation? The IPCC plays a risky game in assuming that the spontaneous advancement of technological innovation will carry most of the burden of achieving future emissions reductions, rather than focusing on those conditions necessary and sufficient for such innovations to occur.”