i think peterr was just asking questions…. so good on him

totally agree, selise — thoughtful questions are always good (and often require the most thorough responses :)

I’m trying to sort out the scientific conclusions from the political. I don’t doubt the scientists when they talk about science — but their political conclusions are a different matter.

The paper does not postulate new technologies allowing radical accelerations in the rate at which economic activity may be decoupled from CO2e production. As your comment focused upon “political conclusions” without mentioning alternative technologies in any fashion, the fact the model did not attempt to calculate how these technical factors could affect CO2e output would not appear to lie within the realm of the political conclusions you perceive in the authors’ model.

What follows is a look at what the authors actually say. I heartily recommend this technique to those offering asessments of scientific literature.

While climate change is claimed to be a central issue within many policy dialogues, rarely are absolute annual carbon mitigation rates greater than 3 per cent considered viable.

In other words, the aspect of the authors’ model dismissed as ”political conclusions” is sufficiently common as to rarely be disregarded by other climate modellers.

Peterr, can you share with us the factual basis that would allow us — and the climate modelling community — to assume that absolute annual carbon mitigation rates greater than 3 percent should be considered viable?

In addition, where mitigation polices are more developed, seldom do they include emissions from international shipping and aviation (Bows & Anderson 2007). Stern (2006, pp. 231) drew attention to historical precedents of reductions in carbon emissions, concluding that annual reductions of greater than 1 per cent have ‘been associated only with economic recession or upheaval’.

For example, the collapse of the former Soviet Union’s economy brought about annual emission reductions of over 5 per cent for a decade. By contrast, France’s 40-fold increase in nuclear capacity in just 25 years and the UK’s ‘dash for gas’ in the 1990s both corresponded, respectively, with annual CO2 and greenhouse gas emission reductions of only 1 per cent (not including increasing emissions from international shipping and aviation). Set against this historical experience, the reduction rates contained within the AB2 scenarios are without a structurally managed precedent.

In all but one of the AB2 scenarios, the challenge faced with regard to total CO2e reductions is increased substantially when considered in relation to decarbonizing the energy and process systems. Despite the optimistic deforestation and non-CO2 greenhouse gas emission scenarios developed for this paper, the repercussions for energy and process emissions are extremely severe. Stabilization at 550 ppmv CO2e, around which much of Stern’s analysis revolved, requires global energy and process emissions to peak by 2020 before beginning an annual decline of between 6 and 12 per cent; rates well in excess of those accompanying the economic collapse of the Soviet Union. Even for the 3 per cent CO2e reduction scenario (i.e. stabilization at 600–650 ppmv CO2e), the current rapid growth in energy and process CO2 emissions would need to cease by 2020 and begin reducing at between 3 and 4 per cent annually soon after.

Even if David Axelrod and his band of spin-masters merged with Rove’s minions, does anyone seriously believe they’d persuade Americans to adopt the Soviet Union’s collapse as the cost of controlling global warming?

In the cited paper, the authors describes their climate model’s use of atmospheric chemistry from current conditions and known contributions to that chemistry from human activity and consider possible paths to decreasing the human contributions under the widely shared constriants described as “political conclusions”.

Rather like this:

4. Discussion

a ) AB1 scenarios
The AB1 scenarios presented here focus on 450 ppmv CO2e and can be broadly separated into three categories.

(i) Scenarios that quantitatively exceed the IPCC’s 450 ppmv CO2e budget
range: this equates to 10 of the 18 scenarios. Scenarios in this category are quantitatively impossible.

(ii) Scenarios with current emission growth continuing until 2015, emissions peaking by 2020 and thereafter undergoing dramatic annual reductions of between 8 and 33 per cent. Scenarios in this category are, for the purpose of this paper, considered politically unacceptable.

(iii) Scenarios that, as early as 2010, break with current trends in emissions growth, with emissions subsequently peaking by 2015 and declining
rapidly thereafter (approx. 4% per year). Scenarios in this category are
discussed below.

For scenarios within category (iii) to be viable, it is necessary that the IPCC’s upper value for 450 ppmv cumulative emissions between 2000 and 2100 be correct. If, on the other hand, the IPCC’s mid- or low value turns out be more appropriate, category (iii) scenarios will either be politically unacceptable (i.e. above 8% per annum reduction) or quantitatively impossible.

However, even should the IPCC’s high level (‘optimistic’) value be correct, the accompanying 4 per cent per year reductions in CO2e emissions beginning in under a decade from today (i.e. by 2018) are unlikely to be politically acceptable without a sea change in the economic orthodoxy. The scale of this challenge is brought into sharp focus in relation to energy and process emissions. According to the analysis conducted in this paper, stabilizing at 450 ppmv requires, at least, global energy related emissions to peak by 2015, rapidly decline at 6–8 per cent per year between 2020 and 2040, and for full decarbonization sometime soon after 2050.

The characteristics of the resulting 450 ppmv scenario are summarized in
table 8. This assumes that the most optimistic of the IPCC’s range of cumulative emission values is broadly correct. While this analysis suggests stabilizing at 450 ppmv is theoretically possible, in the absence of an unprecedented step change in the global economic model and the rapid deployment of successful CO2 scrubbing technologies, 450 ppmv is no longer a viable stabilization concentration.

The implications of this for climate change policy, particularly
adaptation, are profound. The framing of climate change policy is typically
informed by the 28C threshold; however, even stabilizing at 450 ppmv CO2e
offers only a 46 per cent chance of not exceeding 2.8C (Meinshausen 2006). As a consequence, any further delay in global society beginning down a pathway towards 450 ppmv leaves 2.8C as an inappropriate and dangerously misleading mitigation and adaptation target.

(b ) AB2 scenarios

From the analysis underpinning the AB2 scenarios, it is evident that the rates of emission reduction informing much of the climate change debate, particularly in relation to energy, correlate with higher stabilization concentrations than is generally recognized. The principal reason for this divergence arises, in the first instance, from the difference between empirical and modelled emissions data for post-2000. For example, in describing ‘[T]he Scale of the Challenge’ Stern’s ‘stabilization trajectories’ assume a mean annual emissions growth almost 1.5 per cent lower than was evident from the empirical data between 2000 and 2006. While the subsequent impact on cumulative emissions for this period is, in itself, significant, the substantive difference arises from short-term extrapolations of current trends. Stern’s range of peak emissions for 2015 are some 10 GtCO2e lower than would be the case if present trends continued out to 2010, with growth subsequently reducing to give a peak in emissions by 2015.12 This substantial divergence in emissions is exacerbated significantly as the peak date goes beyond 2015. If emissions were to peak by 2020 (as was assumed for the AB2 scenarios), and again following a slowing in growth during the 5 years prior to the peaking date, emissions would, by 2020, be between 14 and 16 GtCO2e higher than Stern’s 2020 range. This difference alone equates to over a third of current global annual emissions, with knock-on implications for short- to medium-term cumulative emissions seriously constraining the viable range of long-term stabilization targets.

5 Conclusions:

Given the assumptions outlined within this paper and accepting that it considers the basket of six gases only, incorporating both carbon-cycle feedbacks and the latest empirical emissions data into the analysis raises serious questions about the current framing of climate change policy. In the absence of the widespread deployment and successful application of geoengineering technologies (sometimes referred to as macro-engineering technologies) that remove and store atmospheric CO2, several headline conclusions arise from this analysis.

—If emissions peak in 2015, stabilization at 450 ppmv CO2e requires subsequent annual reductions of 4 per cent in CO2e and 6.5 per cent in energy and process emissions.
—If emissions peak in 2020, stabilization at 550 ppmv CO2e requires subsequent annual reductions of 6 per cent in CO2e and 9 per cent in energy and process emissions.
—If emissions peak in 2020, stabilization at 650 ppmv CO2e requires subsequent annual reductions of 3 per cent in CO2e and 3.5 per cent in energy and process emissions.

[snip]

It is increasingly unlikely….[see comment 24 above]

Peterr, once you have taken the trouble to read the paper cited in the link your inital comment helped me to correct and have become conversant with the material under discussion, I’ll be delighted if you can supply to me, the study authors, and our readers examples of how what you perceive to be “political conclusions” set forth in the model are demonstrably invalid.

Invocations of Axelrod don’t cut it.

Should no such examples be forthcoming, the basis for rejecting this component of the authors’ analysis is not apparent.

http://www.ipcc.ch/pdf/assessm…..g1-spm.pdf

Linky?