Contradictions in the Garnaut Report (ii)


The Garnaut Report sets out targets for reductions of greenhouse gas emissions allegedly responsible for dangerous climate change. Its preferred target is “holding” emissions to just 10 percent of the 2000 level by 2050. This paper shows the Report’s targets are overstated because its model underestimates the extent of biospheric uptakes of the main greenhouse gas, carbon dioxide, CO2, and fails to show that the greater are emissions, the larger are those uptakes. The targets are also based on false claims the biosphere is already “saturated” with CO2. In reality the “Airborne Fraction” of anthropogenic emissions has averaged only 43 percent of total emissions since 1958. Other errors include its treatment of the international agreements needed to secure large reductions in emissions as the free-rider problem of the “Prisoners’ Dilemma” and its use of marginal utility theory to justify the low discount rates needed to sanction costly strong action now, which overlooks the St. Petersburg Paradox. The Emissions Trading Scheme (ETS) proposed by the Report is likely to undermine the Australian economy by rendering much of its primary and industrial production unprofitable.


1.      Stern (2007:218) like the Report accepts that emissions of CO2-e need only be reduced to the level of “natural absorption”, but is both more precise and more wrong: “in the long term global emissions will need to be reduced to less than 5GtCO2e, over 80 percent below current annual emissions [c.25GtCO2e]”. In fact uptakes of CO2 alone were already over 18.35GtCO2 in 2005 (Canadell et al. 2007: Table 1). Stern relied on the modelling by Meinshausen et al.2006 which excludes any role for Uptakes. 

2.      This author provided both the equations of the carbon budget and the data in Table 1 to the Garnaut Climate Change Review, Curtin 2008a, but see Le Quéré 2008. The sinks that absorb [CO2] are hardly ever specified in the various modelling exercises of the IPCC (Randall and Wood et al.) that make use (2007:644) of the MAGICC model (Wigley et al. 2002, Wigley 2008). This does not directly enter negative elements in the carbon budget, i.e. the uptakes. Instead they are projected at whatever is the level needed to validate the emission and concentration scenarios of its component models (Wigley 1993: Table 2). Randall and Wood (2007) cite the claim in Friedlingstein et al. (2006) “that in all models examined, the sink decreases in the future as the climate warms”. The claim by Canadell et al. (2007) that the rate of growth of biospheric absorption of CO2 emissions is slowing relative to the growth of emissions depends heavily on choice of terminal dates. The claim appears valid if the final year is an El Nino year, but not otherwise.   Such claims also ignore the observations in Long et al. 2006 and Norby and Luo 2004. See also Curtin 2007.

3.      For example, The Australian, 1st October 2008: “Eat Kangaroo to help combat climate change”: “[Garnaut cites researchers who] conclude that by 2020, beef cattle and sheep numbers in the rangelands could be reduced by seven million and 36 million respectively, and that this would create the opportunity for an increase in kangaroo numbers from 34 million today to 240million by 2020”. The Report did not mention the impact of these reductions on Australia’s exports of beef (which account for two-thirds of total production), wool, and sheep.

4.       The Report advises against cash payments that would enable the non-rich to maintain their present real spending on petrol and electricity, in favour of payments in kind. However the Green Paper of 16th July 2008 proposes that compensation will be payable in cash, which it claims “should not blunt the incentive to change behaviours in ways that result in lower emissions” (Summary: 25).

5.       The Report endorses Jevons who in The Coal Question (1865) predicted exhaustion of the UK’s coal reserves by the 1920s; so far from being exhausted as many as 14 new coal mines are about to be developed to supply the country’s planned six new coal-fired power stations. The Report also praises the Club of Rome for its projected total depletion of all nonrenewable fuels and other minerals by 2100 (1974: Fig.35), and even brings forward some of the depletion dates, e.g. for gas, oil, nickel, copper, and zinc, to 2050 (2008: Table 3.3). It is far from clear why, if oil and gas reserves will be exhausted at the 2007 production rate by 2060 at the latest, the Report considers it necessary to include these fuels in its ETS. Turner (2008) correctly points out that the Club of Rome unlike the Ehrlichs (1970) did not forecast complete collapse of the world economy by 2000 as many have claimed it did, instead their terminal date “for collapse of the global system” due to depletion of non-renewable resources and rising [CO2} was 2050 (Turner 2008). This is explicitly endorsed by the Garnaut Review with its encomium (p.69) on the Club of Rome, which would seem to suggest we should eat drink and be merry rather than attempt to stave off the inevitable with the damaging ETS.


I am indebted to Ian Castles, Ray Evans, Michael Hammer, James Haughton, Andrew Hodges, Stephen Howes, Ken Macoun, Peter Morgan, John Millett, David Pilbrough, Geoff Smart, Tom Quirk and two anonymous reviewers for their insights and suggestions. All errors are mine.


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  1. The right vertical axis measures the Airborne Fraction (AF %) as the percentage of CO2 emissions that remains in the atmosphere. Note that high AF years coincide with El Niño years and the low uptakes in those years (due to droughts).
  2. The cited source shows that in 1959 3.87 GtC (billion tonnes of Carbon) were emitted by hydrocarbon fuel consumption and other sources of CO2 emissions including land use change (LUC), and reached 9.94 GtC in 2007. The evident spurt in the growth trend after 2000 reflects rapid growth of hydrocarbon fuel usage in China and India amongst others.
  3. The Total Uptakes curve shows the absorption of emissions by natural processes. Despite wide variability, invariably associated with the El Niño-La Niña (ENSO) phenomenon, the net effect is that the Uptakes track the Emissions remarkably closely on average, such that the log linear trend of the Airborne Fraction is basically flat after 1980.
  4. That is because while evidently El Niño years result in the lower biospheric Uptakes depicted by the bottom curve (mostly via photosynthesis but including direct absorption by the oceans), La Niña years produce higher Uptakes, and hence produce a lower Airborne Fraction in those years. The annual average absorption of Emissions by Uptakes from 1959 to 2007, as shown by the source’s mid-year data used here, is 56.5 percent of the Emissions.

Source: www.gmacweb.env.uea.ac.uk (accessed 23 October 2008, updated for July 2007 to July 2008 from NOAA).


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