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Sunday, July 26, 2009

Real Climate's Gavin Schmidt responds to comment by John McLean, concerning the atrocious paper: McLean et al., JGR, 2009

For original Real Climate post and comments see here:

This was comment no. 56:

  1. From J. D McLean, C.R. de Freitas, R.M. Carter

    The paper by McLean et al (JGR, 2009) does not analyse trends in mean global temperature (MGT); rather, it examines the extent to which ENSO accounts for variation in MGT.

    The research concludes that MGT has for the last 50 years fallen and risen in close accord with the SOI of 5–7 months earlier and shows the potential of natural mechanisms to account for most of the temperature variation.

    It is evident in this paper that ENSO (ocean-atmosphere heat exchange) is the primary driver of MGT (i.e. El Ninos cause global warming and La Ninas cause global cooling). The reason given is Hadley circulation (which affects convection, clouds etc) linked to changes in sea surface temperature (ocean heat supply) and the Walker Circulation (i.e. ENSO). These processes might be significant factors in affecting net solar heating as well as the transfer of heat from Earth to space.

    Since so much of the criticism in the blogosphrere to date is about the failure of the McLean et al paper to detect trends, which was not the aim of the paper, these critics may be interested in a research paper that does.

    Compo and Sardeshmukh (Climate Dynamics, 32:33-342, 2009) state: “Evidence is presented that the recent worldwide land warming has occurred largely in response to a worldwide warming of the oceans rather than as a direct response to increasing greenhouse gases (GHGs) over land.”

    Further regarding trends, the warming trend from 1965 to 2000 is the same as the pre-CO2 warming trend of 1900-1940. It is clear from this the climate models promoted by the IPCC have been tuned to extra warmth associated with ENSO as is apparent in the Mclean et al paper.

    P.S. Personally I am offended, but accept it as a sign of your diligence, that in your opening sentence you fail to spell my surname correctly. Of course the incorrect spelling would have implications for your Search utility, would it not?

    [Response: We're happy to be corrected on our spelling. One presumes that you have no more serious points to make. Since no-one was in ignorance of the impact of ENSO on the global temperatures (and haven't been for decades), I'm a little puzzled as to why you think that is the relevant point of contention. Rather, you should be looking to your own press releases and the throwaway lines about trends in your paper. I take it you will be publicly contradicting your co-author's statements? (PS. the C+S paper you cite has nothing to say about attribution because they built in the trend in the SST to start with). - gavin]

    Comment by John McLean — 25 Jul 2009 @ 7:15 p.m.

And comment no. 69 by wiman:

For those here who are not aware, the authors of this paper made comments in a press release that claim that their paper accounts for most of the warming trend of the 20th century.

“ ‘The surge in global temperatures since 1977 can be attributed to a 1976 climate shift in the Pacific Ocean that made warming El Niño conditions more likely than they were over the previous 30 years and cooling La Niña conditions less likely,’ says corresponding author de Freitas.”

“‘When climate models failed to retrospectively produce the temperatures since 1950 the modellers added some estimated influences of carbon dioxide to make up the shortfall,’ says McLean.”

“Bob Carter, one of four scientists who has recently questioned the justification for the proposed Australian emissions trading scheme, says that this paper has significant consequences for public climate policy.

‘The close relationship between ENSO and global temperature, as described in the paper, leaves little room for any warming driven by human carbon dioxide emissions. The available data indicate that future global temperatures will continue to change primarily in response to ENSO cycling, volcanic activity and solar changes.’

‘Our paper confirms what many scientists already know: which is that no scientific justification exists for emissions regulation, and that, irrespective of the severity of the cuts proposed, ETS (emission trading scheme) will exert no measurable effect on future climate.’ ”

Comment by Wiman — 26 Jul 2009 @ 8:29 a.m.

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