2010 updates to model-data comparisons

As can be seen the long term trends in the models match those in the data, but the short-term fluctuations are both noisy and imprecise.

Looking now to the Arctic, here’s a 2010 update (courtesy of Marika Holland) showing the ongoing decrease in September sea ice extent compared to a selection of the AR4 models, again using the A1B scenario (following Stroeve et al, 2007):

In this case, the match is not very good, and possibly getting worse, but unfortunately it appears that the models are not sensitive enough.

Finally, we update the Hansen et al (1988) comparisons. As stated last year, the Scenario B in that paper is running a little high compared with the actual forcings growth (by about 10%) (and high compared to A1B), and the old GISS model had a climate sensitivity that was a little higher (4.2ºC for a doubling of CO2) than the best estimate (~3ºC).

The trends for the period 1984 to 2010 (the 1984 date chosen because that is when these projections started), scenario B has a trend of 0.27+/-0.05ºC/dec (95% uncertainties, no correction for auto-correlation). For the GISTEMP and HadCRUT3, the trends are 0.19+/-0.05 and 0.18+/-0.04ºC/dec (note that the GISTEMP met-station index has 0.23+/-0.06ºC/dec and has 2010 as a clear record high).

As before, it seems that the Hansen et al ‘B’ projection is likely running a little warm compared to the real world. Repeating the calculation from last year, assuming (again, a little recklessly) that the 27 yr trend scales linearly with the sensitivity and the forcing, we could use this mismatch to estimate a sensitivity for the real world. That would give us 4.2/(0.27*0.9) * 0.19=~ 3.3 ºC. And again, it’s interesting to note that the best estimate sensitivity deduced from this projection, is very close to what we think in any case. For reference, the trends in the AR4 models for the same period have a range 0.21+/-0.16 ºC/dec (95%).

So to conclude, global warming continues. Did you really think it wouldn’t?

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355 comments on this post.
  1. john byatt:

    Elliot, see #109 this was the response

    [Response: No it didn’t. The different scenarios have net radiative forcing in 2010 (with respect to 1984) of 1.6 W/m2, 1.2 W/m2 and 0.5 W/m2 – compared to ~1.1 W/m2 in the observed forcing since then. The test of the model is whether, given the observed changes in forcing, it produces a skillful prediction using the scenario most closely related to the observations – which is B (once you acknowledge the slight overestimate in the forcings). One could use the responses of all three scenarios relative to their specific forcings to make an estimate of what the model would have given using the exact observed forcings, but just using scenario C – which has diverged significantly from the actual forcings – is not going to be useful. This is mainly because of the time lag to the forcings – the differences between B and C temperature trends aren’t yet significant (though they will be in a few years), and in 2010 do not reflect the difference in scenario. If you are suggesting that scenario C will continue to be a better fit, I think this is highly unlikely. – gavin]

    Try reading all comments,

  2. David B. Benson:

    Relevant to determining a prior for S in 1959 is
    http://www.realclimate.org/index.php/archives/2010/01/the-carbon-dioxide-theory-of-gilbert-plass/
    where he “lucked out” with 3.6 K in his Tellus paper
    http://onlinelibrary.wiley.com/doi/10.1111/j.2153-3490.1956.tb01206.x/abstract

  3. dhogaza:

    No, what it means is that the climate sensitivity used by Hansen was higher than current best estimates…as Gavin has pointed ut many a time.

    And we’re in this weird solar minimum … which of course denialists insist proves “it’s the sun” proving “CO2 means nothing” (stupidity left for the reader to judge). (hint, if it were just the sun we’d be seeing cooling…)

  4. JCH:

    As an amateur “graph ‘eyeballer'”, I am disappointed in my fellow eyeballer’s performances here. T is obviously about to pierce scenario C and leave it in the dust. As quickly as T fell away from scenario B, it could also catch up.

    I don’t know how it will do this. Us graph eyeballers are ethically restrained from guessin’ on things, but maybe China and India will install scrubbers on their smokestacks. Somethun’ like that could happen.

  5. jacob l:

    What setting of ocean was uesd for the 1988 runs, I used mixed-layered with deep difffusion
    Year CO2-eq Temp 1958-2010
    1958 309.2 0.05
    1959 307 0
    1960 301 -0.08
    1961 291 -0.18
    1962 287 -0.14
    1963 249 -0.3
    1964 223 -0.39
    1965 255 -0.45
    1966 281 -0.33
    1967 294 -0.24
    1968 280 -0.24
    1969 274 -0.37
    1970 298 -0.28
    1971 310 -0.29
    1972 316 -0.25
    1973 311 -0.19
    1974 305 -0.24
    1975 283 -0.21
    1976 307 -0.28
    1977 323 -0.16
    1978 326 -0.14
    1979 329 -0.08
    1980 338 0
    1981 341 0.02
    1982 275 -0.12
    1983 251 -0.33
    1984 305 -0.21
    1985 330 -0.11
    1986 332 -0.08
    1987 341 0
    1988 351 -0.01
    1989 363 0.03
    1990 364 0.11
    1991 297 -0.08
    1992 221 -0.36
    1993 303 -0.25
    1994 343 0.02
    1995 361 0.05
    1996 367 0.14
    1997 372 0.13
    1998 384 0.2
    1999 392 0.36
    2000 397 0.42
    2001 397 0.37
    2002 399 0.4
    2003 401 0.45
    2004 400 0.51
    2005 399 0.48
    2006 399 0.51
    2007 400 0.55
    2008 401 0.55
    2009 405 0.52
    2010 410 0.52