In addition, the authors do not account for
uncertainties in the simple model whose sensitivity is fitted.
Not exact matches
Three approaches were used to evaluate the outstanding «carbon budget» (the total amount of CO2 emissions compatible with a given global average warming) for 1.5 °C: re-assessing the evidence provided by complex Earth System
Models, new experiments with an intermediate - complexity
model, and evaluating the implications of current ranges of
uncertainty in climate system properties using a
simple model.
That would seem to be a good test of whether the method produces a good estimate of TCR independent of the
uncertainty in E. I tried such a thing, and my main objection to the Shindell (2014) paper is that when I test the «
simple» Otto method vs. the Shindell method on the same
model set
in the paper, the Otto et al (2013) method still seems to perform better.
And,
in spite of all its complexity and
uncertainties, we should not lose track of the
simple fact that theory, actual observations of the planet, and complex
models - however imperfect each is
in isolation - all point to ongoing, potentially dangerous human alteration of climate.
Because Schwartz's
model is
simpler it is easier to account for and quantify the
uncertainty in it (
in fact much of the
uncertainty in complex GCMs is hidden eg see Stainford et al referenced
in the post), so if you take the view that you are interested not just
in the mean but the variation
in the estimate Schwartz's
model, despite being
simpler, gives you better information.
If you consider the existing
uncertainties in dating and
simple linear age
model, we could get some strong leads.
But Julian, a
simple model - obs matchup
in the temperature field is not how formal attribution is done, and I agree that the aerosol forcing
uncertainty makes such
simple comparisons problematic (see Knutti's work on this for example).