<div dir="ltr">Vision2020 Post: Ted Moffett<div><h1 style="box-sizing:inherit;line-height:1em;margin:20px 0px"><div style="font-size:small;font-weight:400">*****
Original material contained herein is Copyright 2000 through life plus
70 years, Ted Moffett. Do not copy, forward, excerpt, or reproduce
outside the <a href="http://vision2020.moscow.com/" target="_blank">Vision2020.Moscow.com</a> forum without the express written permission of the author.*****</div><div style="font-size:small;font-weight:400"><br></div><div style="font-size:small;font-weight:400">Over and over in climate science so called "skeptic' commentary on the Internet and elsewhere it is alleged that climate scientist and former Goddard Institute for Space Studies director James Hansen's temperature predictions exaggerated the future warming from anthropogenic global warming, in a manner that largely invalidates his scientific expertise. This is a false claim, when looking at the specifics of all of Hansen's actual predictions, and repeating it over and over, in the style, some might point out, of the current commander in chief, does not make it true: <br></div><div style="font-size:small;font-weight:400"><a href="https://democracyjournal.org/magazine/43/can-truth-survive-trump/">https://democracyjournal.org/magazine/43/can-truth-survive-trump/</a></div><div style="font-size:small;font-weight:400">
<i><b>"Republicans have, for years now, been preparing the ground for this foul
harvest: “We’re an empire now,” Karl Rove said in 2002, “we create our
own reality.” But even Rove could not quite believe what havoc such
empire had wrought in Trump."
</b></i></div><div style="font-size:small;font-weight:400"><br></div><div style="font-size:small;font-weight:400">As NASA scientist Gavin Schmidt points out in the following commentary, some of Hansen's predictions actually "underpredict" the increase in temperature: <br></div><div style="font-size:small;font-weight:400"><br></div><div style="font-size:small;font-weight:400"><a href="http://www.realclimate.org/index.php/archives/2020/01/update-day-2020/#comments">http://www.realclimate.org/index.php/archives/2020/01/update-day-2020/#comments</a></div><div style="font-size:small;font-weight:400">Excerpt from commentary below:</div><div style="font-weight:400"><font size="4"><br></font></div><div style="font-weight:400"><font size="4">"To summarize, the 1981 prediction from <span id="gmail-cite_ITEM-22959-0" name="citation"><a href="http://www.realclimate.org/index.php/archives/2020/01/update-day-2020/#ITEM-22959-0">Hansen et al (1981)</a></span> continues to underpredict the temperature trends due to an underestimate of the transient climate response. "<br></font></div><div style="font-weight:400"><font size="4">
</font><h3 class="gmail-storytitle" id="gmail-post-22959">Update day 2020!</h3>
<div class="gmail-meta">Filed under: <ul class="gmail-post-categories"><li><a href="http://www.realclimate.org/index.php/archives/category/climate-science/climate-modelling/" rel="category tag">Climate modelling</a></li><li><a href="http://www.realclimate.org/index.php/archives/category/climate-science/" rel="category tag">Climate Science</a></li><li><a href="http://www.realclimate.org/index.php/archives/category/climate-science/instrumental-record/" rel="category tag">Instrumental Record</a></li><li><a href="http://www.realclimate.org/index.php/archives/category/scientific-practice/" rel="category tag">Scientific practice</a></li></ul> — gavin @ 26 January 2020 </div>
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<p>Following more than a decade of tradition (<a href="http://www.realclimate.org/index.php/archives/2009/12/updates-to-model-data-comparisons">at least</a>), I’ve now updated the <a href="http://www.realclimate.org/index.php/climate-model-projections-compared-to-observations/">model-observation comparison page </a>to include observed data through to the end of 2019. </p>
<p>As we <a href="http://www.realclimate.org/index.php/archives/2020/01/one-more-data-point/">discussed</a>
a couple of weeks ago, 2019 was the second warmest year in the surface
datasets (with the exception of HadCRUT4), and 1st, 2nd or 3rd in
satellite datasets (depending on which one). Since this year was
slightly above the linear trends up to 2018, it slightly increases the
trends up to 2019. There is an increasing difference in trend among the
surface datasets because of the polar region treatment. A slightly
longer trend period additionally reduces the uncertainty in the linear
trend in the climate models. </p>
<p>To summarize, the 1981 prediction from <span id="gmail-cite_ITEM-22959-0" name="citation"><a href="http://www.realclimate.org/index.php/archives/2020/01/update-day-2020/#ITEM-22959-0">Hansen et al (1981)</a></span> continues to underpredict the temperature trends due to an underestimate of the transient climate response. The projections in <span id="gmail-cite_ITEM-22959-1" name="citation"><a href="http://www.realclimate.org/index.php/archives/2020/01/update-day-2020/#ITEM-22959-1">Hansen et al. (1988)</a></span>
bracket the actual changes, with the slight overestimate in scenario B
due to the excessive anticipated growth rate of CFCs and CH4 which did
not materialize. The CMIP3 simulations continue to be spot on
(remarkably), with the trend in the multi-model ensemble mean
effectively indistinguishable from the trends in the observations. Note
that this doesn’t mean that CMIP3 ensemble means are perfect – far from
it. For Arctic trends (incl. sea ice) they grossly underestimated the
changes, and overestimated them in the tropics. </p>
<img src="http://www.realclimate.org/images//cmp_cmip3_sat_ann-2-600x486.png" alt="" class="gmail-wp-image-22953"><center>CMIP3 for the win!</center>
<p>The CMIP5 ensemble mean global surface temperature trends slightly
overestimate the observed trend, mainly because of a short-term
overestimate of solar and volcanic forcings that was built into the
design of the simulations around 2009/2010 (see <span id="gmail-cite_ITEM-22959-2" name="citation"><a href="http://www.realclimate.org/index.php/archives/2020/01/update-day-2020/#ITEM-22959-2">Schmidt et al (2014)</a></span>.
This is also apparent in the MSU TMT trends, where the observed trends
(which themselves have a large spread) are at the edge of the modeled
histogram. </p>
<p>A number of people have remarked over time on the reduction of the
spread in the model projections in CMIP5 compared to CMIP3 (by about
20%). This is due to a wider spread in forcings used in CMIP3 – models
varied enormously on whether they included aerosol indirect effects,
ozone depletion and what kind of land surface forcing they had. In
CMIP5, most of these elements had been standardized. This reduced the
spread, but at the cost of underestimating the uncertainty in the
forcings. In CMIP6, there will be a more controlled exploration of the
forcing uncertainty (but given the <a href="http://www.realclimate.org/index.php/archives/2019/11/sensitive-but-unclassified/">greater spread</a> of the climate sensitivities, it might be a minor issue). </p>
<p>Over the years, the model-observations comparison page is regularly
in the top ten of viewed pages on RealClimate, and so obviously fills a
need. And so we’ll continue to keep it updated, and perhaps expand it
over time. Please leave suggestions for changes in the comments below.</p>
<h2>References</h2>
<ol><li><a name="ITEM-22959-0"></a>
J. Hansen, D. Johnson, A. Lacis, S. Lebedeff, P. Lee, D. Rind, and G.
Russell, "Climate Impact of Increasing Atmospheric Carbon Dioxide", <i>Science</i>, vol. 213, pp. 957-966, 1981. <a href="http://dx.doi.org/10.1126/science.213.4511.957">http://dx.doi.org/10.1126/science.213.4511.957</a>
</li><li><a name="ITEM-22959-1"></a>
J. Hansen, I. Fung, A. Lacis, D. Rind, S. Lebedeff, R. Ruedy, G.
Russell, and P. Stone, "Global climate changes as forecast by Goddard
Institute for Space Studies three-dimensional model", <i>Journal of Geophysical Research</i>, vol. 93, pp. 9341, 1988. <a href="http://dx.doi.org/10.1029/JD093iD08p09341">http://dx.doi.org/10.1029/JD093iD08p09341</a>
</li><li><a name="ITEM-22959-2"></a>
G.A. Schmidt, D.T. Shindell, and K. Tsigaridis, "Reconciling warming trends", <i>Nature Geoscience</i>, vol. 7, pp. 158-160, 2014. <a href="http://dx.doi.org/10.1038/ngeo2105">http://dx.doi.org/10.1038/ngeo2105</a>
</li></ol>
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