>Climate Modelers Reproduce Early 20th Century Warming With The Help Of Outdated Solar Forcings

>INITIAL NOTE

This is a look at the impacts of outdated TSI reconstructions used by climate modelers. The Lean et al and the Hoyt and Schatten TSI reconstructions are discussed.

INTRODUCTION

The illustration of Climate Change Attribution from the Global Warming Art website has reared its head once again. Recently, yet another AGW proponent used it to show the recent dominance of anthropogenic greenhouse gases on climate. He wrote, “Here is a graphic from an attribution study:
http://www.globalwarmingart.com/wiki/Image:Climate_Change_Attribution_png
“Do note that global warming (so-called greenhouse) gases dominate in recent years, in agreement with this latest field study.”

Figure 1 is a copy of the referenced illustration.

http://i39.tinypic.com/2s0o2uo.jpg
Figure 1

The blogger apparently didn’t bother to delve into the study that served as the basis for the graphic, nor did he investigate the forcings used in the study.

As discussed in AGW Proponents Are Two-Faced When It Comes To Solar Irradiance As A Climate Forcing, the study used by Global Warming Art is Meehl et al (2004). “Combinations of Natural and Anthropogenic Forcings in Twentieth-Century Climate”. A link to the paper:
http://www.cgd.ucar.edu/ccr/publications/meehl_additivity.pdf

And as noted in my earlier post, the solar study referenced by Meehl et al is Hoyt and Schatten (1993) “A discussion of plausible solar irradiance variations”. Yes, that’s right, 1993. Refer to Table 1 in Hoyt et al and to the discussion on page 3723 to confirm the source of solar data.

ANOTHER LOOK AT THE HOYT AND SCHATTEN TSI DATA

It is generally accepted that global temperature responds approximately 0.1 deg C as Total Solar Irradiance (TSI) varies through the solar cycle. For those who need confirmation of this, in the GISS Surface Temperature Analysis, Global Temperature Trends: 2007 Summation, they wrote, “This cyclic solar variability yields a climate forcing change of about 0.3 W/m2 between solar maxima and solar minima. (Although solar irradiance of an area perpendicular to the solar beam is about 1366 W/m2, the absorption of solar energy averaged over day and night and the Earth’s surface is about 240 W/m2.) Several analyses have extracted empirical global temperature variations of amplitude about 0.1°C associated with the 10-11 year solar cycle, a magnitude consistent with climate model simulations, but this signal is difficult to disentangle from other causes of global temperature change, including unforced chaotic fluctuations.”

http://data.giss.nasa.gov/gistemp/2007/
I’ll replay the quote again later.

In this post, TSI has been scaled so that the variations in the solar cycle reflect a global temperature variation of approximately 0.1 deg C for the past three cycles.

Figure 2 is a comparative graph of two TSI reconstructions after they’ve been scaled to reflect their impacts on Global Temperature anomaly. The blue curve marked Svalgaard is based on the current understanding of TSI variations, while the purple curve uses the Hoyt and Schatten TSI reconstruction data employed by Meehl et al. The data begins in 1880, the first year of GISS and NCDC global temperature indices. The final year, 1979, was dictated by the availability of the Hoyt and Schatten data.
http://s5.tinypic.com/e7i71l.jpg
Figure 2

Note how the Hoyt and Schatten TSI reconstruction would impose an approximate 0.19 deg C/Century erroneous linear trend on global temperature. (0.19 deg C/Century is the difference between the Hoyt and Schatten and the Svalgaard trends.)

In their “Frequently Asked Question 3.1 – How are Temperatures on Earth Changing?” of AR4, the IPCC states that global “surface temperatures have in­creased by about 0.74°C over the past hundred years.” Link to IPCC reference:
http://www.gcrio.org/ipcc/ar4/wg1/faq/ar4wg1faq-3-1.pdf

Figure 3 is the top half of FAQ 3.1 Figure 1 of the IPCC supplement.
http://s5.tinypic.com/vowo7c.jpg
Figure 3

The use of the Hoyt and Schatten data wrongly accommodates 26% of that rise (0.19 deg C/Century divided by 0.74 deg C/Century).

Basically, modelers use outdated data in failed attempts to duplicate the rise in global temperatures during the early part of the 20th Century, Figure 4.
http://s5.tinypic.com/30nf0rb.jpg
Figure 4

THE SAME HOLDS TRUE FOR MODELS THAT USE THE LEAN et al RECONSTRUCTION

In Figure 5, the linear trends of the Lean at al and Svalgaard TSI reconstructions (Scaled to Global Temperature Anomaly Impact) are compared. The data starts in 1880 again, and the Lean et al reconstruction ended in 1999, so the graph covers this period. As illustrated, the use of Lean et al by climate modelers would erroneously add approximately 0.14 deg C/Century to the model’s linear trend.
http://s5.tinypic.com/2drrspy.jpg
Figure 5

And again, it’s an attempt to replicate the rise in global temperature anomaly during the early part of the 20th Century. Refer to Figure 6.
http://s5.tinypic.com/2e5mcds.jpg
Figure 6

And what GCM uses the Lean et al TSI reconstruction to hindcast global temperature anomalies from 1880 to 2003?

The GISS Model E.

Refer to Hansen et al, 2007, “Climate simulations for 1880–2003 with GISS modelE”, “Climate Dynam.”, 29, 661-696, doi:10.1007/s00382-007-0255-8. (Note that the first pdf file is ~24MB.)http://pubs.giss.nasa.gov/docs/2007/2007_Hansen_etal_3.pdfSupplemental Information:http://pubs.giss.nasa.gov/docs/2007/2007_Hansen_etal_3_supplement.pdf

The radiative forcings used are discussed and documented by GISS here:http://data.giss.nasa.gov/modelforce/http://data.giss.nasa.gov/modelforce/RadF.txt

Figure 7 is a graph of the Solar Forcing from the above GISS Global Mean Effective Forcing link. There’s no mistaking the Lean et al curve.
http://i33.tinypic.com/2it625e.jpg
Figure 7

BUT A CURIOUS THING HAPPENS AFTER THE SOLAR FORCING DATA IS INPUT TO THE GISS MODEL E

On one hand, as noted above, GISS states, “Several analyses have extracted empirical global temperature variations of amplitude about 0.1°C associated with the 10-11 year solar cycle, a magnitude consistent with climate model simulations…”

Yet the output of the Model E with only Solar forcings does not reflect that.
http://s5.tinypic.com/s6m71z.jpg
Figure 8

And climatologists wonder why people are skeptical of climate models!

TO DOWNLOAD THE SOLAR ONLY MODEL E OUTPUT

Follow the links to the data used to create the GISS output data for Figure 8:

In the following, select “Lat-Time” in “Table 1”, “2 Miscellaneous Forcings,” “Solar irradiance.”
http://data.giss.nasa.gov/modelE/transient/climsim.html

Set the “Mean Period” in the following link to “1” (one month) and “Output” to “formatted page w/ download links”:
http://data.giss.nasa.gov/modelE/transient/Rc_jt.1.06.html

Then click on the “text file” link within the group of links marked “Download the global mean plot as PDF, Postscript, or text file” on the resulting “DATASETS AND IMAGES” page:

You’ll then have to convert the monthly data to annual means.

FURTHER COMMENTS ABOUT THE GISS MODEL E

Refer to the following two posts for additional discussions on the GISS Model E hindcasts:
http://bobtisdale.blogspot.com/2008/09/giss-model-e-climate-simulations.html
http://bobtisdale.blogspot.com/2008/09/giss-model-e-climate-simulations-part-2.html

SOURCE OF TSI RECONSTRUCTION DATA

TSI reconstruction and composite data is available from Leif Svalgaard:http://www.leif.org/research/TSI%20(Reconstructions).xls

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About Bob Tisdale

Research interest: the long-term aftereffects of El Niño and La Nina events on global sea surface temperature and ocean heat content. Author of the ebook Who Turned on the Heat? and regular contributor at WattsUpWithThat.
This entry was posted in Solar. Bookmark the permalink.

2 Responses to >Climate Modelers Reproduce Early 20th Century Warming With The Help Of Outdated Solar Forcings

  1. papertiger says:

    >It’s funny you should mention it. I just saw this graph posted by a blogger named scruffydan. skeptics aren’t deniers they are just gullibleIt’s a ways down in the comment section, if you are interested.

  2. Bob Tisdale says:

    >papertiger: Thanks. You can find my response to Scruffy Dan at the link you provided.

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