PMOD vs. ACRIM Part Billion?

Question

Does anyone know of any peer reviewed papers associated with the methodology of the PMOD corrections applied to the ACRIM composite?

Quite often AGW alarmists provide arguments from websites and blogs that indicate that PMOD is the more correct choice for a TSI dataset. Alternatively there are websites and blogs as well as peer reviewed literature that indicate PMOD is invalid, and any analysis or conclusions about climate drawn from PMOD might subsequently be invalid as well. Without peer reviewed literature supporting PMOD, it is hard to take the alamists opinion on PMOD seriously, when the data does not conform to what is known.

A website that supports ACRIM.
http://scienceandpublicpolicy.org/sppi_originals/the_unruly_sunne_cannot_be_ruled_out_as_a_cause_of_recent_climate_variation.html

A Peer reviewed paper that supports ACRIM.

http://www.acrim.com/Reference%20Files/Secular%20total%20solar%20irradiance%20trend%20during%20solar%20cycles%2021%E2%80%9323.pdf

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EDIT BOB:

The difference attributes TSI accounting for as much as 60% of the warming in the 20th Century, as supported by peer reviewed literature. However I am sure you can find a blog to disputes that, but so what, you can say anything on the Internent.

EDIT BOB:

Oh my god, please stop with the two point feedback cycle you are trapped in. The authors of PMOD used the ERBS database to bridge the ACRIM gap. The authors of ACRIM used NIMBUS7/ERB to bridge the ACRIM gap. The basis that ACRIM is more accurate than PMOD is because Nimbus7/ERB takes measurements at rate of 200 times more frequent than ERBS.

EDIT Keith:

I was unable to find any of the papers that you reference yet. And your comment about the trends, you cherry picked the data, and conveniently left out the trend between minima which is .037% or about a half a watt meter^2 more energy.

EDIT Trevor:

A well though out and predicatble answer about how your favorite paper thoroughly analyzed PMOD, that's great as long as PMOD is correct. My paper uses spectral decomposition to analyze both series and finds that the sun increased it's output from 1980 to 2000 and resulted in at least 35% of the recent warming as opposed to PMOD at 10%. The trend in ACRIM accounts for about a .5 watts meter^2 between the minima. To deny that, lacks an understanding of the energy present in cyclical time series, I can understand it if you have trouble comprehending that, single analysis can be very tricky.

http://www.fel.duke.edu/~scafetta/pdf/2005GL025539.pdf

So the results are not crystal clear if you use ACRIM, if you cannot come up with a good reason to use PMOD, you are utilizing data that is in dispute.

EDIT Trevor 2:

In your professional opinion a running sum is a good way to do signal analysis on a cyclical time series? I do not believe that the laws of thermodynamics allow for mixing of future and past values of a time vs. temperature signal, I think you should reevaluate you admiration for such a crude process for signal analysis, that of course is my professional opinion, no ofense as usuall.

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Answer 1

1. Peer-reviewed literature for PMOD can be found here:

C.Frőhlich and J. Lean, 1998, "Total Solar Irradiance Variations", in: F.L.Deubner et al., Eds., "New Eyes to see inside the Sun and Stars", Proceedings IAU Symposium 185, Kyoto, August 1997, Kluwer Academic Publ., Dordrecht, The Netherlands, pp. 89-102.

C.Frőhlich and J. Lean, 1998, The Suns Total Irradiance: Cycles, Trends and Related Climate Change Uncertainties since 1978, Geophys.Res.Let., 25, pp. 4377-4380.

C.Frőhlich, 2000, Observations of Irradiance Variations, Space Science Rev., 94, pp. 15-24.

2. According to Willson's most recent computations (2007-03-03), the long term difference between PMOD and ACRIM is trivial: +0.004% per decade for ACRIM, -0.006% per decade for PMOD. That's 20 times smaller that a typical Wolf cycle variation of about 0.2 %.
http://www.acrim.com/ACRIM%20Composite%20Graphics.htm

Answer 2

The main thing for this forum is that it's a detail, not all that important in the scheme of things. The difference is small, and doesn't change the main conclusions. It's a curiosity for climatologists.

A claim has been made otherwise. That claim is based on taking two points on the curve of the ACRIM data, and drawing a straight line, ignoring the rest of the data. That's so unscientific a method, that it has no significant support in the scientific community.

My reference is admittedly a blog, but I'm only referencing the undisputed graphs showing how similar the two datasets are, and the absurdity of the use of only a few points of the data.

http://tamino.wordpress.com/2007/07/24/pmod-vs-acrim/

To answer your question. here's a peer reviewed paper re PMOD:

Fröhlich, C. and J. Lean: 2004, `Solar Radiative Output and its Variability: Evidence and Mechanisms'. Astron. and Astrophys. Rev.,12, pp. 273--320, 2004

And a detailed discussion of the issue, with several references, unreadable except by a climatologist.

http://www.ngdc.noaa.gov/stp/SOLAR/ftpsolarirradiance.html#composite

Tomcat - The only way you can come up with a 60% difference is to use the (very wrong) approach of using only 2 data points.

EDIT - OK, there are other dubious ways to mangle the data. Re Scafetta and West:

"If the two terms, I(18th C.) & I(17th C.), in the denominator have very similar values, then the problem is ill-conditioned: small variations in the input values lead to large changes in the answers; which implies very large error bounds. "

http://www.realclimate.org/index.php/archives/2006/10/how-not-to-attribute-climate-change/

There are good reasons why these arguments have gained no traction in the scientific community.

Answer 3

There's virtually no difference between ACRIM, PMOD or any of the other datasets.

Here's ACRIM...
Small version - http://profend.com/temporary/acrim-small.jpg
Large verion - http://profend.com/temporary/acrim.jpg

Here's PMOD...
Small version - http://profend.com/temporary/pmod-small.jpg
Large version - http://profend.com/temporary/pmod.jpg

Here's both superimposed on the same graph, I forgot to mention on the graph that ACRIM is red and PMOD is blue.
Small version - http://profend.com/temporary/acrimpmod-small.jpg
Large version - http://profend.com/temporary/acrimpmod.jpg

You'll note that at the point of greatest divergence the difference between the two datasets is approx 0.3 Watts per square meter per year. When compared to the mean this gives a maximum devation of 0.02% - about one fifty thousandth.

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A recent paper by Lockwood and Frohlich published in the proceedings of the Royal Society examines the evidence that the Sun is responsible for recent global warming. Those who advocate such theories have proposed several mechanisms for this to take place. One proposal is that the Sun simply got hotter, i.e., that the total energy output of the Sun ('total solar irradiance' or TSI) increased. Another proposal is that an increase in ultraviolet (UV) radiation from the Sun has caused changes in high-altitude atmospheric chemistry, leading to changes in the lower atmosphere and hence to changes in climate. Yet another proposal suggests that changes in the Sun’s magnetic field have blocked cosmic rays from striking Earth and thus preventing the seeding of clouds by cosmic rays, and warming our planet in consequence.

All these changes are associated with changes in magnetic field strength, therefore with the cosmic rays incident on the Earth. Also, satellites have directly measured total solar irradiance (TSI) for decades. Hence if some trend in TSI, or solar UV, or cosmic rays, were the root cause of modern global warming, we’ll be able to detect a trend in measurements of TSI or cosmic rays. If TSI is going up and/or solar magnetic field strength is going up and/or cosmic rays are going down, that would make the solar-cause more plausible. If not, then solar changes simply can’t be the cause of recent global warming.

Finding the trend in these variables is complicated by the fact that in addition to getting higher or lower, they oscillate up and down with the solar cycle. The Sun has a roughly 11-year cycle, during which the sunspot count goes up and down, as do TSI and magnetic field strength. Because of the change in magnetic field strength, the count of cosmic rays striking Earth fluctuates on this same cycle. Here are the measurments of sunspot counts (figure1 - R), solar magnetic field (figure 2 - Fs), cosmic ray counts (figure 3 - C), total solar irradiance (figure 4 - TSI), and Earth’s global temperature anomaly (figure 5 - ∆) for about the last 30 years.

Figures 1 to 5 (from Lockwood and Frohlich) - http://profend.com/temporary/lw1.jpg

To determine the trend, we must remove the cyclic influence, leaving only the secular change: the trend. Lockwood & Frohlich used a novel, and (in my professional opinion) very robust and reliable method, to do so. They determined these trends:

Figures 6 to 11 (from Lockwood and Frohlich) - http://profend.com/temporary/lw2.jpg

Clearly solar activity was on the increase, as indicated by increased sunspot counts, increased solar magnetic field strength, decreased cosmic ray counts, and increase TSI, UNTIL about 1985. Since then, sunspot count is down, solar magnetic field strength is down, cosmic ray counts are up, and TSI is down.

Every one of these factors would tend to cool Earth’s climate. But Earth’s temperature (according to both GISS and HadCRU) has kept going up. None of the proposed solar influences which would warm the Earth is going in the right direction to do so. In fact, over the last 30 years none of them has gone in a single direction; they’ve all gone up then down, or down then up. But Earth’s temperature has marched inexorably higher. It’s called global warming.

The result is crystal-clear: it’s not the Sun.