2011-05-30 09:22:42Harries et al 2001 - problem with satellite aperture size
John Cook

john@skepticalscience...
121.222.31.47

I gave a talk at UQ on Friday night and afterwards was talking to a grizzled old skeptic. He said there was no evidence that CO2 causes warming. I cited the Harries et al 2001 satellite data. He countered with something I hadn't encountered before - said the aperture size of the 1970 satellites is different to the 2000 satellites therefore it's too difficult to compare the two datasets - the results are meaningless.

He then went on to say the sun and ocean cycles were causing global warming and when I pointed out all the evidence that showed that couldn't possibly be the case, he went onto say it stopped warming in 1998 and oceans are cooling. So not the most productive of conversations.

Nevertheless, the aperture thing was new to me. Has anyone heard this and knows if there are any valid criticisms of Harries' 2001 paper and whether his subsequent papers using other satellite series resolve the issue? If noone knows about this, I'll probably chase it up with John Harries himself but thought I'd ask on the forum before hassling the author.

2011-05-30 12:45:37
Rob Painting
Rob
paintingskeri@vodafone.co...
118.92.116.174

There was a recent paper (2011?, Lockwood?) suggesting that the solar radiative forcing was slightly overestimated due to some glitch in the measuring instruments on the old satellites. See if I can track it down. I wonder if your "skeptic" has conflated the two?

2011-05-30 12:56:19
Rob Painting
Rob
paintingskeri@vodafone.co...
118.92.116.174

It was this one A new, lower value of total solar irradiance: Evidence and climate significance - Kopp & Lean 2011

I knew it was one of those authors that has published a lot of papers on solar radiation. Note the discussion about the aperture issue. 

2011-05-30 13:51:59Papers citing Harries
John Cook

john@skepticalscience...
121.222.31.47

Using Google Scholar to see other papers that cite Harries 2001. Nothing yet (but some interesting looking papers in that list!)

2011-05-30 15:18:35
Ari Jokimäki

arijmaki@yahoo...
192.100.112.203

At least Griggs & Harries (2007) have taken differences in the aperture into consideration:

"The sampling geometry for AIRS is very different to that of the other instruments. IRIS viewed nadir through a fixed aperture and image compensation mirror. However, the detector arrangement of IMG means that two of the three detectors viewed the earth from slightly off-nadir. The detector recording the data used here is one of these off-nadir viewing detectors. To enhance spatial coverage, AIRS scans to ±49.5° cross track as the satellite moves forwards taking 90 spectra with an instantaneous field of view of 1.1° in a row perpendicular to the direction of motion. This gives a ground footprint of 13.5 km diameter at nadir but closer to 41 km by 22.4 km at 49.5°. Only the central eight spectra are used in this study to ensure that off-axis beams with significantly longer atmospheric pathlengths than that recorded by IRIS are not included. We have concentrated our study on the central Pacific region (defined as 10°N–10°S, 180°–230°E) because this region is one of the better sampled regions in all three datasets."