Comments on: Comment on McLean et al Submitted

By: Niche Modeling » No Weakening of the Walker

Niche Modeling » No Weakening of the Walker — Thu, 27 Aug 2009 04:53:19 +0000

[...] manuscript. (I know who Dr Jones is, but will preserve his anonymity) Here are a selection of gems: Dr Jones: You mix changes in variability and changes means. The slowing down of the Walker circulation is an [...]

By: Andrew

Andrew — Sat, 15 Aug 2009 23:27:42 +0000

From the paper:”However, our estimated sensitivityof global mean temperature to anthropogenic forcingwhen cSOI is included is 0:19 0:02%K=W=m2″This just happens to be very similar to the value found by Douglass and Knox 2005:http://www.pas.rochester.edu/~douglass/papers/2…and also that found by Lindzen and Choi 2009:http://www.leif.org/EOS/2009GL039628-pip.pdf

By: Andrew

Andrew — Sat, 15 Aug 2009 18:27:42 +0000

By: Andrew

Andrew — Sat, 15 Aug 2009 18:27:00 +0000

From the paper:

“However, our estimated sensitivity
of global mean temperature to anthropogenic forcing
when cSOI is included is 0:19 0:02%K=W=m2″

This just happens to be very similar to the value found by Douglass and Knox 2005:

http://www.pas.rochester.edu/~douglass/papers/2004GL022119_Pinatubo.pdf

and also that found by Lindzen and Choi 2009:

http://www.leif.org/EOS/2009GL039628-pip.pdf

By: davids99us

davids99us — Sat, 15 Aug 2009 02:38:33 +0000

Nick that is absolutely true. Correlation is necessary but not sufficient for causation. But there is only so much I am going to do for a comment, particularly it is to try to clear up the SOI correlation issue, and not the mechanisms. There does not seem to be any objection to El Nino heating, its just assumed that La Nino cools to the same degree, which some have contested. Its all in the papers cited. The simple minded mechanism is that El Nino gets locked on the heat cycle through local feedback loops, and some of that heat gets transferred globally via meridional flow and Hadley circulation, etc, and cant get away so easily (the asymmetry issue). I don't know and I don't know if anyone else knows for sure either.

By: Anonymous

Anonymous — Sat, 15 Aug 2009 02:38:00 +0000

Nick that is absolutely true. Correlation is necessary but not sufficient for causation. But there is only so much I am going to do for a comment, particularly it is to try to clear up the SOI correlation issue, and not the mechanisms. There does not seem to be any objection to El Nino heating, its just assumed that La Nino cools to the same degree, which some have contested. Its all in the papers cited. The simple minded mechanism is that El Nino gets locked on the heat cycle through local feedback loops, and some of that heat gets transferred globally via meridional flow and Hadley circulation, etc, and cant get away so easily (the asymmetry issue). I don’t know and I don’t know if anyone else knows for sure either.

By: Nick Stokes

Nick Stokes — Sat, 15 Aug 2009 02:28:52 +0000

David,firstly I think you should be commended for computing the AF data for comparison. One big fault with papers like McLean et al is that they just quote an R2 figure and say “isn't that big!”. It is important to have something to relate it to.But the weakness of your cSOI argument is summed up by the cliche “correlation is not causation”. The fact is that correlation is valuable in affirming a causative link, provided you have made that link independently. There is a well-developed theory that says that AGW (AF) could cause warming, so the correlation is significant. You haven't provided any such mechanism for cSOI. It's true that one can say that El Nino's cause temproary warming etc…, but that's an argument for SOI correlation, which fails. If you want to advance cSOI, then you would have to explain why that is plausibly causative, while SOI isn't.

By: Nick Stokes

Nick Stokes — Sat, 15 Aug 2009 02:28:00 +0000

David,
firstly I think you should be commended for computing the AF data for comparison. One big fault with papers like McLean et al is that they just quote an R2 figure and say “isn’t that big!”. It is important to have something to relate it to.
But the weakness of your cSOI argument is summed up by the cliche “correlation is not causation”. The fact is that correlation is valuable in affirming a causative link, provided you have made that link independently. There is a well-developed theory that says that AGW (AF) could cause warming, so the correlation is significant. You haven’t provided any such mechanism for cSOI. It’s true that one can say that El Nino’s cause temproary warming etc…, but that’s an argument for SOI correlation, which fails. If you want to advance cSOI, then you would have to explain why that is plausibly causative, while SOI isn’t.

By: davids99us

davids99us — Fri, 14 Aug 2009 20:56:36 +0000

Nick, You are right the a correlation with anthropogenic forcing is uninteresting. The point is that cSOI explains almost as much. This is against a background of Foster stating that SOI can only explain 7% and is insignificant to trend. cSOI demonstrates this in not true, and supplies the parameters under which it is not true, a small 5% accumulation of the heating effect of ENSO.The literature on SOI is extensive. It is the best proxy for trade wind strength, temperature difference, etc. It has more physical relevance to temperature than a tree ring width, for example.The purpose of the multi-variable model is to show the relative contribution. Given the coefficient for AF is in the right ballpark, you are getting about half the variance being explained by cSOI, and half by AF, a large part as McLean claim. In a nutshell, the increase in temperature since 1960 is restricted to a period between 1976 and 1998 where we had a series of strong El Nino and very weak La Ninas. Its the El Ninos that are responsible for a large part of the warming we observe since then. There are physical theories for it, the AR4 acknowledges it, but no-one has really quantified it properly.

By: Anonymous

Anonymous — Fri, 14 Aug 2009 20:56:00 +0000

Nick, You are right the a correlation with anthropogenic forcing is uninteresting. The point is that cSOI explains almost as much. This is against a background of Foster thinking that SOI can only explain 7% and is insignificant to trend. cSOI demonstrates this is not true, and supplies the parameters under which it is not true, a small 5% accumulation of the heating effect of ENSO.

The literature on SOI is extensive. It is the best proxy for trade wind strength, temperature difference, etc. It has more physical relevance to temperature than a tree ring width, for example.

The purpose of the multi-variable model is to show the relative contribution. Given the coefficient for AF is in the right ballpark, you are getting about half the variance being explained by cSOI, and half by AF, a large part as McLean claim.

In a nutshell, the increase in temperature since 1960 is restricted to a period between 1976 and 1998 where we had a series of strong El Nino and very weak La Ninas. Its the El Ninos that are responsible for a large part of the warming we observe since then.

All the index does is accumulate over that period, its flat elsewhere. There are physical theories for it, the AR4 acknowledges it, but no-one has really quantified it properly.