Bob Tisdale has a major post up at WUWT. I broadly agree with his analysis, but think he has missed something important. The graph below shows NINO 3.4 SST anomalies scaled to compare with ‘Rest of World’ SST anomalies. The divergences where ‘Rest of World’ drops below NINO 3.4 SST are attributed by Bob to the effects of the El Chichon and Pinatubo volcano eruptions in 1983 and 1991. I think there’s more going on than that though, so I’ve added the TSI record (in red) to the graph and shaded in green the 2003-2006 series of mini El Nino’s too.
TSI in red and extra green shading added to Bob Tisdale’s graph.
As you can see, the big El Ninos in 87, 97 and 2010 all started around solar minimum, and the SST’s rose worldwide as the solar cycles grew. These were the events where the ‘rest of world’ SST’s stayed higher while the East Pacific dropped into La Nina conditions. I suggest this is largely due to reduced cloud.
Contrast this with the El Nino events in 83, 93-96 and 2003-2006. These all occur on the trailing side of the solar cycles, and afterwards, the ‘rest of world’ SST’s drop below the East Pacific SST’s. Notice though, that in 83 and 2003-2006 the ‘rest of world’ SST’s do rise, but not as much as the scaled NINO index. It’s only really the Pinatubo eruption that seems to send the ‘rest of world’ SST’s strongly downwards. It seems likely that increased cloud as the solar cycle weakened, along with the volcanic aerosol from Pinatubo muted the ‘rest of world’ SST response at the time of these solar max lagging events.
So in conclusion, I’m saying that the volcanic forcing is over-rated, because a goodly proportion of the negative forcing attributed to them in the satellite age is actually due to to solar forcing of cloud variation. This viewpoint is further backed up by the general reduction in cloud from ~1960-1998 while the Sun was strong revealed by the new Spanish and Chinese studies published in the literature this year.
Of course, the co2 theorists need a strong negative volcanic forcing to get their models to work, given the overblown positive forcing they attribute to co2. So I expect continued studied ignorance of the solar effect on cloud to continue.
I’ve been trying to get Bob to extend his interest to the reason why successive positive phases have led to upward temperature steps but he declined.
Solar induced cloudiness variations on the timescale MWP to LIA to date is the most likely in my opinion.
Then the next step is to determine whether the cloudiness changes relate primarily to changes in jetstream meridionality / zonality as proposed by me rather than the Svensmark idea about cosmic rays.
And on the decadal scale too if Prof Nir Shaviv is right about the terrestrial amplification of solar variation: http://sciencebits.com/calorimeter
I think the real impact of solar variation on surface temperature over the solar cycle is masked by a couple of things:
1) The tendency for big el ninos to occur just after solar minimum.
2) The tendency for the subsequent la ninas to occur around solar maximum. This diminishes the apparent effect of solar variation over the ~11 year cycle to around 0.15C, when in fact it produces temperature swings of up to 0.8C as witnessed in big El Nino events and the subequent La Nina’s. That big store of energy in the Pacific Warm Pool hiding from the surface record is solar derived.
And the real climatic impact of solar variation over the longer terms is masked by a few more things
1) Ignorance about the effect of solar activity changes on volcanic activity levels
2) Svalgaards tendency to iron the sunspot data flatter
3) A failure to appreciate just how little the Sun needs to vary to produce a MWP-LIA cooling or LIA-Recent warm period warming. If Nir Shaviv is somewhere near with his estimate, the sun only needs to vary by around 0.1% (which it does every average 11 year cycle anyway) over 300 years to produce a 0.5% variation in Earth’s surface temperature = ~1.5C
Here’s Bob’s typcally cautious reply:
Bob Tisdale says:
September 17, 2012 at 4:12 am
tallbloke says: “I suggest this is largely due to reduced cloud…”
Please provide data to support your suggestion. I’m not disagreeing with you, but you haven’t provided anything to confirm it. If you’re using the ISCCP cloud amount data, there are two problems with it. The early data was impacted by volcanic aerosols, and there’s also a wide band of data missing across the western Indian Ocean before the late 1990s.
Here’s my response:
Hi Bob, well I did mention the Spanish and Chinese studies which were covered here on WUWT recently. I didn’t think it was too controversial any more. Especially considering you invoke reduced cloud during La Nina to ‘recharge’ the Pacific Warm Pool for the next El Nino.
Which cloud data did you use to support that hypothesis if not ISCCP data?
tallbloke says: “It seems likely that increased cloud as the solar cycle weakened, along with the volcanic aerosol from Pinatubo muted the ‘rest of world’ SST response at the time of these solar max lagging events.”
Please supprt all of your thoughts about cloud cover with data.
Ooops, missed the fact that you had replied here with, “Which cloud data did you use to support that hypothesis if not ISCCP data?”
It’s not a hypothesis. The interaction between the tropical Pacific trade winds and cloud cover in response to ENSO have been known for decades.
To answer your question, I used the ISCCP cloud cover data but only for the tropical Pacific, which is, of course, directly impacted by ENSO. So the problem with the Indian Ocean never comes into play. Also, I started my comparisons of the impacts of ENSO in tropical Pacific cloud amount in 1995 so that they would not be impacted by the volcanic aerosols.
You know that. You’ve read my book.
Regards
Bob
PS: Thanks for the “major post” introduction. I think it’s the best post I’ve ever written
Hi Bob, As I pointed out, I also mentioned the Spanish and Chinese studies published this year and featured at WUWT. Given that:
* OLR increased from 1948,
* ocean heat content increased from 1956,
* the Sun wasn’t getting increasingly hyperactive after 1958, (but did stay highly active until 2003)
* temperature rose from ~1976,
* and the water vapour feedback needed by the models to get co2 to do anything exciting never materialised
a decrease in cloud allowing more solar heating of the ocean confirmed by at least four major studies and the satellite data looks pretty certain to me.
You may disagree.
Anyway, if it’ll make you happier, I’ll say that it was due to decreased cloud, and the rapid worldwide spreading of warm surface water brought up from the PWP by the El Nino’s, OK?
It is a great post by the way. I just wish I could get you to include the solar dimension in your analysis. Maybe once I’ve got it better quantified you’ll revisit the issue.
tallbloke: I’m not disagreeing with graph. Adding the solar cycle data as you had provides a great visual.
As you noted, I’m cautious, I like to have data to support what I write.
Thanks again for the intro and the time you’ve spent discussing this.
Regards
PS: Let’s stop chasing each other between here and WUWT. We can continue discussing this here if you prefer.
I covered a lot of this ground in a previous post that was based largely on Bob Tisdale’s work, and I’m linking to it here for whatever it might contribute to the present discussion.
http://tallbloke.wordpress.com/2012/03/16/roger-andrews-how-the-sun-caused-all-the-recent-global-warming/
Co-incidence implies causation. Solar minima produce El Ninos, solar maxima produce La Ninas. My expert consensus regards this as ‘highly likely’.