Why do skeptics love the PDO so much?

Question

It seems to me a true scientific 'skeptic' should be 'skeptical' of many of the techniques Spencer uses to support his claim that PDO is the primary driver of 20th century warming. For instance...

1. PDO records are obtained from tree ring data, a technique whose validity skeptics often criticize, and indeed contain much variation: http://www.ncdc.noaa.gov/paleo/pubs/biondi2001/fig2-lg.gif

2. He supports his theories with (admittedly highly simplified) models that he alone designed, ran and analyzed:
http://www.drroyspencer.com/research-articles/global-warming-as-a-natural-response/

3. He clearly shows how said models achieved much more respectable accuracy when coupled with CO2 forcing (using data from none other than Hansen, mind you)
(see same link as above).

4. And I should also mention the fact that his refutation for the critical and obvious question of whether or not temperature could be driving PDO, rather than his claim that it is the other way around, is little more than a simple 'no', even though it is clear from his own graphs that this may very well be the case...

Anyway. Does any of this make it strange that so many scientific "skeptics" would be so quick to assign this theory more validity than AGW?

Answer 1

Another problem with Spencer's theory is that he relies heavily on his own previous papers. That's never a good sign. You should be able to cite other scientists' work if there's a strong scientific basis to what you're doing.



One serious issue I have with his model is that he somehow allows for the positive PDO phases to have much more impact on global temperatures than the negative phases. Just compare his Figure 4 to the PDO index monthly values:

http://jisao.washington.edu/pdo/



How on Earth is he getting 0.6 deg C warming from 1900-1945, 0.3 deg C warming from 1975-Present, and just 0.2 deg C cooling from 1945-1975? That really seems like a stretch to me based on the PDO index values.



The other problem being that there was only a 0.45 deg C warming from 1910-1945 (even less if you go back to 1900), 0.1 deg C cooling from 1945-1975, and a 0.55 deg C warming from 1975-Present.

http://data.giss.nasa.gov/gistemp/graphs/Fig.A2.lrg.gif



This tells me that he's attributing too strong of a forcing to the PDO (actually cloudcover, indirectly impacted by PDO), because the amplitude of his modeled temperature changes are too large until the present, when he has to include the CO2 forcing to account for the recent warming.



I think if you look at Spencer's theory here with a truly skeptical eye, it's just not good. His model doesn't fit the data well and he's completely ignoring all but 2 forcings. Where is the solar forcing that deniers love so much? The problem is that Spencer is trying to attribute a greater forcing to PDO than it's actually responsible for, and to do so he has to neglect other forcings (like the 1 W/m^2 solar forcing from 1910-1940). Just like Scafetta&West ignore all other forcings in order to attribute a greater effect to the Sun than it's actually responsible for.



And they get similar results. Even with their unrealistic models, Spencer can only attribute about one-third of the recent warming to PDO, and Scafetta&West can only attribute about one-third to solar effects. And their models directly contradict eachother by ignoring the other's forcing.



Spencer's PDO+CO2 model isn't great, but it isn't bad. But if he made a PDO+CO2+solar model, it would be utter garbage.



Yet another issue I just noticed is that Spencer's PDO-only model has a greater warming than his PDO+CO2 model in the eartly 20th century. What the hell is that?? Increasing CO2 causing cooling?? That makes no physical sense whatsoever.



Deniers dismiss any work done with climate models as totally speculative and worthless - unless it's done by a 'skeptic' like Roy Spencer or Scafetta&West. It doesn't matter that it's an (admittedly) grossly oversimplified model. As long as it supports the denial point of view, it's gold.



But to answer your question, the reason 'skeptics' love the PDO is the same reason they love the Sun and GCRs. It's not anthropogenic!

Answer 2

If warming drives the PDO then this warming period looks a lot like the MWP, which the AGW believers refuse to acknowledge because even though it wouldn't preclude AGW today, it precludes being able to simply infer AGW from GW.

Answer 3

The people you refer to are deniers, not skeptics. A skeptic would not reject any true science out-of-hand, just as they would not accept it without further information and validation.

Someone who says they are a skeptic would not, in the same breath, declare AGW a hoax, just as they would not declare AGW absolutely true.

Answer 4

Could be because it's a good indicator and an actually plausible cause, unlike CO2 concentrations.

Answer 5

Oh dawei just give up on this section! trust me i know how you feel! the religious and spirituality section is full of stuborn atheists who are trolls and spammers! SO just leave it be!

Answer 6

it introduces uncertainty, giving them an opportunity to claim 'we dont know what we are talking about'?