Arnold Kling  

The Sun and Global Warming

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N. Scafetta and B.J. West write,


We find good correspondence between global temperature and solar induced temperature curves during the pre-industrial period such as the cooling periods occurring during the Maunder Minimum (1645–1715) and the Dalton Minimum (1795–1825). The sun might have contributed approximately 50% of the observed global warming since 1900

They do not use a climate model. It is hard for me to tell, but I think that what they are doing is what econometricians would call "reduced-form" estimation rather than structural estimation.


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COMMENTS (14 to date)
Felix writes:

Global warming is the ultimate lagging indicator. And in fact the world has only got a little bit warmer since 1900, so you can use anything you like to explain that. But the fact is that CO2 levels will certainly cause much higher temperatures going forwards, and that CO2 levels are rising to, um, stratospheric levels -- well over double where they've ever been in the past. And the connection between CO2 levels and future warming is certain: even the Bush Administration admits it. So this is really silly.

Robert Speirs writes:

Interesting, commenter. So no actual man-made global warming has happened yet? Funny, that's not what the eminent climate scientist Al Bore has been saying. And I would say the chances of increased CO2 causing global warming are about the same as the chances of the weather forecast's number for the day after tomorrow's temperature being right on the money. After all the same sorts of computer models are being used for both extremely dubious predictions. And why should the leftists, whose only real interest is in destroying the most successful economy in the history of the world, cite what the Bush administration is saying now, when they refuse to listen to anything else they say? But then, the only thing I know about the weather is that I don't know anything about the weather. Of course, that means I know more about it than most people or scientists.

Felix writes:

Oh, global warming has happened -- just look at the north pole, or any glacier field you care to mention, over the past 30 years or so. We can see that a relatively small amount of global warming has had enormous effects in polar areas, and we can easily extrapolate what's going to happen as the warming continues and indeed accelerates.

As for the chances of CO2 causing global warming, they're 100%. Don't take my word for it, read the IPCC report.

I have one request for the global warming advocates.

Show me where climatology has made even one significant and accurate prediction of future conditions without the *opposite* prediction enjoying similar support.

Without significant evidence of its predictive ability, climatology is no better than astrology.

John Fleck writes:

If you read the entire Scafetta and West paper, you'll see that they also note that the temperature-sun connection breaks down over a good part of the 20th century, and that solar variability is insufficient to explain the exhibited warming, especially over the last 30 years or so. See their figure 2: "Note the good correspondence of the patterns in particular during the pre-industrial era (1600–1900) and the significant discrepancy occurring in the 20th century with a clear surplus warming." That surplus warming is what is commonly called anthropogenic.

Robert Speirs writes:

As to the CO2 link being "100% true", I am 100% convinced that nothing in climate science is that true. And if you do read the paper you see that the secondary effects of the sun's warming have not been assessed so as to say that any warming other than that produced by primary and direct increases in insolation is necessarily anthropogenic. So even these authors do not definitively state that global warming could not be caused only by the direct and indirect effects of the increase in the sun's activity.

John writes:

"And the connection between CO2 levels and future warming is certain: even the Bush Administration admits it."

And the Bush administration said Iraq had WMDs? I don't trust a word of what they say.

"As for the chances of CO2 causing global warming, they're 100%. Don't take my word for it, read the IPCC report."

Have you read the IPCC report or just the policy maker's summary? The summary is significantly more bullish on warming than the report itself.

"That surplus warming is what is commonly called anthropogenic."

It's unexplainable by the model. Models are imperfect especially in climate science. By this model surplus warming could be explainable by a host of factors, not limited to anthropogenic ones.

Mr. Econotarian writes:

It should be kept in mind that the Earth has gone through as period of 2 degrees C higher temperature than today during the Pliocene:

http://geology.er.usgs.gov/eespteam/prism/prism3main.html

The planet made it through. If we want to save people in particular though, they better get wealthier.

Dezakin writes:

Everyone allways asks the wrong questions with climate change, and it gets so annoying... especially on an economics blog.

1) Is climate change happening? Probably; The data seems fairly conclusive that it is, and continues an average warming trend. Many ideologues dont even get this far.

2) Is the climate change anthropogenic? Probably. There is a significant effect predicted in most models from CO2 concentrations. The concensus is that its anthropogenic, but many ideologically inclined refused to consider it. Whats interesting about this question is its totally unimportant.

3) Is there anything we can do about climate change? This is a much more important question than whether its 'our fault.' It doesnt matter if climate change is anthropogenic or not, it only matters if humans can mitigate climate change, whether by reducing emitions or increasing particulate aeresols (the environmental lobby sure wouldnt like that I imagine) to influence the atmospheric reflection. The concensus on this is far from sure; How much can we actually reduce of CO2 concentration, how much difference does it make? No one really knows this.

4) Are the costs of the mitigations less than the costs of dealing with climate change? Given how little we know about what we can do to curb climate change, how could we possibly manage to make a rational policy decision on a cost/benifit basis. We can't.

We can do things that are essentially free. Mandating all future municipal power plants cant be coal fired for instance, because nuclear works at nearly the same cost, and leaves the coal free for synthetic fuel production anyways.

Geoffrey writes:

Just a comment on an incredibly common misconception.

Felix above writes...

"CO2 levels are rising to, um, stratospheric levels -- well over double where they've ever been in the past"

Which unfortunately is terribly wrong..
Both temperature and CO2 are at historic lows

See nice graph here..
http://www.geocraft.com/WVFossils/Carboniferous_climate.html

CO2 levels during the Jurrassic period were about 5 times higher than they are today. Average global temperatures were about 10 degrees C higher.

CO2 levels during the Cambrian period were 19 times hgier than todays levels.

We have a long way to go before the "Oh my God we are all going to die" stage.

Dezakin writes:

"Which unfortunately is terribly wrong..
Both temperature and CO2 are at historic lows"

There have been times in geologic history where CO2 and temperature have been lower and higher, but in the history of human civilization its fairly accurate to say CO2 is far higher.

"We have a long way to go before the "Oh my God we are all going to die" stage. "

Strawman arguments like this are unnecissary. I don't know any that are insinuating that climate change is fatal to the planet or to humanity. The concern is that it's upsetting to human civilization and disruptive economically.

My assertion is that we cant make any policy decisions because we dont know what mitigations will be worthwhile and whether they'll be worth the cost, so its far less important to worry about than something that we can calculate the odds on, like a massive meteor strike.

RogerM writes:

Nothing like GW to get the juices flowing! As a dumb economist, I have yet to see data or analyses to convince me that CO2 causes global warming. Everything I have seen shows that CO2 increases at the same time as temperatures, but that doesn't guarantee a cause/effect relationship. Scientists refuse to consider that both maybe caused by a third variable.

jb writes:

The facts as I understand them:
* The temperature of the earth is rising. It is not, however, as hot as it has been at previous points in human history. (I can't find the cite right now, but I do know that hippopatumus lived in the Thames river 4000 years ago)
* However the level of carbon dioxide in the atmosphere is significantly higher than it has ever been in the last 800,000 years
* The additional carbon dioxide will cause the earth to warm slightly.
* But each additional "chunk" of carbon has a reduced warming effect - if X tons of carbon increase temperature by Y, 2X tons only increase temperature by Y+ (Y/ some positive number > 1)
* But the real danger isn't the carbon dioxide, it's the water vapor - the additional heat from carbon will cause more water to evaporate, increasing the water vapor in the air. Water vapor is the most powerful/ubiquitous greenhouse gas
* As more water vapor is added to the atmosphere, generally scientists believe that it will increase cloud cover

And that's where the certainty ends. The follow up question is "What happens when there are more clouds" and the answer is "inconclusive" - the reduction in sunlight might induce a cooling effect, the increase in cloud insulation might induce a warming effect, or there might be a little of both.

My non-expert opinion on this is that additional cloud cover will probably reduce daytime temperatures and increase nighttime temperatures. My guess, given the previous prehistoric warming cycles, is that the net effect will be a cooling one, significantly dampening the impact of all of the additional carbon. Otherwise, given that we've had warmer periods in the past, we should not exist.

But the fact remains - no one knows what more clouds mean.

Bob Hawkins writes:

> But the real danger isn't the carbon dioxide, it's the water vapor - the additional heat from carbon will cause more water to evaporate, increasing the water vapor in the air. Water vapor is the most powerful/ubiquitous greenhouse gas

Precisely. Global warming hysteria is based entirely on the assumption of a large positive water vapor feedback.

If there is a large positive water vapor feedback, one effect would be increased Antarctic precipitation. The interior of Antarctica is cold enough to freeze out practically all of the water vapor in the air above it. If the air contains more water vapor, there will be more Antarctic precipitation. But there isn't. ~QED.

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