Guest Post by Willis Eschenbach
Over at Dr. Judith Curry’s always excellent blog, she has a post headlined by a question, viz:
What are the main sources of heat that account for the incremental rise in temperature on Earth?
Let me start by saying that this is a horribly phrased question. Consider a parallel question:
What are the main sources of heat that account for the incremental rise in my body surface temperature when I put on a jacket?
I’m sure you can see the problem with Dr. Judith’s question—temperatures can rise without ANY new sources of heat or ANY change in existing sources of heat.
For example, regarding the climate system, every year there is more and more oil that goes into the ocean. This oil floats on the surface in a monomolecular layer, and it reduces both conduction and evaporation. As a result, the oceans end up slightly warmer than they would be without the oil … where is Dr. Judith’s mysterious “source of heat” supposedly driving that change?
Here’s another example. Over say the last 50 years the incremental temperature rise at the Poles has been generally greater than in the tropics. This reduces the equatorial-polar “delta-T” (∆T), the temperature difference between the two. But wind speed is generally some function of ∆T, so less ∆T means less wind. And evaporation is linearly proportional to the wind speed, so this would tend to amplify warming from whatever cause by reducing evaporation … and where is the “source of heat” for that wind-related amplification of warming?
With that as a preface, let me start by giving you an overview of our understanding of the historical climate. Be forewarned, it’s depressing. Here we go.
Nobody knows why the Roman times were generally warmer than times prior to that, or why it generally cooled after the Roman Era.
Nobody knows why it then warmed again up to the Medieval period.
Nobody knows why the warmer Medieval times were followed by fairly rapid cooling to the Little Ice Age of the 1600s-1700s.
There’s more. Nobody knows why the Little Ice Age didn’t turn into a real ice age. Certainly, the orbital parameters were there for us to slip into a glacial period … but it didn’t happen. Why? We don’t know.
Instead, and again for reasons nobody understands, rather than continuing to cool, the planet started warming, at about a half a degree per century for the last few centuries, right up to the present.
(Please note that “nobody knows” doesn’t mean “nobody claims to know”. I can find ten scientists tomorrow who all claim they know why the Little Ice Age came about … the problem is, they all have different answers. But the truth is … nobody knows.)
And as far as we can tell … none of those gradual temperature changes were caused by variations in CO2.
Given all of that, it is a giant and unsupported leap to think that we can say either that a) there’s been an increase in some kind of heat source, or b) whatever might have caused that increase in the heat source, it has in turn been the cause of the recent years of incremental warming.
I gotta say, the hubris of climate scientists is beyond all bounds. Despite not being able to explain the past, they claim that they can predict the future out a hundred years … pull the other leg, it has bells on it …
But heck, let’s pretend for a moment that in some mysterious fashion we’ve been able to establish firmly that the change in surface temperature is indeed caused by a corresponding increase in radiation absorbed by the surface. Here’s a graph of the anomalies in total absorbed radiation at the surface (longwave plus shortwave, blue) along with the total absorbed solar radiation anomaly (shortwave only, red).
I’m sure that you can see the problem. The change in just absorbed solar radiation alone is more than enough to explain the entire change in total absorbed radiation at the surface …
So per this particular individual analysis of the CERES data, the source of energy for the incremental change in temperature is … the sun. No need to invoke CO2 or GHGs of any kind. The sun alone provided enough additional heat to completely explain the total increase in absorbed radiation.
Now, does this show that the sun is indeed the cause of the gradual warming? ABSOLUTELY NOT. There are plenty of forces at play in even this restricted subset of climate variables, and the fact that a couple of them line up does NOT mean that one is causing the other.
Part of the problem is our childlike insistence that there is some kind of simple cause-and-effect going on in the climate. I describe it instead as a “circular chain of effects”. Here’s an example. The sun warms the ocean. The warmer ocean generates more and earlier daily clouds. The clouds cut down the sun. Less sun makes the ocean cooler. The cooler ocean produces fewer and later daily clouds … you see the circle, you see the problem.
There’s an insightful Sufi teaching story about this question. Hussein asked the Mulla Nasruddin:
“Well, then, how do you account for cause and effect?”
Nasruddin pointed to a passing procession carrying a coffin and said:
“They are taking a hanged man, convicted of killing another man, from the gallows to the grave. Is this the result of his stealing the knife from the butcher, or of using the knife to murder his enemy, or of being caught by the police, or of his being prosecuted by the magistrate, or of being found guilty by the judge, or of being hanged at the gallows? Which event can you point to and say ‘This is the moment in time that caused him to meet his fate’?”
But then, as Nasruddin was wont to say, “Only a fool or a child looks for both cause and effect in the same story” …
Anyhow, in answer to Dr. Judith’s question, I fear that all we can say with certainty is …“Nobody knows”.
My best to everyone on a lovely winter night,
PS—As usual, I politely request that when you comment you QUOTE THE EXACT WORDS YOU ARE REFERRING TO, so we can all understand what you are discussing. Please note that although the request is polite, if you ignore it, I may not be … I’m tired of picking random unsourced uncited unreferenced spitballs off the wall.
PPS—In addition to the always-fascinating scientific give-and-take here, let me invite you all to contribute to the ongoing discussions of a more political and personal nature at my own blog, Skating Under The Ice, or to follow me on Twitter, @WEschenbach.