Saturday, June 13, 2009

The “runaway greenhouse effect”: James Hansen vs Gavin Schmidt

References to "tipping points" and the specter of a "runaway greenhouse effect" or "runaway global warming" can be found EVERYWHERE in AGW alarmist writings. It’s on blogs, it’s in the news and, most importantly, some of the most prominent climate scientists invoke it. There’s no denying it’s a favourite bogey-man and scare tactic.

On the other hand many AGW true believers know full well that predictions of a runaway greenhouse effect are over-the-top alarmism with little theoretical or evidentiary basis. On occasion an AGW skeptic will point to evidence that shows such predictions are unfounded. The response of the AGW huckster is to berate the skeptic for bringing the subject up and to deny anyone thinks it a problem.

An example of the latter can be found in this RealClimate comment thread:

Comment by Don Healy (19 August 2008 at 11:31 AM) : [...] ... Another question that comes to mind is if earth did not experience a runaway greenhouse effect when CO2 levels were 4000 ppm or higher in earlier geologic history, what has changed to create such alarm at levels ten times lower? Just some random thoughts from one whose background is in forestry and plant physiology.

[Response: No one is predicting a runaway greenhouse effect in that sense (this is one of those trivial talking points alluded to the post). ... Please be serious. - gavin]

Note: "gavin" is Gavin Schmidt, a climate modeler at NASA/GISS and co-founder of the RealClimate blog along with Michael Mann et al.

An example of the former (alarmism) is in this article featuring prominent climate scientist alarmist James Hansen (Director of Research at NASA/GISS and, presumably, Gavin Schmidt’s boss) shrieking about a runaway greenhouse effect:

"If we burn all of the coal [on the planet], there is a good chance we will initiate the runaway greenhouse effect," he said. That runaway greenhouse effect could become unstoppable, eventually boiling the oceans and destroying all life on earth in what Hansen called the "Venus Syndrome," after the conditions that exist on the planet next-closest to the sun.

"We already probably have CO2 past the tipping level that would cause some effects like the loss of arctic sea ice,"

So we have two colleagues (boss and underling) at the same government organization positing two wildly different views about a runaway greenhouse effect. Though Gavin Schmidt sensibly downplays the credibility of the notion of runaway global warming he’s absolutely wrong when he says no one is predicting it - his boss is, for one. And Schmidt weasel-worded his reply saying no one is predicting it "in that sense". If not "that sense", what sense? He doesn’t say, but perhaps he means the sense that his boss, James Hansen, is using - the alarmist propaganda sense.

7 comments:

Halfwise said...

Runaway alarmism about global warming is "worse than the models predicted" and we are already at or near or past a "dangerous tipping point", fated to endure increasingly shrill sanctimony.

Said growing shrillness will occur in direct proportion to the mounting evidence that the whole AGW era has been either a hoax, mass delusion or terrible misunderstanding based on the available evidence. Sadly, the "precautionary principle" will remain enshrined in our consciousness as something with actual merit, like a proven vaccine. We can look forward to more H1N1 panic-demics and Y2Ksterias because, although the "scientists" were profoundly wrong, they had only our best interests at heart.

JR said...

True. Nevertheless, in the AGW "debate" there is, now and again, a sign that things are changing for the better.

Michael Ejercito said...

These runaway tipping points assume that humanity would just do nothing about runaway global warming.

If nothing else, we would detonate a few dozen hydrogen bombs as a countermeasure.

Spin Assassin said...

Runaway Greenhouse effect is one of the most hilarious doom prophecies ever. Venus's atmosphere is a product of being too close to the sun. DUH! The fact that many warm ages have come and gone with CO2 levels 20 times higher than we have today without ending all life on Earth pretty much slams the door on the Runaway Greenhouse effect.
What is even funnier is when some warmists propose that there are no aliens in the sky because Global Warming boiled them all. You can add Intergalactic Genocide to the trumped up charges against an industrial society. It gives me no end of pleasure to imagine the impending headline: Global Warming Killed the Aliens. LMAO

Anonymous said...

Does anyone here actually have substantive understanding of the physics? Blackbody equilibrium temperature, the Steffan Boltzman equation, the atmospheric transparency to visible light, the opacity to infrared, etc. Venus has a surface temperature of around 900F despite having a effective blackbody equilibrium temperature of only about 135F. So, DUH, it's surface temp is not because it is too close to the sun. Unless you really can quantitatively deal with these subjects, and more, you are just ranting in ignorance.

Kaboom said...

Anonymous, it is so refreshing to discourse with someone who appears to understand the physics of the Venusian "Runaway Greenhouse Effect".

As you no doubt know, the Venusian atmosphere is composed 96.5% of CO2, with the remainder being nitrogen, with trace amounts of sulphuric acid, chlorine and fluorine compounds.

You would also be aware that Venus has an atmospheric density of approximately 92 bar, or 92 times greater than Gaia's atmospheric pressure.

Following me? Good.

The surface temperature is, as you rightly point out, not dependant upon the amount of sunlight, but it is an artefact of the pressure of the atmosphere.

Here is your homework.

Assuming the surface temperature of Venus is ~480C (~900F), replace the Venusian atmospheric components with that of Gaia (78% Nitrogen, 21% Oxygen, 1% others (primarily Argon)).

Calculate the expected surface temperature of Venus at 92 bar with Gaia'a atmospheric mix, assuming solar irradience of 2,614 W/m2.

If you are a good student, you will conclude that the surface temperature of Venus would actually increase by 200C, wouldn't you?

Nothing like ranting in ignorance, is there?

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Greenhouse effect is the gradual warming of the air surrounding the earth as a result of heat being trapped by environmental pollution.