Skeptic screed on progressive news site recycles familiar myths
This post was co-written with David Roberts.
Word is that this was an editorial slip-up on HuffPo’s part; they don’t typically provide a place for this kind of agitprop. The essay is gone from the site’s portal pages and rumor has it The Huff herself may address the issue soon.
Regardless, the essay is out there getting skeptics all twitterpated (again). These folks can’t find a scientific journal with two hands and a flashlight, but nothing escapes their RSS feeds.
So lets examine a few of the claims again. After all, the only thing hucksters need is for the rest of us to get tired of repeating the same damn truths over and over again. Right?
Right off the bat Mr. Ambler recycles a classic, one of the most durable and thoroughly discredited skeptic chestnuts:
Because it turns out that there is an 800-year lag between temperature and carbon dioxide [in the ice age record], unlike the sense conveyed by Mr. Gore’s graph. You are probably wondering by now — and if you are not, you should be — which rises first, carbon dioxide or temperature. The answer? Temperature. In every case, the ice-core data shows that temperature rises precede rises in carbon dioxide by, on average, 800 years.
The basic science of atmospheric carbon dioxide is well explained in the IPCC reports and on numerous web sites, including in Grist’s How to Talk to a Skeptic series. It’s puzzling that it continues to confuse skeptics.
The claim that the CO2 rise begins after the temperature rise is correct but misleading. The cause of the ice ages is well known: slight shifts in the Earth’s orbit. Those shifts, however, are too weak to explain the full temperature swings seen during ice ages. That’s where carbon dioxide comes in. It acts as a feedback, taking the small effects of orbital changes and turbocharging them into the enormous temperature swings observed in the historical record.
So yes, carbon dioxide plays a key role in ice ages. Arguing otherwise demonstrates a lack of understanding of even the most rudimentary climate physics.
When the ocean-atmosphere system warms, the oceans discharge vast quantities of carbon dioxide in a process known as de-gassing. For this reason, warm and cold years show up on the Mauna Loa CO2 measurements even in the short term. For instance, the post-Pinatubo-eruption year of 1993 shows the lowest CO2 increase since measurements have been kept. When did the highest CO2 increase take place? During the super El Niño year of 1998.
Check out this plot of the Mauna Loa carbon dioxide record and tell me if you see any effect of ocean temperature in 1993 or 1998:
No? Who you going to believe, Mr. Ambler or your lying eyes?
In fact, there’s no question that humans are responsible the atmospheric abundance of carbon dioxide. The strongest evidence comes from measurements of the isotopic signature of carbon dioxide — the amount of carbon-12, -13, and -14 in the atmosphere. Carbon dioxide from fossil fuels has a unique signature not shared by biomass or volcanoes. This is well described in the IPCC reports and in this RealClimate post among other places.
Meanwhile, the theory that carbon dioxide "drives" climate in any meaningful way is simply wrong and, again, evidence of a "flat-Earth" mentality. Carbon dioxide cannot absorb an unlimited amount of infrared radiation. Why not? Because it only absorbs heat along limited bandwidths, and is already absorbing just about everything it can.
It is true that the forcing due to carbon dioxide is proportional to the logarithm of the concentration. Mr. Ambler takes that fact and concludes that we are therefore at the maximum forcing from carbon dioxide. Say what? While individual spectral lines do indeed saturate, adding more carbon dioxide pushes the level of saturation higher in the atmosphere — leading to additional heating of the surface.
Evidence of this can be found on Venus, which has a surface temperature of 450°C — hot enough to melt lead; hotter even than Mercury, which is closer to the sun. Why so hot? Venus has a thick, carbon-dioxide-rich atmosphere, which Mercury does not. If, as Mr. Ambler claims, carbon dioxide saturates, Venus’ temperature ought to be lower than Earth’s, owing to the thick sulfuric acid clouds that shroud the planet and reflect sunlight. It’s not; Mr. Ambler does not know what he’s talking about.
Further, the IPCC Fourth Assessment, like all the ones before it, is based on computer models that presume a positive feedback of atmospheric warming via increased water vapor. … This mechanism has never been shown to exist.
This is another skeptic zombie that just won’t stay killed. It could not be more wrong if Sarah Palin herself said it.
In fact, one of us (hint: not the blogger) recently published a paper estimating the magnitude of the water-vapor feedback exclusively from data — no climate models involved. Sure enough, the water vapor feedback is strong and positive. There are several other observation-based analyses that agree with this conclusion (see references in the paper).
By the way, water vapor is far more prevalent, and relevant, in the atmosphere than carbon dioxide — a trace gas. Water vapor’s absorption spectrum also overlays that of carbon dioxide. They cannot both absorb the same energy!
To give Mr. Ambler some credit, this was the subject of legitimate scientific uncertainty … in the first half of the twentieth century. However, careful spectroscopic measurements settled it about 50 years ago. There is indeed some overlap, but enough lines do not overlap that carbon dioxide is indeed an important greenhouse gas.
Indeed, the case against carbon dioxide is pretty close to airtight — see, e.g., this old post.
Finally, Mr. Ambler shares his theory of why the climate is warming: it’s everything other than carbon dioxide! It appears the climate science community has gotten it as wrong as those kooky tobacco alarmists.
Notwithstanding Mr. Ambler’s confusions and deceits, humans are now in the climatic drivers’ seat, with the pedal to the metal. Maybe it’s time we put our hands on the wheel.
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