A science presenter, writer, speaker & former TV host; author of The Skeptic's Handbook (over 200,000 copies distributed & available in 15 languages).


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New Science 7: Rerouting Feedback in Climate Models

Conventional models assume increasing atmospheric CO2 warms the surface, then apply the feedbacks to the surface warming. But if feedbacks start up in the atmosphere instead, everything changes.

This is a post with big potential. A feedback the other climate models miss?

All the establishment models assume carbon dioxide warms the sky, which leads to the surface warming*, and the feedbacks then apply to the surface warming. It’s in the model architecture, the models can’t do it any other way. But what if the feedbacks don’t wait — what if the feedbacks start right away, up in the atmosphere? What if, say, CO2 warms the air, and that affects humidity and or clouds right then and there? These would be feedbacks operating on tropospheric warming, and they can reroute that energy.

Potentially, this blows everything away. If the energy blocked by increasing CO2 is merely escaping Earth through emissions from another gas in the atmosphere, like say, the dominant greenhouse gas, water-vapor, then could this explain why the effect of Co2 has been exaggerated in the conventional models?

We call this the “rerouting feedback” because when it’s harder for energy to escape to space through the CO2 pipe, this [...]

New Science 6: How the Greenhouse Effect Works and “four pipes” to space

The Earth’s atmosphere is a leaky bucket, with four big holes (and a lot of little ones).

Whole libraries have been filled with talk of a single characteristic emissions layer — a simplistic idea that there is one effective “surface” that radiates to space. It exists in an abstract sense, after sufficient averaging, but it’s a paradigm that doesn’t help us think clearly. In any case, it’s too simple for our purposes in this series. In reality there are many layers that radiate to space, different for each type of molecule that can emit longwave radiation (which means infrared). Then there are the surface and cloud-tops too.

Energy comes in one way but leaves through at least four different paths.

To follow this series you’ll need to understand the concept of four pipes through which energy flows to space. It’s a powerful idea and big advance on the simpler notion of one-pipe-in and one-pipe-out. For those not as familiar with photons and excited molecules, you may want to read the “Background” section at the end of the post first.

For a photon there are a lot of paths to space

Some photons at Earths surface will be at the [...]

A discussion of the Slaying the Sky Dragon science: Is the Greenhouse Effect a Sky Dragon Myth?

 ”Skeptics” are described as if they are one small block of  fringe extremists, but not only is half the population skeptical in some sense, in this debate I am not on either extreme, but a centrist, smack in the middle. On the one hand, alarmists are convinced the climate is headed for a catastrophe, and on the other some people are convinced there is no greenhouse effect at all. Wes Allen, sits in the middle with me, and he’s been engaged in an intense debate with people on both ends of the spectrum. After a scorching critique of Tim Flannery’s work, he has swung his attention the other way. Here is his synopsis of the Slayers book, for discussion, and I’m sure it will generate a long passionate defence and debate, just as previous posts on this topic have. (eg: Why greenhouse gas warming doesn’t break the second law of thermodynamics and So what is the Second Darn Law?). I know the Slayers are keen to discuss their ideas. I’m hopeful people can remain polite, as that’s where progress may be made… many thanks to Wes here who has done a diligent write up, and has gone to great [...]

Do greenhouse gases warm the planet by 33°C? Jinan Cao checks the numbers.

Jinan Cao has been dissecting the nature of the greenhouse effect and a key calculation that I normally just accept without questioning. This will set a few pigeons loose, but it will be interesting to see where they land. The claims analyzed here are the oft repeated ones that the Earth’s greenhouse effect already warms us by 33°C and that a doubling of CO2 directly causes a 1.1°C rise (that’s with no feedbacks taken into account).

Jinan points out that these numbers, repeated as “fact”, are merely a result of misuse of the Stefan-Boltzmann equation. If Earth is not a perfect black body, but has an emissivity of 0.7 (as satellites suggest), then the temperature of the planet’s surface without any greenhouse effect would not be -18°C, but more like 5°C. That would mean the entire warming due to the greenhouse effect is only around 10°C, not the more impressive 33°C that is usually claimed. It means the greenhouse effect is probably less important than implied.

The 1.1°C direct rise that is predicted from doubling CO2 without feedbacks would also need to be recalculated. This paper does not try to do that, but if Jinan is right, that figure would [...]

There is a Greenhouse Effect on Venus

I‘m peppered with emails asking me if articles like this one (which claims there is no Greenhouse Effect at all on Venus) could be right.

Michael Hammer has some 20 patents in spectroscopy, and he explains why the Greenhouse Effect — where CO2 and other gases absorb and emit infra red — is very real, and backed by empirical evidence. The calculations using the Stefan-Boltzmann Law on the atmosphere of Earth and Venus, argue that the Greenhouse Effect is not-detectable. But not-detectable (by that method) does not “prove” the effect is zero. Other methods — like satellite observations of Earth’s atmosphere, and countless lab experiments, tell us that the Greenhouse Effect is real. (The Stefan-Boltzmann Law is used to create the first graph below). Huffman’s calculations suggest other factors are more important than greenhouse gases (with which we heartily agree) and that Hansen et al were barking up the wrong tree by pretending that Venus “shows” us anything much about the Greenhouse Effect. (Indeed, the IPCC mention “Venus” in their first Assessment Report back in 1990 as one of the three key reasons.)

So here in middle-of-the-road centrist land, the people who claim Earth could become more like Venus are [...]

So what is the Second Darn Law?

With nearly 500 comments on the thread on the Second Law of Thermodynamics there is obviously a need for people to discuss the basic greenhouse theory. Here’s a new thread on that theme.

So what is the Second Darn Law?

From NASA:

But there are variations

As with all these Laws of science there is no exact wording, because There Is No God Who Issues Science Decrees*.  What we have are human efforts to best explain the world around us. Note that the two well known versions of the Second Law both contain the phrase “whose sole result”, meaning that heat transfer can certainly move from a colder to a warmer body if there is some other compensating movement where more heat is transferred from a hotter body to a colder one. Voila… whatever heat transfer goes from greenhouse gases to the Earth is more than countered by the heat moving from the Sun to Earth and on to space. Greenhouse gases can heat the Earth as long as the entropy of the whole system increases.


Why greenhouse gas warming doesn’t break the second law of thermodynamics

This is generating many comments, see below for an update!

Behind the scenes some skeptics are suggesting that CO2 can’t warm us because the atmosphere is colder than the planet, and  it would break the 2nd Law of Thermodynamics (see Postma*, for example, p 6 – 7). I disagree. The 2nd Law of Thermodynamics applies to net flows of heat, not to each individual photon, and it does not prevent some heat flowing from a cooler body to a warm one.

Imagine three blocks of metal side by side. They are 11°C, 10°C, and 9°C. Think about what happens to the photons coming off the atoms in the middle of the medium temperature block between the other two. If heat never flows from cooler blocks to warmer blocks, all those photons have to go “right“, and not ever go “left”, because they “know” that way is towards a cooler block? (How would they?!)

The photons go both ways (actually every way, in 3D). There are more coming from the 11°C block to the 10°C block, sure, but the the 10°C block is sending ‘em back to the 11°C block too. So heat is flowing from cold to hot. It happens [...]