Personally, I think [and will not tolerate any opposition to this as I may be allowed to think as I please - although I'm aware of people positing otherwise] that Venus shows that CO2 is an important greenhouse gas and that this is also true on the Earth, although the effect of, say, a doubling of CO2 is not known. Similarly, variations of the Sun [if any can be found] may also have an effect, but again, of unknown [small] magnitude. Since most of the heat is stored in the oceans, on simple physical grounds one would expect to look there for influence on the climate. Finally, ‘external’ factors [such as orbital changes, impacts, super volcanoes - should Yellowstone blow, for instance] will overwhelm whatever small effects ensue from the ‘usual suspects’.

Leif, I, for one, appreciate you taking the time to give us your perspectives on the issues of importance to you.

However, I don’t think CO2 is important unless you start getting to extreme levels. I mean, how does Venus’ CO2 concentration compare to that of Earth? Millions of times higher? How many doublings would it take to get there, and how long, at the most liberal estimate, would it take to get even halfway there?

I still don’t believe we can learn anything from Venus with our current knowledge. We’d need to study it, on the ground, at least as much as we’ve studied the Earth to have any kind of certainty about its past. Anything outside of our direct observations are just WAGs, not even SWAGs. IMHO.

Possibly not, but the same can be said, IMHO, about any and all of the other hotly debated issues, theories, SWAGs, and other surmissions. As long as politics, ‘greenness’, save-the-planet panic, emotional attachments, cap-and-tax ideas, and all the rest are dominating the discussion over the little science we know, we cannot make any societal decisions with good conscience, but will have to let each person for himself/herself act according to own judgment.

Personally, I think [and will not tolerate any opposition to this as I may be allowed to think as I please - although I'm aware of people positing otherwise] that Venus shows that CO2 is an important greenhouse gas and that this is also true on the Earth, although the effect of, say, a doubling of CO2 is not known. Similarly, variations of the Sun [if any can be found] may also have an effect, but again, of unknown [small] magnitude. Since most of the heat is stored in the oceans, on simple physical grounds one would expect to look there for influence on the climate. Finally, ‘external’ factors [such as orbital changes, impacts, super volcanoes - should Yellowstone blow, for instance] will overwhelm whatever small effects ensue from the ‘usual suspects’.

What I rail against is the tendency to ascribe all climate change to just one thing, AGW, the Sun, GCRs, etc. , and to cherry-pick data [of which there is plenty of every stripe] that happens to support one’s view. I realize that once you adopt a more nuanced view, so many % due to this, and so many % due to that, and so many % due to something else, then the politics falls by the wayside [to quote Dubbya Shrub "you are either with us or with the enemy" - or think of various religions that all have a monopoly on the truth] and that that is the main problem that stands in the way of a rational exploration of the issue, because the proponents of the various camps do not allow this more nuanced view: it is all or nothing.

I have tried to mainly stay with what I know something about and thus not discuss ocean circulation, atmospheric modeling [although I did some of that long ago, but that was primitive compared to today], land-use issues, temperature adjustments, etc. Many of the things that are bread-and-butter solar physics also happen to be important [or thought so by various people] in climate research, such as radiative transfer in gases, atmospheric circulation and heat flows, spectra, cosmic ray physics, and much more, so I occasionally spill over into these areas when I think I can clarify a detail or two.

On this journey I have both been encouraged by people that have expressed appreciation for my comments [which BTW takes considerable time and effort] and been dismayed by the few bad apples that always frequent fora like this, but on the whole my experience has been enjoyable [which is why I'm writing this right now] as I have always felt satisfaction from sharing knowledge and interacting with people that are serious about learning. Your questions have often been an inspiration to me and have often made me think about issues that I would not normally have done, and so have contributed to widening my own horizon.

Lief,

The conclusion, as a scientific endeavor, is obvious. However, it does not scale to significance to the current AGW debate.

This has turned into a delightfully informative discussion. But, can anyone here cite one Venusian fact or theory significant to dealing with environmental and subsistence issues facing our great grand children?

why is the pressure at Venus surface 92 times that on Earth?
Because all the CO2 that were in the rocks is now in the atmosphere. If you put all the CO2 sequestered in the Earth’s rocks into the atmosphere, it too much be about as thick.

Surely, under that pressure and temperature, the atmosphere would blow away? And if the atmosphere can’t blow away, then surely the pressure will create heat?
The pressure at the surface is the weight of all the material [CO2] above it, so you have a crushing weight [1500 pounds per square inch] holding down the atmosphere, that’s why it doesn’t blow away. And constant pressure does not generate heat, if it did, then surely the atmosphere would blow away, but so would the planet itself and the Earth too as the pressure of 4000 miles of rock is truly gigantic.

I understand that Venus is very volcanically active so the CO2 and Sulfer is being constantly replaced, but won’t that add to the pressure that the gas is under?
Although there seems to be 1600 volcanoes on Venus there is great doubt as to any of them is active. In perhaps one case some ash has been observed. Some variations of the trace elements [sulphur dioxide] have been observed, but it is not known if that was due to volcanic activity or to processes in the atmosphere. The ‘hunt’ is on to find an active volcano, but so far no luck, so we cannot say that Venus is volcanically very active.

At http://www.universetoday.com/guide-to-space/venus/does-venus-have-volcanoes/
you will find:
But does Venus have any volcanoes right now? Unfortunately, we just don’t have enough data to go on. Venus is shrouded in thick clouds of carbon dioxide in its atmosphere, so you can’t have an orbiter easily take photographs of the planet’s surface.
There is no water on the surface of Venus, and scientists know that the planet has no plate tectonics, like we have here on Earth. There are no continents. And so Venus doesn’t have the same regions of volcanism as we have on Earth. So right now, scientists have no idea if there are volcanoes on Venus. There could be a few spotty regions across the planet, where there is some activity, but none have been seen erupting in the present.

I’m sure you’re right about adiabatic heat leaking away, but sometimes a big cloud of gas and dust gets together and gravitational forces pull the gas together and sometimes the pressure gets so great that the gas molecules fuse together and generate even more heat which causes more fusion and before you know it, you have a runaway fusion effect and a star is born.

Now I realise that interstellar gas is pulled together by gravity and the pressure is constantly increasing, which might combat the fact that the adiabatic heat is dissipating, whereas on Venus… Well why is the pressure at Venus surface 92 times that on Earth? Surely, under that pressure and temperature, the atmosphere would blow away? And if the atmosphere can’t blow away, then surely the pressure will create heat?

I understand that Venus is very volcanically active so the CO2 and Sulfer is being constantly replaced, but won’t that add to the pressure that the gas is under?

I don’t doubt that there is a greenhouse effect on Venus, but I’m not quite ready to give up on the pressure theory yet.

No, what McIntyre (and others) have to do is either show (preferably in a professional manner ) where the large body of studies are wrong in their methods or conclusions or else produce his own estimate for climate sensitivity and present it for review. So far he has done neither.

He’s done exactly that with respect to the hockey stick and the way many studies have used the same denrochronology data. They’re basically making crap up.

George Landis has a good paper on Venus here:
http://gltrs.grc.nasa.gov/reports/2003/TM-2003-212310.pdf

He writes:
“In the early solar system, about four billion years before present, the sun was approximately twenty-five percent less luminous than it is today. Under these conditions, it is plausible to suggest that Venus was much more Earthlike than it is today. As the solar luminosity increased, Venus became trapped in a runaway “moist greenhouse effect.” [3] The rising temperature increased the evaporation of water vapor from the oceans; this increased water vapor in the atmosphere increased the trapping of infrared radiation, which increased the heating of the planet. Eventually this feedback loop resulted in the oceans boiling dry (and hence releasing very large amounts of greenhouse gas into the atmosphere), and shortly thereafter any surface carbonate rocks decomposed into the primary minerals plus carbon dioxide, releasing their carbon dioxide back into the atmosphere. The thick carbon dioxide atmosphere and intense greenhouse effect results in the high atmospheric pressure (about 90 bar) and high temperature (approximately 450C) found on the surface of Venus now”
and concludes that:
“Venus is the best laboratory in the Solar system for study of the greenhouse effect. If we are to understand climate change on Earth, we can learn by comparing and contrasting the history and climate of the Earth with that of its nearby neighbors, Venus and Mars.”

Steve McIntyre is doing what he knows how to do. He is auditing. That is what he does. There are not many people watching what is happening in the cozy climate science community, but because of the efforts of McIntyre, our host here, and a few notable others, the truth is getting out.

It is my understanding that gas under pressure heats up. When the molecules of gas are forced together the get all excited and they show this exitement as heat. How much of Venus high temperature is down to adiabatic heat caused by the 92 bar pressure at ground level? One datum that points to this might be the fact that there is a layer of Venusian atmosphere where the pressure is earth-like and the temperature is earth-like.

Much is sometimes made of the high ‘dark-side’ temperatures on Venus. The Venusian day is very long, but there are 300mph winds on Venus which are pretty good at distributing the heat. The winds are faster than the day-length and circulate in the opposite direction.

The clouds of sulfuric acid mention above are such good reflectors of solar energy that it is reckoned that the amount of this energy that reaches ground level is about the same as on Earth. These clouds though are pretty good ‘blankets’ which trap the heat, including the adiabatic heat, in Venus atmosphere.

All in all, I would have to agree with those commenters above who say that attempting to draw conclusions about Earth’s climate from Venus is misleading to say the least.

So, the Great Venus Debate is based on a misunderstanding, it seems. But it did expose some of the skewness of the whole issue. The crowd that denies CO2 having any effect on the Earth going so far as to deny it has any effect on Venus either, even ascribing the heat instead to H20 in spite of Venus being ‘bone dry’ [H2O only existing as a trace component with highly variable minute concentrations].

The description [Dee] of how the Water got lost is marred by the use of the present tense instead of the past tense:
“So, as water rises in Venus’ atmosphere and reaches this region, UV light dissociates it into two hydrogen atoms and one oxygen atom. The hydrogen is much lighter than the water molecule was, and so it easily escapes Venus’ atmosphere.”
And of this gem:
“The water will usually quickly recombine with a carbon or carbon monoxide molecule to form carbon monoxide or carbon dioxide. “.
Somehow suggesting that the water is recycled ['recombine']. But the water is gone, it is the oxygen that combines with carbon.

When the Venusian oceans disappeared billions of years ago, the run-away greenhouse effect was obviously a combination of both CO2 and H2O with H2O even being the main culprit. Both that was a very long time ago and the heat trapped then is not what is around today. As Wikipedia correctly points out: “In the absence of the greenhouse effect caused by the carbon dioxide in the atmosphere, the temperature at the surface of Venus would be quite similar to that on Earth”.

To the question of which came first, the heat or the CO2, the answer is BOTH. Venus never had a biosphere to reduce the original CO2 atmosphere and has always received about 300% more solar energy.

When you read that billions of years ago, Earth and Venus had similar atmospheres, that is correct, but life developed on the Earth and ultimately converted the CO2 to the very corrosive (and poisonous to life) O2. [In doing so, life nearly wiped itself out which resulted in the formation of the 'modern cell' and the ability to burn sugars with O2 for the energy needed to convert ATD back to ATP - but that is another story - see below.] Venus, burdened with the additional solar energy, never developed ‘life’ and therefore never purged the primal CO2 from the atmosphere. And so it goes.

As a biology related aside, the process used by plants to make sugar is fairly complex as a result of the absorption of the chloroplasts, but despite the common meme that plants convert CO2 into O2, the truth is more complex and interesting. Basically the plant uses the CO2 to form a sugar by combining with H liberated from H20. Two O radicals combine to form 02. During this process, some of the energy captured from the Sun by the chloroplasts is used to convert ATD to ATP.

As alluded to earlier, animals burn this sugar with O2, convert ATD to ATP and release CO2 and H20.

Sugars are hydrocarbons as is oil. In any clean burning process using hydrocarbons, the only ‘waste’ products should be CO2 and H2O.

I find myself continually humbled by the complexity and grandeur of the world.

Well, I have directed you towards numerous studies, both paleo- and modelled that indicate that the effects of the feedbacks after a doubling of CO2 is in the range stated. The earliest of these is nearly three decades old and so has stood up to that amount of scrutiny.

The major feedback is the increase in water vapour, and an interesting confirmation that the models treat the water vapour feedback correctly came after the eruption of Pintubo. This caused a significant and measurable global cooling and enabled a valuable planet-wide experiment – was the resulting drying of the atmosphere consistent with that predicted by the models? Here’s the answer.

McIntyre is engaging in little more than a rhetorical trick – ask a question then continually declare yourself dissatisfied with the answers. His complaint is the lack of a ‘proof’ of the feedback estimates in the literature, when the method by which climate sensitivity is calculated is actually laid out in detail in the IPCC reports and supporting papers. (WG1 Chapters 9 & 10. )

(As an aside, Viscount Monckton claims to have discredited the IPCC climate sensitivity calculations in his APS <a href=”http://www.aps.org/units/fps/newsletters/200807/monckton.cfmpaper” paper, whereas Steve McIntyre claims not to be able even to find these calculations. Can anyone explain? ).

The second half of the trick is to take the normal conservative language used in science and emphasise and exaggerate the discussions of the uncertainties that exist, then complain about lack of ‘engineering quality’ or ‘proof’. This, of course, is a misunderstanding of basic scientific reality. Science deals in the balance of evidence, not proof; there are not two categories of science – ‘settled’ and ‘not settled’, there are degrees of certainty.

No, what McIntyre (and others) have to do is either show (preferably in a professional manner ) where the large body of studies are wrong in their methods or conclusions or else produce his own estimate for climate sensitivity and present it for review. So far he has done neither.

JP.

Venus’ atmosphere is nearly 100 times as massive as Earth’s, and its thick cloud layers block the surface from view. It exerts a pressure of approximately 92 bars at the surface. Its composition is nearly all CO2.

Venus is the case of a runaway greenhouse effect. The temperature and pressure of the atmosphere decrease with height, so water vapor rises in the atmosphere and encounters conditions that cause it to condense back into liquid water and fall back to the surface – a region called the “cold trap.” On Earth, this is at a height of 9-15 km (5-9 miles) above the surface, but on Venus it lies at an altitude around 50 km (31 miles) due to the planet’s closer proximity to the sun.

On Earth, the ozone layer is several kilometers above this, and the ozone prevents ultraviolet light from destroying water in our atmosphere. On Venus, there is no ozone layer, and the atmosphere doesn’t become opaque to ultraviolet light until a depth is reached below the cold trap. This allows ultraviolet light to destroy water between this height and the cold trap’s.

So, as water rises in Venus’ atmosphere and reaches this region, UV light dissociates it into two hydrogen atoms and one oxygen atom. The hydrogen is much lighter than the water molecule was, and so it easily escapes Venus’ atmosphere. The water will usually quickly recombine with a carbon or carbon monoxide molecule to form carbon monoxide or carbon dioxide. This is probably one reason why there is so much carbon dioxide in Venus’ atmosphere today.

Heavy water, however, which is composed of one oxygen, one hydrogen, and one deuterium (a proton and one neutron), cannot reach the requisite height as easily. If it does, it can still be dissociated just like normal water, but this happens at a much slower rate. Thus, a measurement of how much deuterium compared with how much hydrogen today shows that Venus has much more deuterium in its atmosphere for each hydrogen atom than Earth does. This is the strongest evidence that Venus has lost a massive amount of water in its history.

This process is a runaway one in that once less water is available to wash CO2 from the atmosphere, the CO2 level rises. This results in a stronger greenhouse effect, so the temperature rises. The higher temperature moves the cold trap higher, and the cycle continues at an accelerated rate because there is a larger region where water can become dissociated.

From: http://burro.astr.cwru.edu/stu/venus.html