I guess I shouldn’t have been surprized at this, but still……
This rediculous essay by Steve Goddard attacks the well known runaway greenhouse effect on Venus. I’ll post statements on the other blog entry in red and my direct responses in blue.
The classic cure for hyperventilation is to put a paper bag over your head, which increases your CO2 levels and reduces the amount of Oxygen in your bloodstream.
Global warmers have been hyperventilating over CO2 on Venus, ever since Carl Sagan made popular the idea of a runaway greenhouse effect. That was when he wasn’t warning about nuclear winter. Sagan said that marijuana helped him write some of his books.
Ad hominem attack. I guess cheap shots by proxy against accomplished scientists long dead are what Anthony Watts is reduced to these days. What an @$$!
I bought off on the “runaway greenhouse” idea on Venus for several decades (without smoking pot) and only very recently have come to understand that the theory is beyond absurd. I explain below.
This should be revolutionary enough to win the author a Nobel Prize, right?
The first problem is that the surface of Venus receives no direct sunshine. The Venusian atmosphere is full of dense, high clouds “30–40 km thick with bases at 30–35 km altitude.“ The way a greenhouse effect works is by shortwave radiation warming the ground, and greenhouse gases impeding the return of long wave radiation to space. Since there is very little sunshine reaching below 30km on Venus, it does not warm the surface much. This is further evidenced by the fact that there is almost no difference in temperature on Venus between day and night. It is just as hot during their very long (1400 hours) nights, so the 485C temperatures can not be due to solar heating and a resultant greenhouse effect. The days on Venus are dim and the nights are pitch black.
CRASH! Right away the author discredits himself. He assumes that only direct sunlight can cause surfaces to warm. WRONG! Light is light and does not have to be direct to warm something, though the warming would be less. Remember all those Venera pics taken on the surface? Since the daytime surface of Venus is about as bright as an overcast day on Earth, those pics were taken naturally. Also, superheated gas can transmit heat to surfaces through movement and direct contact, even in darkness. There are winds constantly moving on Venus, after all.
The next problem is that the albedo of Venus is very high, due to the 100% cloud cover. At least 65% of the sunshine received by Venus is immediately reflected back into space. Even the upper atmosphere doesn’t receive a lot of sunshine. The top of Venus’ atmosphere receives 1.9 times as much solar radiation as earth, but the albedo is more than double earth’s – so the net effect is that Venus’ upper atmosphere receives a lower TSI than earth.
It’s only a problem if you ignore how totally thick Venus’ atmosphere is.
The third problem is that Venus has almost no water vapor in the atmosphere. The concentration of water vapor is about one thousand times greater on earth.
Water vapor is a much more important greenhouse gas than CO2, because it absorbs a wider spectrum of infrared light – as can be seen in the image below.
Even worse, if earth’s atmosphere had almost no water (like Venus) temperatures would be much colder – like the Arctic. The excess CO2 does not begin to compensate for the lack of H2O. Water vapour accounts for 70-95% of the greenhouse effect on earth. The whole basis of the CAGW argument is that H2O feedback will overwhelm the system, yet Venus has essentially no H2O to feed back. CAGW proponents are talking out of both sides of their mouth.
To illustrate the profound stupidity here, look at these:
Another thing to consider is how serious the greenhouse effect of Earth’s atmosphere really is. Without it, Earth’s average temperature would be about -18 degrees C, which is about 32 degrees C different from Earth’s actual average temperature (14 degrees C). Again, people who are not scientifically trained have difficulty grasping this, since they think of temperatures below “room temperture” (18 to 24 degrees C) as being cold. But in fact, it is quite warm compared to most of the universe. The cosmic microwave background (CMB) radiation, a leftover remnant of the Big Bang, is about 2.7 degrees above absolute zero, which is itself about −273 degrees C. Thus an object recieving radiation from no other source would still have a temperature of -270.45 degrees C. The Earth recieves radiation from the Sun that by itself adds about 252 degrees C to its temperature. That’s a LOT of heat! The greenhouse effect adds only about 1/8th more heat to Earth. But that is still enough to make the difference between a frigid, lifeless planet and one with oceans filled with life.
Because CO2 is lower in the atmosphere, it traps heat closer to the surface. Trapped heat causes evaporation. The H2O quickly rises and as it does, it cools. In some cases, the relative humidity of the rising H2O exceeds 100% and that results in the formation of clouds, which block and reflect sunlight. And this nullifies H2O’s greenhouse effect and it instead becomes a cooling agent, all the way down to the surface. It is common knowledge that cloudy days are cooler than clear ones. The only times the greenhouse effect of H2O is really significant is at daytime when the sky is clear, and at night when the sky is cloudy. In the latter case the clouds hold in heat that would otherwise escape when the sky is clear.
And we are dealing with a planet, Venus, which is closer to the Sun, has an atmosphere 90 times thicker than that of Earth, and has an atmosphere of mostly CO2 (that gas only forms a trace amount on Earth). There is NO need for a water vapor feedback on Venus! CO2 can do it all!
So why is Venus hot? Because it has an extremely high atmospheric pressure. The atmospheric pressure on Venus is 92X greater than earth. Temperatures in Earth’s atmosphere warm over 80C going from 20 kPa (altitude 15km) to 100 kPa (sea level.) That is why mountains are much colder than the deserts which lie at their base.
The atmospheric pressure on Venus is greater than 9,000 kPa. At those pressures, we would expect Venus to be very hot. Much, much hotter than Death Valley.
But the author does not specify how much hotter, does he? That will become important later.
Wikipedia typifies the illogical “runaway greenhouse” argument with this statement.
Without 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.
No it wouldn’t. 9000 kPa atmospheric pressure would occur on earth at an altitude many miles below sea level. No such place exists, but if it did – it would be extremely hot, like Venus. A back of the envelope estimate – temperatures on earth increase by about 80C going from 20 to 100 kPa, so at 9,000 kPa we would expect temperatures to be in the ballpark of :
20C + ln(9000/(100-20)) *80C = 400C
This is very close to what we see on Venus. The high temperatures there can be almost completely explained by atmospheric pressure – not composition. If 90% of the CO2 in Venus atmosphere was replaced by Nitrogen, it would change temperatures there by only a few tens of degrees.
Only 90%? Ah, there’s the dishonesty. The argument would have had merit if the author had said nearly 100%. This is a denialist con job, pure and simple!