The greenhouse effect is real. If there were no greenhouse gases in the atmosphere, earth would be a cold place. Compare Mars versus Venus – Mars has minimal greenhouse gas molecules in its’ atmosphere due to low atmospheric pressure, and is cold. By contrast, Venus has a lot of greenhouse gas molecules in its’ atmosphere, and is very hot. Temperature increases as greenhouse gas concentration increases. These are undisputed facts.
outgoing radiation = incoming radiation – changes in oceanic heat content
The image below from AER Research explains the radiative balance.
http://www.aer.com/scienceResearch/rc/rc.html
About 30% of the incoming shortwave radiation (SW) is reflected by clouds and from the earth’s surface. 20% is absorbed by clouds and re-emitted back into space as longwave (LW) radiation. The other 50% reaches the earth’s surface and warms us. All of that 50% eventually makes it back out into space as LW radiation, through intermediate processes of convection, conduction or radiation. As greenhouse gas concentration increases, the total number of collisions with GHG molecules increases. This makes it more difficult for LW radiation to escape. In order to maintain equilibrium, the temperature has to increase. Higher temperatures mean higher energies, which in turn increase the frequency of emission events. Thus the incoming/outgoing balance is maintained.
Click for larger image
http://www.aer.com/scienceResearch/rc/m-proj/lbl_clrt_mls.html
The important greenhouse gases are: H2O, CO2, O3, N2O, CO and CH4. The reason why the desert can get very cold at night is because of a lack of water vapor. The same is true for Antarctica. The extreme cold in Antarctica is due to high albedo and a lack of water vapor and clouds in the atmosphere, which results in almost all of the incoming radiation returning immediately to space.
An earth with no CO2 would be very cold. The first few tens of PPM produce a strong warming effect, and increases after that are incremental. It is widely agreed that a doubling of CO2 will increase atmospheric temperatures by about 1.2C, before feedbacks. So the debate is not about the greenhouse effect, it is about the feedbacks.
Suppose that the amount of reflected SW from clouds increases from 20% to 21%? That would cause a significant cooling effect. Thus the ability of GCM models to model future temperatures is largely dependent on the ability to model future clouds. Cloud modeling is acknowledged to be currently one of the weakest links in the GCMs. Given the sensitivity to clouds, it is perhaps surprising that some high profile climate scientists are willing to claim that 6C+ temperature rises are established science.
So the bottom line is that the greenhouse effect is real. Increasing CO2 will increase temperatures. If you want to make a knowledgeable argument, learn about the feedbacks. That is where the disagreement lies.
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Im not convinced that the greenhouse effect is anything but miniscule.
Temperature on the different planets are clearly dependent on the distant to the sun and pressure of a given place in the atmosphere.
For instance, if you go deep enough on Jupiter and Saturn you will find temperatures higher than on Venus surface.
If you just go down to 1 atm pressure in Venus atmosphere you will see that the temperature is just 50-60 Kelvin warmer than earth, quite predictable considdering the shorter distance to the sun.
Also, take a look at Titan (Saturns moon). Titans atmosphere is clearly NOT better isolating than Saturns atmosphere. In fact, Titan is almost as cold at 1,5 atm as Uranus!
The funny thing is, that Saturn is almost 100% pure Hydrogen and Helium, only trace amounts of Greenhouse gasses. But Titan, the cold globe, has no less than 5% Greenhouse gasses! And its not just one greenhouse gas, its Methane, Ethane and many many other substances…
No. Im not convinced at all. H2O in the form of droplets (clouds) like any other types of clouds has micro phase shift between liquid and gas. THIS is effective to back-radiate. The thing is, Droplets Backraiates ALL frequencies, not like for instance CO2 that doesnt back radiate anything. It just changes the direction of heat randomly and only for a specific frequency. The thing is: As long as there is a hole in the bucket, it will not hold anything. CO2 and the greenhouse gasses does not by long shot close the hole in the bucket. Heat with the speed of may be hold back some split seconds before – via earth or otherwise – finding a frequency that the greenhouse gasses does not stop. We are talking split seconds, and thus an inferior impact on temperatures.
Im of course not sure of this, but this makes the best sence to me.
If you put your head in the oven, and your feet in liquid nitrogen, you will on average, have a temperature of 37 degrees.
The Earth rotates, and the surface temperature changes throughout the day.
incoming radiation changes throughout the day.
Outgoing radiation changes throughout the day.
Humidity changes throughout the day.
Air pressure changes throughout the day.
Attempting to impose an equilibrium model on a steady state system is beyond simplistic, it is stupid.
A minimum equilibrium model would slice the day into 24 intervals and examine the quasi-equilibrium and examine the heat influx and efflux into heat reservoirs.
Here is a clue, the Earths surface is >70% water and under goes a phase transition on heating and cooling, as such during an energy input water turns to vapor and, during the night, it turns to a liquid.
The equations I have seen for atmospheric physics of doubling CO2 (from 280ppm) seem very simple, and the spread for no feedback is 0.5-1.5C in the published literature. The gain factor added for global modelling of the consequences is usually 3 – and this is the fabled water vapour feedback. Lindzen criticised this in the first IPCC assessment as unproven, and argued it could be zero if the water vapour condensed to cloud. Hence no runaway. Hansen’s models assume the gain factor is 3. These assumptions can be tested by observation. If we look at the tropospheric air temperature – it has risen (with some variability) by 0.5C for a 35% increase in GHG. The latest MSU data shows about 1C anomaly for 2008, and January 2009 maintaining that anomaly. So it would appear the atmosphere is warming as expected.
However, surface temperatures show cooling of .3C for 2007 and 2008.
Surface temperatures are not driven by atmospheric temperature, but by ocean heat content and its transfer to land (Compo & Sardeshmukh, ‘oceanic influences on recent continental warming’ Climate Diagnostics Centre, University of Colorado.)
So the oceans are the key, and as everyone points out, there is very little power in the atmospheric heat content to affect the ocean heat content – it can only happen by lessening the heat gradient and heat loss, but this is dominated not by CO2 but by H2O, and by cloud cover.
The key is clouds. And if we look at all the satellite derived cloud data we see a steady fall in low level reflective clouds from 1983 to 2006 and a rise from 2001 in mid and high level clouds that are probably more insulating than reflecting.
Data at NASA for surface Short Wave flux confirms the cloud thinning – with the anomaly at 4-6 watts/sq metre (average global) persisting for many years in periodic pulses from 1983-2000 (vaguely mirroring the 11-yr solar cycle) and contributing far greater energy than the (computed) CO2 radiative forcing of less than 1 Watt/sq metre (increment over the period).
Thus, the ‘global warming’ of 1980-2005 (a 25 year period), and without which there would be no peripatetic James Hansen, and probably no IPCC either, has clearly been driven by extra SW radiation reaching the earth’s surface due to cloud changes. These changes could be ‘claimed’ as AGW effects, but they are not predicted in the models – which have inadequate cloud components. As we know that ocean basins have low frequency oscillations (e.g. the PDO at 30 years) that are independent of CO2 concentration, but show correlations of solar magnetic cycles, we ought to suspect that the excess SW and cloud changes are part and parcel of the natural ocean cycles. Thus, they have amplified the ‘global warming’ signal, and now they are suppressing it.
However, my nearby Hadley Centre, having become an integral part of the IPCC system, only draws attention to the latter – the power of the cycles to now bring an intermission of global cooling (they don’t call it cycles, however because their models cannot replicate cycles – so they call it natural variability – implying randomness, which is more readily simulated) .
The surface temperature of the oceans is not the best guide to the warming period. As IPCC tell, 84% of the ‘warming’ is held in the oceans as heat content. Oceanographers tell that this heat is trapped in the upper layers down to about 700m, but most is in the first 200m. Interestingly, that ‘upper ocean heat content’ (best phrase to google for data sets) is concentrated in two major zones – the northern pacific and atlantic gyres, whereas the southern oceans tend to dissipate more (John Lyman and NOAA, and Hadley Centre (HADOBS) have maps. These two zones are very sensitive to shifts in cloud cover and these are timed by the respective PDO and its Atlantic equivalents (NAO at 10-20 years, and AMO at 60-100 years), and also interact with the Arctic Oscillation (about 70 years). Incidently, the whole of the Arctic melt-down is explained by the penetration of North Atlantic warm water and excess cloud over the polar ice (14% up between 1980-2000), and the 2008 turning of the trend was predictable once the PDO shifted to its cold phase in 2006/2007. The ice is melted from above by IR radiation from the excess cloud and below by warm North Atlantic water penetrating further north than usual – due to a weakened Beaufort Sea gyre associated with the warm phase of the PDO. With the PDO in cold phase, the ice will come back, as long as the North Atlantic doesn’t get warmer – and it seems to be at the end of its own warm phase.
As we know, the oceans stopped accumulating heat around 2002, at the same time as there was a step change in global cloud cover (measured as percentage increase). However, percentage may not be as important as a spatial shift (e.g. southerly shift of the jetstream). The jetstream is very sensitive to the solar cycle – both due to UV flux and it would seem, the magnetic cycle (though the two are related). During the Little Ice Age there is evidence the jetstream shifted south for some considerable period – as it did in 2007 and 2008 in the current solar low.
If significant cloud banks moved to uncover and expose the main gyres, they will lose heat.
These two ocean heat stores affect the planetary heat budget via teleconnections to other ocean basins – though Antarctica seems insulated and tends to go in the reverse direction to what happens in the northern hemisphere.
There is no direct evidence in the Long Wave data for CO2 build-up effects because the flux is so dominated by LW emissions from clouds (whether upward or downward).
Thus, the only direct evidence for causal drivers of the observed global warming and recent ‘pause’ relates to cloud cover and SW flux, ocean absorption of heat and the remix of ocean heat content. If CO2 contributes, that contribution cannot be greater than 20% (by comparision to the wattage from SW compared to the computed radiative forcing wattage) and as the computed CO2 signal is uncertain, I would say there is a range of 10-20%.
If we assume the world emission control programme halves current emissions by 2050 (very unlikely, I know), this will address only 5-10% of the driving force and hence, whatever other benefits might accrue, be ineffective in the stated aim of ‘avoiding climate chaos’.
Stunning. Reasic hasn’t shown up yet to tell you how wrong you are.
I thought that Mars’ atmospheric pressure was about 1% the earths. And it’s atmosphere was about 100% CO2.
If so, that would give it more CO2 in it’s atmosphere than the earth has.
How much would a drop of boiling water heat my pint of beer?
I posted earlier
Or is the difference of potential heat content of no importance?
Steven – thank you for such a full answer. I agree with you entirely that climate sensitivity is the most significant area of discussion.
“outgoing radiation = incoming radiation – changes in oceanic heat content”
Oh, OK, I saw that you made a balance at the edge of the amtosphere. But the mechanisms that I described are correct (I hope)
And what happened to the LW backradiation to the surface?
It simply warms slightly the surface
Nooo! We must obey the rules of thermodynamics, like Homer. So also the second rule, i.e. no colder matter (atmosphere) can warm a warmer matter (earth).
Correct: The LW backradiation is lessening the net radiation of the surface
Hmm, I don’t understand how CO2 radiation is going to heat the oceans considering the IR radiation is absorbed within the first 1-2 mm. Add to that the weight of the atmosphere of only 0.389% of the oceans and that only 380ppm of those 0.389% are CO2. I don’t see how that should be possible in any shorter therm period or at all…
OT – Sorry Guys
Federal US Budget calls for Carbon Cap and Trade as a part of Obama’s cut the deficit in half pledge by end of first term.
“Another official said the budget included hundreds of billions of dollars in revenues, starting in 2012 and going over many years, from a greenhouse gas emissions trading system, one of Obama’s key proposals to fight global warming.”
See my site for more Info and read my Dangers of Implementing Cap and Trade in a Recession post
Tell me where I am wrong…
Energy arrives at the earth in units (a rose by all your other names is confusing)
This energy (neither created nor destroyed, but changing forms) hangs around for a while, then makes it’s exit into the vastness of space.
If this unit of energy (and all its companions) hangs around for a longer time, Earth gets warmer. If it exits sooner Earth gets cooler.
This is slightly complicated by the fact that the Earth generates some of its own energy. (for those who care, measured in milliwatts per meter squared) And, the number of units, in coming, changes for various (and in some cases unknown and unmeasured) reasons.
Then calculating global warming/cooling is a simple calculation in probability: What is the probability a unit of energy will hang around for a while. High probability=warming, low probability=cooling.
The unit of energy strikes a molecule and is reflected or absorbed (and changes form). It is retained or changes form again as it is sent on its merry way. The unit of energy then strikes another molecule and is reflected or absorbed. It is retained or changes form again as it is sent on its merry way, again. Etc.
How hard can this be? A little physics, a little chemistry, a little probability and a huge computer…
A good point often missed. Isn’t it also true that each time the LW is absorbed and emitted the wave length increases, indeed isn’t this true of all electromagnetic radiation?
Steve
I take strong exception to your statement, “There is no dispute about this in the scientific community” when, from what I see, that there is some very strong dispute about this whole subject of AGW. If you are not able to acknowledge this plain fact, why should we give credence to anything else you say?
Also, Venus is hot because it is so close to the sun. Stand near to the fireplace and you’ll understand.
Yes, the greenhouse effect of CO2 is real. And, CO2 seems to be rising along with temperature. That’s why Anthropogenic Global Warming is a “plausible” hypothesis — and worth studying.
Thing is, AGW via greenhouse effects as a significant factor in Earth’s climate is an “unproven” hypothesis. Moreover, even if AGW takes place, genuinely catastrophic AGW seems “implausible” as one digs deeper into all the aspects (assuming humankind can adapt to a few feet of sea level rise and substantially improved global food production).
Good questions coming in.
Remember that,heat is not trapped. If it were trapped, the earth would be incredibly hot. The energy remains in balance, as Homer clearly stated.
The article does mention convection, and re-radiation is equally likely in any direction (including downwards.) That is why a cloudy nights are warmer.
Heat flow is driven by temperature differences. If the atmosphere is warmer over the ocean, then less heat flows out of the ocean into the atmosphere, and the ocean warms up. And vice-versa.
Steven Goddard:
“Temperatures are very sensitive to H2O levels, particularly at night. Which is why deserts get cold at night. H2O is the most important greenhouse gas.”
This is a myth. It is true only for high-altitude deserts. The night-time temperatures in Phoenix in the summer are WARMER than they are in the South at the same latitude. For example, the average minimum July temp. in Phoenix is 27.2 C; whereas in Birmingham, AB and Atlanta, GA the average July minimum is 20.8 (30-year averages).
BTW, please explain to me why it gets so much hotter in deserts than in humid areas at the same elevation and latitude, if the greenhouse effect works as shown here. As noted, water is the most important greenhouse gas, and there is about 3-4 times as much of it in humid areas than in deserts. Also, explain why it almost never gets over 33 C in the humid tropics (where water vapor levels are always 4 times those in deserts); whereas 50 C is very common in deserts. Negative feedback by water is a fair explanation, IMHO.
Steven Goddard (23:35:29) :
That’s one of the reasons. One other is that dry soil is a decent insulator so the heat flux to the surface is low. Another is that in humid areas, the heat released by dew formation significantly slows down cooling. Even when dew forms in the desert, there’s so litte water vapor to work with it cooling isn’t impeded as much as in humid areas.
There are some areas in Eastern Oregon where surrounding basalts acted like the urban heat island from hell. It did not get cold at night! With daytime temps over 100F (40C), it was not the most comfortable bicycling. Soaking our jerseys in any water we could find helped a lot though.
BTW, I’ve written a “State of the Climate” report that starts with a very similar graphic as Steven uses at the top of this article, see http://wermenh.com/climate/climate2009.pdf
I’ll make it the link from my name.
All the greenhouse gas molecules can do is slow down (a little) the rate at which the energy leaves the atmosphere. They cannot in any way ADD heat; only the Sun can do that. One problem with all the nice little radiation cartoons is that they ignore convection, which counterbalances the slow-down caused by the radiation. It’s much more complicated than shown by the radiation cartoons.
And I’ll bet that water completely overwhelms any small effects by CO2, probably making them negligible.
Ric,
I did a canoe trip down the Green River in Utah about 25 years ago in July. It was too hot to sleep when you went to bed, and too cold to sleep when you woke up!
Here is an interesting statement made by William Happer Cyrus Fogg Brackett Professor of Physics Princeton University to U.S. Senate Environment and Public Works Committee Senator Barbara Boxer, Chair on 25 February 2009:
http://nzclimatescience.net/images/PDFs/happer.pdf
At least some parts of the US Congress would appear to be prepared to listen to well reasoned and balanced arguments about the true state of Climate Change research and the role played by CO2.
Maybe this is part of an overall slow moving process resulting from the “braking” of global warming since 1998. Who knows? Time will show.
BTW, excellent post Steve. The strawman argument that all alarmist use is that we (skeptics/deniers/flat-earthers) do not believe adding CO2 increases temperature when the ENTIRE argument is in the feedbacks.
Allen63 (05:20:14) :
Yes, the greenhouse effect of CO2 is real. And, CO2 seems to be rising along with temperature. That’s why Anthropogenic Global Warming is a “plausible” hypothesis — and worth studying.
————–
During the 60’s and 70’s, temperatures fell, even though CO2 was rising.
Over the last decade, temperatures fell, even though CO2 was rising.
Note the upwards curve from renowned skeptic Dr. Lindzen in the quadrupling graph above. Skeptical scientists do believe that increasing CO2 increases temperature. Dr. Spencer says the same thing.
http://miskolczi.webs.com/
As I understand F. Miskolczi’s theory, he discovered a negative feedback term when the differential equations for radiation transport were solved with the correct finite thickness for the atmosphere. This eliminated a 20° discontinuity between the surface an the bottom of the atmosphere that was present in the old incorrect solution with the infinitely thick atmosphere. This shows the new solutions are correct.
The earth has a infinite supply of green house gases in the form of water in the oceans. The earth underwent a runaway greenhouse effect eons ago due to all this water and the temperature went up until the negative term became important and an equilibrium was reached. The earth has been existing at a balance point ever since.
According to Miskolczi, as we add CO2 to the atmosphere, the balance is maintained by a little water raining out. The optical density of the atmosphere remains constant. The amount of water in the atmosphere has decreased over the last fifty years as CO2 has risen.
http://www.climateaudit.org/phpBB3/viewtopic.php?f=4&t=556
The climate models have a built in positive feedback for CO2 warming because the models assume constant relative humidity. This is wrong by the data (and the theory.) Most important is that a runaway greenhouse effect is impossible.