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.
David Ermer,
Like I said, this is not intended to be a qualitative article. The analogy is just to point out that more stoplights increase the difficulty of getting from point A to point B. The relationship with CO2 is of course not linear as you pointed out – a doubling of CO2 only impacts by 0.5% in temperature.
How can anyone state that CO2 is a “greenhouse” gas when the atmosphere it is in NOT a greenhouse?
http://www.globalwarmingskeptics.info/
The link in the comment was a mistake.It was supposed to be in the website box.Not related to my question.
gary gulrud says:
The factor of 4 difference comes from the factor of 4 difference between the total surface area of the earth, which is 4*pi*r^2 and the earth’s cross-section as viewed from the sun (which is a circle of area pi*r^2). [Another way of thinking about this is that the 1360 W/m^2 is the intensity you would have if the sun were directly overhead; however, at any given time, half of the earth isn’t facing the sun at all and the other half all has the sun at some non-normal angle (except for the one point where it is directly overhead). So, averaged over the entire surface of the earth (or top of the atmosphere, if you want to get technical), the amount is 341 W/m^2.]
jeepndesert,
Thanks for the listing as a Gore climate conspirator. I’m already listed as an oil company shill trying to destroy the climate. I’m just trying to get at the facts, whatever they may be. Maybe this year will be the hottest year ever, as Hansen predicted?
Speaking of which my UAH forecast for February is down from January at 0.24-0.26. I missed by 0.01 last month.
You inspired me to quickly write a great new blog post in response to the inconvenient truths you left out of your article.
http://newworldliberty.wordpress.com/2009/02/26/global-warming-is-a-hoax-quick-and-dirty/
Holy cow. Well, at least the issues have been laid on the table, and the points-in-dispute have been made apparent. I guess a mulligan is in order.
Steve Goddard:
Not a lot, comparatively speaking, but still a substantial amount.
Tom says:
No it doesn’t. If the positive feedback is sufficiently strong that the first order response is greater than the original effect (e.g., if the temperature response from feedbacks is greater than the bare response), then you have a diverging series and you are correct. However, if the positive feedback is weaker than this, then what you get is amplification, for example: 1 + 1/2 + 1/4 + 1/8 + 1/16, an infinite series that converges to 2.
Your statement is erroneous for the reasons that I noted above. In fact, the evidence from past historical events such as the eruption of Mt Pinatubo and the ice age – interglacial oscillations is the main line of evidence leading to estimates of what the feedbacks and resulting climate sensitivity is. And, most scientists have concluded that the sensitivity is 2-4.5 C for a doubling of CO2, which corresponds to about a doubling to a quadrupling of the “bare” response by net positive feedbacks.
It is not perjury if he sincerely believes this, which I think he does. However, that doesn’t mean that he is right.
Again, you are confusing the issues of positive feedback, true runaway, and also the possibility of tipping points. These are three distinguishable things. I think that most climate scientists would say that a net positive feedbacks is very likely, tipping points are quite possible (given the historical record) but we don’t know where they are, and an actual runaway is unlikely (although Hansen would claim otherwise…if we really don’t restrain ourselves at all in burning fossil fuels).
A positive feedback…that´s alchemy. We need some to overcome financial crisis. Kind of Keynesian meteorology!!
Steven,
I appreciate the attempt to find some common ground on what we agree on and where uncertainties remain. I agree that the radiative forcing of CO2 is one of the areas where we can be fairly confident in our projections, but that overall climate sensitivity (taking into account various feedbacks) is where the major debate lies.
Unfortunately, it seems by the comments that many folks have reached a point where any suggestion of the role of CO2 in warming the planet is dismissed out of hand. A bit of common ground would go a long way toward having a more constructive dialogue between both sides of the climate debate (which, as an aside, is why I enjoy Lucia’s place; no need over there to waste time arguing with people who conflate CO2 flux with CO2 stocks, for example).
Positive feedback: the perpetual movement
Joel Shore says: (albeit a quote from someone else):
“The surface of the Earth is warmer than it would be in the absence of an atmosphere because it receives energy from two sources: the Sun and the atmosphere.”
I suppose that should be quantified (at least as I understand it)
The atmosphere (and the oceans) cool the surface while the sun is shining upon it, and prevent heat from leaving as quickly it might otherwise when the sun is not shining on it, thereby maintaining a mean temperature that we calculate is higher than might otherwise be the case.
In my interpretation, that puts the bulk of the mean difference as happening on dark surfaces of the earth when no SW radiation is incoming. Certainly, it seems plausible that LW radiative heating may have a stronger effect when there is no higher energy source of radiation entering the system., but it seems a stretch to attribute the warming that is claimed to it.
As the oceans have a huge thermal inertia compared to the atmosphere, and the surface temperatures are definitely not as hot as they would be without an atmosphere, I wonder why the atmosphere is the prime candidate for “carrying” the heat through the nighttime hours. Surely the medium that loses least energy over a certain period when an incoming source is terminated would be a more reasonable “culprit” for maintaining an average temperature in a system.
I am no expert, I am just applying my own twisted logic to the argument. I’m perfectly happy to be educated by anyone who knows better, even if it involves an egg/face incident.
Without the sun to feed it, there is no feedback! Like pretty much all Law of nature, we should be dealing with an exponential relationship and nit just some “constant” number to represent the feedback.
Stevo says:
Sort of…but a little clarification is in order. If the hotspot in the tropical atmosphere is really absent (which I think is doubtful but the observational data is inconclusive at this point) then the most direct consequence of this is that the lapse rate feedback in the models, which is a NEGATIVE feedback that counters part of the positive water vapor feedback, is absent. So, the most direct consequence would be to imply that there should be more warming than the models predict. [The rough logic for this is that the place in the atmosphere that has to heat up a certain amount in order to put the earth back in radiative equilibrium is the upper troposphere. So, if the tropical upper troposphere is not heating more than the surface (as the models now predict), then the surface would have to heat up more in order to get the tropical troposphere heated up the necessary amount.]
Now, one can argue that if the models are not getting these convective aspects correct, they are likely wrong on the water vapor feedback too. However, since we have some independent observational verification that the upper troposphere is moistening approximately as expected (from Brian Soden’s work and also Dessler’s work), this seems unlikely.
Princeton Physicist Tells Congress Earth in ‘CO2 Famine’ — Increase ‘Will Be Good for Mankind’
http://www.businessandmedia.org/articles/2009/20090225213407.aspx
Stevo (11:09:20) :
As good an explanation as I’ve seen.
“The factor of 4 difference comes from the factor of 4 difference between the total surface area of the earth, which is 4*pi*r^2 and the earth’s cross-section as viewed from the sun (which is a circle of area pi*r^2). ”
Thank you.
It may well be a good explanation of the AGW theory and clearly greater minds than mine will debate and argue for a long time to come.
However the article at this stage smacks of the desperation of the AGW’s.
Those in the know do not dismiss the basic theory…it is the outcome that is the sticking point.
As Prof Bob Carter said in his presenatation in Sept 2007…they put in the positives of their argument but not the negatives.
There has been no warming for around 10 years and the Aqua satellite did not find the hot spots in the upper atmosphere it should have done.
The Polar Ice Caps are returning and the changes we are experiencing from the change in the sun cycle are clearly at odds with the dire warnings of the AGW theory.
In fact the BBC even published an article from the Guardian regarding a recent admission by the Hadley centre that some of the more catastrophic outcomes of the increased CO2 levels are somewhat wide of the mark.
Having no scientific training I just use commonsense.
References to James Hansen being “correct” are in fact part of the admission that although his theory is correct…his wild predictions on the eventual outcome are not.
Good luch all of you who are qualified to debate this…we await the outcome with interest.
What in the world are the units on the x-axis of the second figure (1st plot with estimated temperature vs. something?)?
Huge pet peeve… not labeling axes!!
Paddy (11:52:11) :
Of course the “Earth was just fine” millions of years ago when CO2 levels were much higher. It was just fine when temperatures were higher or lower, just fine when sea levels were higher or lower, and so on. The changes from one state to another, however, have gone along with the evolution of life on the planet. In the case of rapid changes (which might be measured on the scale of tens or hundreds of thousands of years), some such changes are associated with mass extinction events. We’re currently considering the impact of changes on a century scale or less. The concerns are not for whether the planet will surivive (it will) but whether we can support our current population and its geographical distribution, along with out current biodiversity.
Hasit been, 11:07:20
“Wide Temperature Range
Temperatures in arid areas may get as high as 55 degrees C during the day and as low as 10 degrees C during the night. The drop in temperature at night occurs rapidly and will chill a person who lacks warm clothing and is unable to move about. The cool evenings and nights are the best times to work or travel. If your plan is to rest at night, you will find a wool sweater, long underwear, and a wool stocking cap extremely helpful. “
These types of accounts are what cause the MYTH of the frigid desert night and super hot days. This ONLY occurs at high elevations (and high latitude). It does NOT occur at low altitude deserts below 45 N/S latitude. In fact, It has nothing at all to do with deserts; it occurs at high elevations EVERYWHERE, not just in deserts. Look, for example, at Alamosa, CO, which is at about 2300 m elevation. It is not considered a desert, because it gets more than 5 inches of precipitation per year (mainly snow there). But a typical July day will vary from 27.8 C during the day to 8.8 C at night, for a diurnal variation of 19 C. Here you do need a coat at night! But it is no worse in any high altitude desert. For example, look at Tonopah, NV, which is at 1653 m elevation (even somewhat lower than Alamosa). Here the average high in July is 32.8 C and the average low is 13.6 C, for about the same diurnal variation. Now look at a typical low-elevation desert, like Daggett, CA, 588 m elevation. Here the variation is from 39.9 to 23.3 C, for a diurnal variation of 16.6 C. (The average relative humidities for these locations are 56 (Alamosa), 26 (Tonopah), 24 (Daggett)).
Also note that the LOW temperature of 23.3 C in Daggett is still higher than the average low temperature for Atlanta (20.8). You do not have to dress warmly for the night-time in July in either Atlanta or Daggett.
Data at http://rredc.nrel.gov/solar/old_data/nsrdb/redbook/sum2/state.html
OT: Bloomberg story: “Obama Plan Has $79 Billion From Cap-and-Trade in 2010”
http://www.bloomberg.com/apps/news?pid=20601087&sid=akMqKTP2B1wo&refer=home
Sample quote:
“President Barack Obama’s budget plan assumes $78.7 billion in revenue in 2012 from the sale of greenhouse-gas emission permits to polluters, putting pressure on Congress to pass legislation by early next year.
“A “cap-and-trade” program would generate a total of $645.7 billion by 2019, according to the budget blueprint Obama sent to Congress today. Initial funds would be used to invest in “clean” energy, help finance Obama’s tax credit for workers as well as offset higher energy costs for low- and middle-income people and clean up costs for small businesses.
“The budget calls for the Environmental Protection Agency to get $19 million to begin setting up an inventory of greenhouse- gas emissions”
Joel Shore, 12:44:28
“I think that most climate scientists would say that a net positive feedbacks is very likely, tipping points are quite possible (given the historical record) but we don’t know where they are, and an actual runaway is unlikely (although Hansen would claim otherwise…if we really don’t restrain ourselves at all in burning fossil fuels).”
If you believe this, I have a bridge to nowhere to sell you…. 🙂
Seriously, I don’t think a significant positive water vapor feedback is possible for the following reasons. Go ahead and assume that a doubling of CO2 causes a 1.2 C rise in temperature. It is trivial to show with the Classius-Clapeyron equation that this increase in temperature can cause, at most, an 8% increase in evaporation of water. Like CO2, the relationship between concentration and radiation is logarithmic. MODTRAN shows this, if you play with the water vapor concentration and leave everything else constant. According to MODTRAN a doubling of water vapor would increase radiation by about 15 w m-2 (first doubling). Thus, an increase of 8% water vapor would amount to only (0.08)(15) = 1.2 wm-2. Negligible.
Dammit. The above should read: “Like CO2, the relationship between concentration and radiation FOR WATER VAPOR is logarithmic.”