For those who don't believe in global warming

[Stella]

Well now that the dems have congress, I expect global warming to reverse, poverty to cease, cancer to be cured, terrorism ended, and New Orleans rebuilt within 6 months.

[DCJenn]

Don't forget balance the budget.

We are Dems, hear us roar.

(um, in all honesty I seriously hope what happens is that everyone untwists their panties and realizes that if they don't work together, once again nothing will be done. I know that part of the reason why things didn't get accomplished this yhear is that Pelosi and Dean had the automatic response of "if they want it it must be a bad thing" which is utter insanity. I'm fairly certain the Republicans as a group aren't the Demons that they have been made out to be- and lest anyone think that these Dems are the tree-hugging, free programs to all Dems of the 1970s- this groups is as conservative as many of the Republicans.)

[Rapunzel]

I adore science. And, I would like to point out that correlation does not equal causation.

Climate change happens - and has happened, well, since the earth had a climate. Humans do affect the climate in certain ways to some extent (both positively and negatively according to what is best for humanity - like increased food production).

Sometimes the hysteria over perceived problems gets a little crazy, though. I'm just waiting for the day that some Greenpeace guy starts claiming that jackhammers cause increased seismic activity over the entire Earth, for example.

Here's an excellent website that removes the silly hype that is popularized today and discusses the nitty-gritty science of climate change:

http://www.junkscience.com/Greenhouse/

Greenhouse, global warming - and some facts
JunkScience.com
April 21, 2006


Given the number of JunkScience.com readers expressing some confusion over the "greenhouse effect," carbon dioxide, global warming and climate change, we thought it might be a good idea to pull together a page of questions-and-answers, complete with a few nice little graphics explaining the facts.

We thought that since there is long-standing, intense public interest in these topics and that vast sums of public and private monies are being thrown at the much-dreaded "problem" of "global warming," there should be a wealth of quality explanations and graphics to which we can point readers to alleviate their confusion.

That was about the time that our quick project and quiet weekend went awry very quickly.

Who would have thought so many "issue" sites, environment sites and, yes, government sites, could be hosting so much utter garbage on a topic subject to such intense scrutiny? Who could have imagined having to spend several hours wading through searches to find a few simple graphics correctly expressing the greenhouse effect? Who knew that so many blowhards are out there pontificating from complete ignorance?

Some of the bad descriptions appear to be poor efforts at simplifying the material to suit grade school course work and the like, but that does not make them any more acceptable. Obviously a slight rethink of this project was necessary. We will now try to deliver an extremely simplified version of how this greenhouse thing actually works and some indication of what might be expected from what is known about the Earth and what has been measured, rather than simply guessed about.

Basic misconceptions that must be addressed include:
Does the Earth's atmosphere primarily behave like an actual greenhouse?
No. The term "greenhouse effect" is unfortunate since it often results in a totally false impression of the activity of so-called "greenhouse gases." An actual greenhouse works as a physical barrier to convection (the transfer of heat by currents in a fluid) while the atmosphere facilitates convection. So-called "greenhouse gases" in the Earth's atmosphere do not act as a barrier to convection so the impression of actual greenhouse-like activity in the Earth's atmosphere is wrong.

For an expanded description of physical greenhouses see Sue Ann Bowling's ASF piece here.

Supplemental, April 25: A couple of people have written challenging whether physical greenhouses function as convection barriers since they do radiate and so does the atmosphere - apparently we need to expand on this point. To begin with, a physical greenhouse is simply a contained subset of the atmosphere - it is not bounded by the near-vacuum of space as is the planet's atmosphere and so has rather different properties. The proof that convection containment is critical to the function of physical greenhouses is that it is possible to create structures with similar radiative properties, one which allows convective activity between the structure and unconstrained atmosphere and one which does not. Only the structure constraining internal-external convection will function as an effective greenhouse. Greenhouse gases categorically do not inhibit convective activity and so are not like a physical greenhouse.

Forgetting about the unfortunate-but-commonly-used terminology for a moment, is the so-called 'greenhouse effect' bad?
Only if you think undesirable a habitable planet with relatively stable temperature. Our moon, lacking greenhouse effect, makes a kind of comparison even though lack of atmosphere makes it uninhabitable regardless of temperature. The moon's mean surface temperature by day is 107 °C (225 °F) and by night drops to -153 °C (-243 °F). The Lunar temperature increases about 260 °C from just before dawn to Lunar noon. So, if you fancy such a temperature range then a greenhouse effect-free world is for you, otherwise you might want to be pleased we have it here on Earth.

How much does the so-called 'greenhouse effect' warm the Earth?
It's estimated that the Earth's surface would be about -18 °C (0 °F, 255 K) with atmosphere and clouds but without the greenhouse effect and that the (we'll call it "natural") greenhouse effect raises the Earth's temperature by ~33 °C (59 °F). Devoid of atmosphere it would actually be a less cold -1 °C (272 K) because the first calculation strangely includes 31% reflection of solar radiation by clouds (which could obviously not occur without an atmosphere) while clouds actually add significantly to the greenhouse effect - for simplicity, just stick with ~33 °C.

[Edited for clarity, April 24] Theoretically, if the planet's surface cooled by radiation alone, then the greenhouse-induced surface temperature would be much warmer, about 350 K (77 °C), but atmospheric motion (convective towers carrying latent and sensible heat upwards and large scale circulation carrying it both upwards and polewards) significantly increase the "escape" of energy to space, leaving Earth's surface more than 60 °C cooler than a static atmosphere would do.

So, despite there being far more greenhouse gas in the atmosphere than required to achieve the current greenhouse effect, and that has been so since before humans discovered fire, evapo-transpiration and thermals transport heat higher in the atmosphere where radiation to space is increased. This is why Earth remains about 15 °C rather than about 77 °C.

Wait a minute! Those aren't the numbers I learned!
Ah! Someone who remembers their science classes eh? Well, you got us. Reference works frequently list the planet's mean surface temperature as 16 °C (61 °F); sometimes 15 °C (59 °F) is mentioned and yes, these are about the expected temperatures by calculation -- in the 1960s and 1970s numbers as high as 65 °F (18 °C) were popular but we haven't seen those for some time. Here we run into a little bit of a problem, however -- taking the Earth's temperature is no trivial task. In fact, even defining precisely what we mean by the absolute surface air temperature is challenging. Current global temperature anomalies (the amount of warming or cooling reported) are estimated against an expected average of 14 °C (57 °F) -- the guess-timated mean temperature over the period 1961-1990.

Are greenhouse gases like a blanket around the Earth?
No, for the same reason that they don't behave like an actual greenhouse, they simply do not behave as a barrier to convective activity and so aren't "like a blanket."

Do greenhouse gases trap the sun's radiation/'heat'?
Not to any great extent. The Sun, being much hotter than Earth, emits high energy, shortwave radiation while Earth, in response, emits longwave radiation. The cooler the portion of the Earth or atmosphere, the lower energy intensity, longer wave radiation is emitted -- that old white hot, yellow hot, red hot thing. Greenhouse gases are generally transparent to incoming solar radiation -- they let most solar radiation through -- and opaque to Earth's radiation -- they absorb and transfer the Earth's infrared radiation by a variety of means. That said, oxygen and ozone do absorb incoming Ultraviolet (UV) radiation (<0.3µm) and water, ozone, oxygen and, to a tiny extent, carbon dioxide also absorb a small amount of incoming shortwave below the 3 micron (µm) wavelength range (see graphic) and it is mostly the UV absorption by ozone that causes warming in the stratosphere above the tropopause. The tropopause is the boundary between the troposphere (which is based at the earth's surface and has temperature that decreases with height, extending about 10-50Km or 6-30 miles above the surface) and the stratosphere (which is a stable region of very low levels of vertical mixing above the troposphere).

A representation of relative emission wavelengths can be seen on the following graphic.

Greenhouse gases, therefore, do not "trap heat," but could be fairly described as delaying the energy transfer from Earth to space. "Trapping heat" implies that the energy is stuck in the system forever -- this is a false notion. Greenhouse gases do not emit energy in the same bandwidth that they absorb energy, and thus emissions from carbon dioxide are not absorbed by carbon dioxide. While energy may be delayed on its inevitable journey back to space, it will eventually be emitted regardless of the number of intervening stages.

Do greenhouse gases 'reradiate' the infrared radiation they absorb?
This is an unfortunate expression that is all too common. Absorbed radiation is transformed to either kinetic or potential energy and, as such, no longer exists in its original form -- hence, it cannot be "reradiated." When molecules absorb infrared radiation they are said to become excited ("hot"). Such molecules can release energy usually in one of three ways: by chemical reaction (uncommon, since greenhouse gases are pretty stable and non-reactive); quenching (transferring energy to cooler molecules, increasing their temperature) and; emission (usually at lower energy [longer wavelength] radiation than the energy previously absorbed). Once more, since the absorbed energy has been transformed it cannot be said to be "reradiated".

Is 'greenhouse' the same as 'global warming'?
Absolutely not. We'll look at both terms below.

What about 'climate change' then?
That's a different thing altogether. Change is what the climate is always doing and is the result of our planet's orbital eccentricities, axial wobble, solar brightness variation, cosmic ray flux, etc.. There are also plausible terrestrial drivers of climate change too, including super volcanic events and tectonic movement, but these are not in the realm of anthropogenic (manmade) effects and so we won't looking at them here.

The global mean temperature over which there has been so much obsession is only one part of climate -- for example, how wet or dry the climate happens to be is probably of far greater significance than a simple mean temperature -- in fact, it's not even clear that a global mean temperature is a particularly useful metric. However, it is the cause of great angst at present so it will remain the focus of this document for that reason alone.

Graphics for a simple understanding of the greenhouse effect
This first graphic meets the criteria of being simple, doesn't say things like "reradiated" (as so many do), specifically includes water vapor and clouds as both absorbers and emitters (remarkably few greenhouse graphics do so) and is reasonably proportionate.

Big note here -- we were unable to find useful graphics adequately expressing convection, which, as we highlighted above, keeps the planet more than 60 °C cooler than would otherwise be the case.

The next graphic provides an indication of the infrared component of the planetary radiation budget. Note that these are expressed as percentages and that the 100% incoming and outgoing solar energy balance is not the whole story -- there is additional energy transfer in progress between the atmosphere and surface, and surface and atmosphere. This is the natural greenhouse effect that makes life as we know it possible on Earth. (Don't worry if you don't quite follow the numbers, we'll provide a "map" view below.)

The preceding view is very pretty and contains lots of numbers but we can perhaps get a better look at what is going on from a different representation. The following is from Earth’s Annual Global Mean Energy Budget (Kiehl and Trenberth, 1997). This is expressed in Watts per square meter (Wm-2) and tells the same story of the incoming 342 Wm-2 = outgoing (235 + 107 Wm-2). Note that there is relatively little direct reflection and radiation from surface to space but significant exchange via the atmosphere. Note further that the surface receives almost twice the energy from the atmosphere as it does directly from the sun. The exchange between surface, atmosphere and surface is what is meant by greenhouse effect. (Those not enjoying lots of numbers or missing primary colors might prefer viewing this simplified Earth energy budget)

It might also help novices to conceive of the atmosphere and the natural greenhouse effect as a kind of a metaphorical energy flow control valve. There's a lot of energy bouncing around, but the amount of energy entering the system and the amount leaving is fairly tightly constrained. The atmosphere is acting as a kind of check valve, slowing the loss of energy to space but the net incoming (324 + 168 Wm-2) = net outgoing (390 + 78 + 24 Wm-2).

Okay, if that's greenhouse, what is 'global warming'?
While greenhouse is the "what," "global warming" really refers to the "how much." Populist overuse and abuse has largely rendered "global warming" meaningless -- what is really meant is "enhanced greenhouse" -- yes, another term but don't worry, we'll explain this one easily and quickly. Since Arrhenius began speculating a century ago about low CO2 levels and ice ages the hypothesis of temperature relation to atmospheric carbon dioxide has drifted in and out of scientific focus. At present it is the focus of a great deal of attention. "Enhanced greenhouse" means the additional delay in energy loss to space induced by the fraction of carbon dioxide and other greenhouse gases released by humans before those gases are removed from the atmosphere by breakdown and/or biological activity.

So, greenhouse is all about carbon dioxide, right?
Wrong. The most important players on the greenhouse stage are water vapor and clouds. Carbon dioxide has been increased to about 0.038% of the atmosphere (possibly from about 0.028% pre-Industrial Revolution) while water in its various forms ranges from 0% to 4% of the atmosphere and its properties vary by what form it is in and even at what altitude it is found in the atmosphere. In simple terms, however, the bulk of Earth's greenhouse effect is due to water vapor by virtue of its abundance. Water accounts for about 90% of the Earth's greenhouse effect -- perhaps 70% is due to water vapor and about 20% due to clouds (mostly water droplets), some estimates put water as high as 95% of Earth's total greenhouse effect. The remaining portion comes from carbon dioxide, nitrous oxide, methane, ozone and miscellaneous other "minor greenhouse gases." As an example of the relative importance of water it should be noted that changes in the relative humidity on the order of 1.3-4% are equivalent to the effect of doubling CO2.

The adjacent radiation absorption window graphic gives an idea of which molecules absorb various wavelengths. Where the shaded portions completely span between 2 lines it indicates that particular wavelength is fully absorbed and the "window" is saturated (or said to be "closed"). Rather obviously, once a window is saturated adding more gases with the same properties will do nothing. This point seems to cause confusion for some people so perhaps consider multiple shades on a window with each shade blocking half the light coming through - pull one shade and you reduce the light source by half, pull another so you block half the light coming through the first shade, etc.. The effect of each shade diminishes as you keep adding more and eventually you get no additional effect - you have saturated or blocked the radiation window and it makes no difference if you double or quadruple the number of shades again.

Well, I heard that carbon dioxide is bad -- it's pollution, isn't it?
There seem to be a few things that your informant forgot to tell you -- like carbon dioxide being an essential trace gas that underpins the bulk of the global food web. Estimates vary, but somewhere around 15% seems to be the common number cited for the increase in global food crop yields due to aerial fertilization with increased carbon dioxide since 1950. This increase has both helped avoid a Malthusian disaster and preserved or returned enormous tracts of marginal land as wildlife habitat that would otherwise have had to be put under the plow in an attempt to feed the growing global population. Commercial growers deliberately generate CO2 and increase its levels in agricultural greenhouses to between 700ppmv and 1,000ppmv to increase productivity and improve the water efficiency of food crops far beyond those in the somewhat carbon-starved open atmosphere. CO2 feeds the forests, grows more usable lumber in timber lots meaning there is less pressure to cut old growth or push into "natural" wildlife habitat, makes plants more water efficient helping to beat back the encroaching deserts in Africa and Asia and generally increases bio-productivity. If it's "pollution," then it's pollution the natural world exploits extremely well and to great profit. Doesn't sound too bad to us.

But we're responsible for all the carbon dioxide greenhouse effect?
Gracious no! Humans can only claim responsibility, if that's the word, for abut 3.4% of carbon dioxide emitted to the atmosphere annually, the rest of it is all natural (you can see the IPCC representation of the natural carbon cycle and human perturbation here or a simple schematic from Woods Hole here). Half our estimated emissions fail to accumulate in the atmosphere," "disappearing" into sinks as yet undetermined. Humans' total accumulated carbon contribution could account for perhaps 25% of the total non-water greenhouse gases (that is, accounting for all the increase since the Industrial Revolution regardless of source and irrespective of whether warming from any cause might result in an increase in natural emission to atmosphere -- we're simply claiming the lot as anthropogenic or human-caused here).

Clarification June 4: the mention of 25% of total non-water greenhouse effect above and the following mention of 2.5% of total greenhouse effect has confused a few readers, leading to some e-mails suspecting one or the other to be a typographical error. The figures are correct. Recall that water vapor accounts for about 70% and clouds (mostly water droplets) accounts for another 20%, thus water in it's various forms is 90% of the greenhouse effect, leaving 10% for non-water greenhouse effect. Of this remaining 10%, mainly atmospheric carbon, humans might be responsible for 25% of the total accumulated atmospheric carbon, thus 0.25 x 0.1 = 0.025 x 100 = 2.5% of the total greenhouse effect.

Ah, we've added 2.5% to the total greenhouse effect then?
Not exactly, if it were such a simple accumulation, we could easily determine exactly how much Earth would warm from a doubling of atmospheric CO2 (not much) and certainly that would be an improvement on the silly figures bandied about. Theoretically, in a dry atmosphere, carbon dioxide could absorb about three times more energy than it actually does, as could clouds in the absence of all other greenhouse gases -- look at it as there already being "competition" for available suitable longwave radiation (energy these gases can absorb), if you like. Readers should be aware that the temperature effect of atmospheric carbon dioxide is logarithmic (that means there is a diminishing response as you keep adding more, like the additional window shade example, above). If we consider the warming effect of the pre-Industrial Revolution atmospheric carbon dioxide (about 280 parts per million by volume or ppmv) as 1, then the first half of that heating was delivered by about 20ppmv (0.002% of atmosphere) while the second half required an additional 260ppmv (0.026%). To double the pre-Industrial Revolution warming from CO2 alone would require about 90,000ppmv (9%) but we'd never see it - CO2 becomes toxic at around 6,000ppmv (0.6%, although humans have absolutely no prospect of achieving such concentrations).

Well, how much does carbon dioxide heat the Earth?
Oh my, we were afraid you were going to ask that. Because so many of the atmospheric processes are still being sorted out and quantified this is a non-trivial task. But alright, here goes.

What we can do is plot some of the more common estimates -- note that these are something of a curve-fitting exercise on our part because we don't have the full papers and workings at hand. Stay with us while we run through a couple of rough sketch graphs, following which we'll try a different approach to see if we can't narrow the possibilities.

We'll offer three of the more commonly used and/or discussed estimates for the amount of cooling Earth would experience for a hypothetical zero-CO2, cloud-free atmosphere; Lindzen (5.3 °C clear sky, 3.53 °C with 40% cloud), along with Charnock & Shine (12 °C clear sky), C&S are the big number guys in the estimation game (both from Physics Today, 1995) and Kondratjew & Moskalenko (7.2 °C, commonly cited but we are not sure why, perhaps because Houghton used their estimate in his book, 'The Global Climate', 1984) - here these estimates are simply scripted up to produce the following graphs and the numbers are imprecise, merely adequate to give everyone a reasonable look at how carbon dioxide fits into the picture. Note also that there is still dispute over whether water would (does) act as a positive or negative "feedback" (multiplier effect) since water vapor and droplets (clouds) affect both incoming Solar radiation and outgoing Earth radiation.

Our simple script is logarithmic (remember our example of adding more shades over a window) but does not allow for complete saturation of radiative wavelengths, likely increases in evapo-transpirative cooling, increases in albedo (bright clouds reflecting more incoming solar radiation) nor any variation by latitude and so will progressively overestimate potential warming from CO2 alone. No matter, it does quite well enough to demonstrate the principle.

You can see how much this little script has overshot the mark since Lindzen states explicitly that a doubling from 300ppmv to 600ppmv of atmospheric carbon dioxide would result in only 0.5 °C warming. Rather obviously, Lindzen's calculations do not suggest a particularly large greenhouse influence on post-Industrial Revolution temperatures and, significantly, this does not include clouds, so CO2 would really only be a fraction of the total effect shown (Lindzen states 0.22 °C if calculated with 40% cloud cover). Despite our over-estimation of the numbers on the graph it should be apparent there is only moderate warming potential from carbon dioxide emissions. These have all been plotted simultaneously so you can see the range of estimates for incremental change in temperature driven by greenhouse gases and below we show for a quadrupling of CO2-equivalent greenhouse gas relative to pre-Industrial Revolution levels.

Update May 14: we've had a few people wonder why we "allow" claims of 40% cloud cover as though such was an outrageous claim -- what can we say? These thumbnails link to NASA's famous Blue Marble composites (low resolution versions) and you can find plenty more Earth images on their Visible Earth site. end update.

Since some people are not familiar with logarithmic effect, we'll just point out a few features from the above graphs. Note the diminishing effect in all cases -- the first half of pre-IR greenhouse-driven temperature increment in each estimate is achieved by less than 20 parts per million carbon dioxide (20ppmv CO2), it then took adding thirteen times as much again to repeat the performance (to 280ppmv). The estimated temperature increment range for a doubling of pre-IR CO2 (graphed as 300ppmv to 600ppmv) is just +0.6 °C to +1.5 °C and for a quadrupling (to 1200ppmv) +1.3 °C to +2.9 °C.

Lots of numbers, which ones fit what we think we know of the Earth's greenhouse effect?
Let's try working backwards for a moment. The Earth's greenhouse effect is commonly estimated at 33 °C and these calculations simply assume that to be true. If water vapor accounts for 70% and clouds another 20% then we have 10% left for carbon dioxide and the ubiquitous "other" GHGs. Lindzen's 3.53 °C cooling potential for complete removal of CO2 would then seem to fit the bill fairly adequately at around 10.7% of the total effect, while there's really not room for the larger estimates. Note, however, that carbon dioxide is generally reckoned to account for between 4.2% and 8.4% of Earth's greenhouse effect because water vapor and clouds also behave differently at different concentrations and temperatures (we warned you this wasn't linear).

If, on the other hand, we assume Charnock and Shine are closer to the mark then ~36% of Earth's greenhouse effect would be driven by CO2. This is intuitively unreasonable since water is both prolific and has absorption windows overlapping those of carbon dioxide to a large extent. Given that water covers more than 70% of the globe and that the lower atmosphere over water tends to be relatively well supplied with water both as vapor and clouds and further given that water is the dominant absorber in wavelengths expected in the warmer regions, such as in the tropics where water is hugely prolific and where significant greenhouse warming occurs, it simply does not seem reasonable to expect CO2 to preferentially absorb more than one-third of the available energy. This suggests (but does not prove) that Lindzen is likely to be the nearest estimate from those we've plotted above.

Note that if you discount all other possible drivers of global temperature change -- meaning that humanity has completely taken over from all natural effects that were operating until that time (highly unlikely) -- then the estimate of Charnock & Shine neatly fits observed warming over the period. If their massive estimate of greenhouse effect from carbon dioxide is true then a worst case doubling of atmospheric carbon dioxide will still only produce a total warming under 1.5 °C (and we're thought to be almost half-way there already). This still does not suggest a major enhanced greenhouse catastrophe.

If that's all the anticipated greenhouse effect, where do the big warming estimates come from?
Ah, this is where it gets rather contentious because the big warming numbers come not from measurements but from computer models. These computer models and their output are passionately defended by the modeling clique and frequently derided by empiricists -- but the bottom line is that models make an enormous range of assumptions. Whether all the assumptions, tweaks and parameter adjustments really collectively add up to a realistic representation of the atmosphere is open to some conjecture (current climate models do not model "natural" climatic variation very well), but there is no evidence yet that they can predict the future with any greater certainty than a pack of Tarot cards. Moreover, humans do a lot besides emitting greenhouse gases, changing vegetation and transpiration rates through agriculture, for example, and many effects expected to both increase and decrease regional temperatures are not included in these models.

Regardless, climate models are made interesting by the inclusion of "positive feedbacks" (multiplier effects) so that a small temperature increment expected from increasing atmospheric carbon dioxide invokes large increases in water vapor, which seem to produce exponential rather than logarithmic temperature response in the models. It appears to have become something of a game to see who can add in the most creative feedback mechanisms to produce the scariest warming scenarios from their models but there remains no evidence the planet includes any such effects or behaves in a similar manner.

Update May 14: There has been some claim we are ignoring "self-evident" positive feedbacks, which we'd be delighted to highlight if only someone could point to any such empirical measure. The bottom line, however, is that the IPCC estimates a trivial 0.6 °C ± 0.2 °C warming during the Twentieth Century and both the GHCN-ERSST Data Set and the HadCRUT2v Data Set record the period of the 19-teens through mid-1940s as having a global trend of +0.13 °C/decade for a net warming of 0.45 °C -- leaving a mere 0.15 °C ± 0.2 °C net warming potential for the post-WWII period of significant carbon emission from fossil fuel use. It is evident, to us at least, that if positive feedback mechanisms exist (entirely plausible) then their effect is negligible or mitigated by negative feedback mechanisms (equally plausible). Unlike modelers, who alter their virtual worlds at whim, we can only measure what the world actually does, and there simply isn't room in the measured change for the existence of significant unmitigated positive feedbacks. -- end update.

As an example of how mileage may vary, as they say, we've reproduced here a table of comparisons between 108 model guess-timations for a doubling of atmospheric carbon dioxide compiled by Kacholia and Reck, published in 1997. Note that the range spans from 0.2 °C to 6.3 °C and that the same modelers get large variations as they play with their model parameters, e.g. Washington and Meehl show listings of 1.3 °C; 1.4 °C–3.5 °C; 1.6 °C; 4.0 °C and back to 1.6 °C over the course of a decade (not highlighted as being egregious or any such thing, just frequent in this list). Charnock and Shine appear in this list (1993) with estimations of 1.5 °C–2.4 °C and we derive their 1995 discussion in Physics Today as 1.46 °C so we're in the ballpark and they may have reduced their estimate as Lindzen seems to have done, listed here from 1982 as 1.46 °C–1.93 °C and stating explicitly in the same Physics Today discussion that he estimated 0.5 °C for clear sky conditions and just 0.22 °C when including 40% cloud cover.

Unfortunately there has been no narrowing of the estimated range of "expected" warming from a doubling of CO2 -- in fact the range has widened even further as ever more players attempt to stand out in a crowded publication field. It isn't that the physics of carbon dioxide's radiative properties keep changing, rather that ever more imaginative "feedbacks" are shunted into the positive column to make model output more interesting. The bottom line is that you need to stuff a huge amount of CO2 into the atmosphere to get much response as more of the absorptive bands near saturation.

Why do we suspect the big warming numbers are likely wrong?
Actually, you can play with some parameters and work it out for yourselves. Since the really big guesses made by the IPCC and some truly bizarre output by climateprediction.net (CPN) are at least linear, if not exponential in their response to changes in minor trace gases we can work backwards and below you will find a pair of calculators so you can have a go.

Update: we didn't even manage to post this yet and poor old CPN has suffered a major embarrassment: Error discovered in the BBC Climate Change Experiment. So now even they know they're wildly over-guess-timating. The BBC is advising those they dragooned into the project that their model runs will be restarting here. Meanwhile, Red Tops like The Inquirer are mischievously postulating "With around 200,000 PCs running the experiment non-stop for two months, it looks very much as if the BBC experiment is making more of a contribution to global warming than scientific knowledge." Fortunately, the real world is not so easily perturbed. End update.

At left we have a linear calculator. To know how it works you just have to remember that the Earth is about 15 °C, so that's the output target you are aiming at producing at the bottom of the calculator. You know that carbon dioxide accounts for something less than 10% of the Earth's greenhouse effect so your first input is going to be a number less than or equal to that (in fact, we've limited the calculator so any greater input will be calculated as 10% and it will ignore any attempted input that is not greater than zero). The second parameter is the guess-timated warming. The output produced will be what the current global mean temperature must be for the linear increase to be as input.

At right we have a logarithmic calculator so you can play with the atmosphere to your heart's content. The calculator will always assume a base of 33 °C for the starting net greenhouse effect - it's limited to a max of 10% greenhouse effect from CO2 and a minimum of 2ppmv CO2 so you can really have a play with the atmosphere and logarithmic effect. Notice how doubling small concentrations of carbon dioxide gives large responses while the reverse also applies - enjoy! When you are finished we have some more information below the calculators.




How did you go? No? Oh well, try 4.2% of greenhouse effect for a net warming of 1.4 °C for the linear calculator.

Well, why is the planet warming so catastrophically if it's not CO2 then?
Who says it is warming catastrophically? Humans have only been trying to measure the temperature fairly consistently since about 1880, during which time we think the world may have warmed by about +0.6 °C ± 0.2 °C. As we've already pointed out, the estimate of warming is less than the error margin on our ability to take the Earth's temperature, generally given as 14 °C ± 0.7 °C for the average 1961-1990 while the National Climatic Data Center (NCDC) suggest 13.9 °C for their average 1880-2004. We are pretty sure it was cold before the 1880 commencement of record and we would probably not handle the situation too well if such conditions returned but there has been no demonstrable catastrophic warming while people have been trying to measure the planet's temperature. If we have really been measuring a warming episode as we think we have, then setting new records for "hottest ever in recorded history" should happen just about every year -- although half a degree over a century is hardly something to write home about -- so there's really nothing exciting about scoring the highest number when looking at such a short history.

At risk of belaboring the point, the following data is from the merged land air and sea surface temperature data set (based on data from the Global Historical Climatology Network (GHCN) of land temperatures and the Comprehensive Ocean-Atmosphere Data Set (COADS) of SST data). This is the Time series: Temperature January-December, 1880 - 2005: Global Trend: 0.04 °C/decade (for the arithmetically-challenged that's 12.5 decades for a total of +0.5 °C since 1880). The land temperature-only data (less than 30% of the planet and usually measured around cities) yields a trend of 0.07 °C/decade over the same period for a total increment of 0.875 °C.

A lot of people seem to like an idea of a specific temperature number so here's the National Climatic Data Center's monthly mean temperature record. Rather obviously seasonal change throughout the year dwarfs net increment over one and one-quarter centuries.

While we are talking about thermometry and measured near-surface temperatures we must underline that these accumulate to mere estimates and are fraught with difficulties. Seven-tenths of the globe's surface is water and historical temperature series from these regions are largely based on sailors tossing a bucket on a rope over the side and then dangling a thermometer in the water hauled aboard, so coverage is basically from sea lanes and measurement somewhat, shall we say, agricultural. Then there's the problems introduced by discontinuity in local records as observation points move over time or small towns cease to exist altogether, even gardens or the growth of adjacent trees might influence how air flows around a specific recording point and then there's changes in equipment to take into account. Calculating what the temperature is, let alone what it has been, is no trivial task and then accumulating myriad changing locales to a global amalgam leaves much room for error.

We briefly mentioned above that much of the temperature record is derived from measurement taken where people happen to be and thus there is an increasingly urban nature to the temperature record as rural recording sites have ceased to operate, especially over the last three decades or so. To some extent this is due to meteorological satellites as there is no longer a need to maintain remote observation outposts for the purpose of deriving surface-based weather forecasts, hence the urbanization of the near-surface temperature record. The significance of this is that there is an increasing difference between the temperatures found in the built environment and surrounding land surface - it's called the Urban Heat Island Effect (UHIE). Berkeley Lab have a good example here.

To what extent UHIE is influencing the global temperature trends we think we are measuring remains uncertain. Although curators of global temperature datasets tend to claim the effect has been eliminated through adjustments to the record, or that it is irrelevant, such claims are not entirely convincing.

There are regions where temperature records have been maintained for much longer than the 1880 commencement usually seen and these make interesting comparators. Additionally, we have some available rural and urban records from similar regions that can be viewed in parallel where we might expect similar trends if urban influence has genuinely been removed from the record. Alongside we have an example of the Armagh Observatory and Central England Temperature trends compared. Since there is no obvious reason carbon dioxide would behave differently in Northern Ireland than it does in Central England we must at least entertain the suspicion other factors are in play.

In addition to relatively subtle disparity in trends between locations we have measurements which are likely less influenced by UHIE, those taken actually in the atmosphere by instrument packs carried aloft by meteorological balloons. At left is the radiosonde record from 1958-2004 (latest we have available).

At right we have the Alaskan surface record classically highlighting the effect of the PDO phase shift. There is no plausible means by which accumulating greenhouse gas could effectively act as a major warming agent in one year but not in the preceding or subsequent years. There are many other datasets and attempts at measuring the temperature of the Earth ranging from satellite-mounted Microwave Sounding Units (MSUs) to meteorological station near-surface thermometer records and a comprehensive collection of these can be found here on JunkScience.com.

We would be remiss if we did not at least mention the infamous "hockey stick" representation of global temperature as estimated for Earth's recent history. The graphic linked at left comes from the IPCC's Third Assessment Report (TAR). The red "blade" section of the graphic is the same data as depicted in red on the graphic linked below, right and serves as an object lesson - always check the scale of depiction.

Notice that the graphic does not show absolute Central England Temperature as does the Armagh comparison above. Of particular significance is that the CET contains abrupt warming episodes of similar or greater magnitude early in each of the previous centuries. While it appears that the CET makes a fair proxy for Northern Hemisphere temperatures as derived by Jones and Mann this is merely speculative and constitutes no proof. It does, however, suggest great caution is warranted before attempting to extrapolate trends from a mere century or so of temperature data.

What caused the apparently massive temperature leap at the beginning of the 18th Century? It certainly wasn't industrialization, that hadn't happened yet. If such changes appear in the record during recent periods when people can not have caused them then they are by definition "natural" and, if such natural changes are evident in recent history, why are we so fixated on carbon dioxide as a "culprit" driving lesser warming now?

Finally, it is worth wondering why, with some three and one-half centuries of population growth, development and urbanization depicted in the Central England Temperature series, recent "chart-toppers" have managed to elevate top temperatures by a paltry 0.16 °C over those of the early 1730s. The vast majority of increase in atmospheric carbon dioxide has taken place over the seventy years since the Second World War and if CO2 were a significant driver of temperature change we would expect those years to be almost exclusively represented in the highest temperatures and yet fewer than half manage to make the warmest one-hundred list. The post hoc ergo propter hoc association of carbon dioxide is observed to increase, warmer temperatures are measured, therefore carbon dioxide warms the planet is a very poor basis for the current fixation.

So, humans aren't affecting the planet or its temperature.
Whoa! We didn't say that at all. This discussion is on greenhouse effect and possible enhanced greenhouse, but that's a long way from anthropogenic effect in total. Whether or not they really affect global mean temperature, human endeavors have significant local effects. The heat island effect mentioned above or the local effect of increased water vapor from large scale irrigation schemes would be good examples. Then there's land use change which can be variable depending on latitude -- replacing dark forest with wheat fields might significantly affect local albedo and cooling one region while denying shade in a more heavily irradiated region might cause ground heating through increased absorption. There are many effects in a hugely complex system, some will be negative, some positive and all represent change, although that is neither good nor bad in and of itself. That humans affect the region of their activities is true -- that enhanced greenhouse from human activity is known to be a current or imminent catastrophe is not. And this document is only dealing with greenhouse effect and "global warming."

What are the take-home messages:
The temperature effect of atmospheric carbon dioxide is logarithmic, not exponential.
The potential planetary warming from a doubling of atmospheric carbon dioxide from pre-Industrial Revolution levels of ~280ppmv to 560ppmv (possible some time later this century - perhaps) is generally estimated at less than 1 °C.
The guesses of significantly larger warming are dependent on "feedback" (supplementary) mechanisms programmed into climate models. The existence of these "feedback" mechanisms is uncertain and the cumulative sign of which is unknown (they may add to warming from increased atmospheric carbon dioxide or, equally likely, might suppress it).
The total warming since measurements have been attempted is thought to be about 0.6 degrees Centigrade. At least half of the estimated temperature increment occurred before 1950, prior to significant change in atmospheric carbon dioxide levels. Assuming the unlikely case that all the natural drivers of planetary temperature change ceased to operate at the time of measured atmospheric change then a 30% increment in atmospheric carbon dioxide caused about one-third of one degree temperature increment since and thus provides empirical support for less than one degree increment due to a doubling of atmospheric carbon dioxide.
There is no linear relationship between atmospheric carbon dioxide change and global mean temperature or global mean temperature trend -- global mean temperature has both risen and fallen during the period atmospheric carbon dioxide has been rising.
The natural world has tolerated greater than one-degree fluctuations in mean temperature during the relatively recent past and thus current changes are within the range of natural variation. (See, for example, ice core and sea surface temperature reconstructions.)
Other anthropogenic effects are vastly more important, at least on local and regional scales.
Fixation on atmospheric carbon dioxide is a distraction from these more important anthropogenic effects.
Despite attempts to label atmospheric carbon dioxide a "pollutant" it is, in fact, an essential trace gas, the increasing abundance of which is a bonus for the bulk of the biosphere.
There is no reason to believe that slightly lower temperatures are somehow preferable to slightly higher temperatures - there is no known "optimal" nor any known means of knowingly and predictably adjusting some sort of planetary thermostat.
Fluctuations in atmospheric carbon dioxide are of little relevance in the short to medium term (although should levels fall too low it could prove problematic in the longer-term).
Activists and zealots constantly shrilling over atmospheric carbon dioxide are misdirecting attention and effort from real and potentially addressable local, regional and planetary problems.
Remember: Water vapor and carbon dioxide are major greenhouse gases. Water vapor accounts for about 70% of the greenhouse effect, carbon dioxide somewhere between 4.2% and 8.4%. Much of the wavelength bands where carbon dioxide is active are either at or near saturation. Water vapor absorbs infrared over much the same range as carbon dioxide and more besides. Clouds are not composed of greenhouse gas -- they are mostly water droplets -- but absorb about one-fifth of the longwave radiation emitted by Earth. Clouds can briefly saturate the atmospheric radiation window (8-13µm) through which some Earth radiation passes directly to space (those hot and sticky overcast nights produce this effect - that is greenhouse but has nothing to do with carbon dioxide). Greenhouse gases can not obstruct this window although ozone absorbs in a narrow slice at 9.6µm. Adding more greenhouse gases which absorb in already saturated bandwidths has no net effect. Adding them in near-saturated bands has little additional effect.

Here's a very simplified graphic on atmospheric absorption. And, at right, there's a somewhat more detailed graphic.

Right: (a) Normalized blackbody curves for 5780 K and 220 K, plotted so that irradiance is proportional to the areas under the curves. (c) Atmospheric absorption in clear air for solar radiation with a zenith angle of 50 degrees and for diffuse terrestrial radiation. (b) Same as (c) but for the portion of the atmosphere lying above the 11-km level, near the middle latitude tropopause. [From Wallace and Hobbs, p. 332]

Finally, here's a palm-size reference version for those pub trivia nights.



So, now you know. You can see how much warming you can save via "carbon offsets" here and get an idea on solar influence here.

[Rapunzel]

You'll need to click on the link provided above in order to view the many graphs referenced in the article.

Since I know a lot of people didn't bother to read the above article I will just repost the conclusions. (Don't argue with the conclusions unless you have actually read the evidence leading to said conclusions. ).

-The temperature effect of atmospheric carbon dioxide is logarithmic, not exponential.

-The potential planetary warming from a doubling of atmospheric carbon dioxide from pre-Industrial Revolution levels of ~280ppmv to 560ppmv (possible some time later this century - perhaps) is generally estimated at less than 1 °C.

-The guesses of significantly larger warming are dependent on "feedback" (supplementary) mechanisms programmed into climate models. The existence of these "feedback" mechanisms is uncertain and the cumulative sign of which is unknown (they may add to warming from increased atmospheric carbon dioxide or, equally likely, might suppress it).

-The total warming since measurements have been attempted is thought to be about 0.6 degrees Centigrade. At least half of the estimated temperature increment occurred before 1950, prior to significant change in atmospheric carbon dioxide levels. Assuming the unlikely case that all the natural drivers of planetary temperature change ceased to operate at the time of measured atmospheric change then a 30% increment in atmospheric carbon dioxide caused about one-third of one degree temperature increment since and thus provides empirical support for less than one degree increment due to a doubling of atmospheric carbon dioxide.

-There is no linear relationship between atmospheric carbon dioxide change and global mean temperature or global mean temperature trend -- global mean temperature has both risen and fallen during the period atmospheric carbon dioxide has been rising.

-The natural world has tolerated greater than one-degree fluctuations in mean temperature during the relatively recent past and thus current changes are within the range of natural variation. (See, for example, ice core and sea surface temperature reconstructions.)

-Other anthropogenic effects are vastly more important, at least on local and regional scales.

-Fixation on atmospheric carbon dioxide is a distraction from these more important anthropogenic effects.

-Despite attempts to label atmospheric carbon dioxide a "pollutant" it is, in fact, an essential trace gas, the increasing abundance of which is a bonus for the bulk of the biosphere.

-There is no reason to believe that slightly lower temperatures are somehow preferable to slightly higher temperatures - there is no known "optimal" nor any known means of knowingly and predictably adjusting some sort of planetary thermostat.

-Fluctuations in atmospheric carbon dioxide are of little relevance in the short to medium term (although should levels fall too low it could prove problematic in the longer-term).

-Activists and zealots constantly shrilling over atmospheric carbon dioxide are misdirecting attention and effort from real and potentially addressable local, regional and planetary problems.

[PrincessFiona]

It's called junkscience.com for a reason...and not the one you're thinking 'punzel


Seriously...this article is so full of slightly twisted information and I just don't have time to pick it apart today. Grab an article from a peer-reviewed journal and let's pick that one to pieces.

kris

[Rapunzel]

Unfortunately scientists can censor their peers in peer reviewed journals. The journal "Nature" proved that.

This article makes a basic point that current peer reviewed articles based on speculative computer models are ridiculous - and they are definitely not good science (and, definitely nothing beyond mere hypotheses - yet to be tested because they are attempts to predict the future based on information that can not be complete due to the nature and complexity of the subject matter).

And, as to the op's original article: Again, I say correlation does not equal causation.

[Rapunzel]

And, let's not forget the peer reviewed research of South Korean Hwang Woo-suk’s. He managed to blatantly lie about his research on stem cells and have it found credible by peer review. The truth was his research findings fit the opinions of the reviewers who wanted to believe in it.

What we're dealing with in many instances is faith on the part of the scientific community. In some ways parts of science have become like religion to many (especially those in the scientific world) in that those portions of science are held inviolate. Which, given the nature of scientific inquiry, is ridiculous. There should be no sacred cows in science. It should be open completely and utterly to critique and dismemberment. But, this is, increasingly, the opposite of reality.

Instead, we see suppression of thought that falls outside of what is considered "acceptable" according to the opinions of scientists in positions of influence. Put another way, the Galileo's of today would be castigated just as readily by the current scientific establishment as much as any religious establishment.

So, the article I quoted makes a criticism of pop-science. And, rather than addressing that criticism it is dismissed because it falls outside the belief parameters of the popular faith of modern scientists.

The following article gives a compelling look at censorship among scientists:

http://landshape.org/enm/peer-censorshi ... fic-fraud/

[Rapunzel]

Another essay on the subject of peer censorship in science:

http://www.suppressedscience.net/inerti ... ought.html

Beginning excerpt:

New ideas in science are not always right just because they are new. Nor are the old ideas always wrong just because they are old. A critical attitude is clearly required of every scientist. But what is required is to be equally critical to the old ideas as to the new. Whenever the established ideas are accepted uncritically, but conflicting new evidence is brushed aside and not reported because it does not fit, then that particular science is in deep trouble - and it has happened quite often in the historical past. If we look over the history of science, there are very long periods when the uncritical acceptance of the established ideas was a real hindrance to the pursuit of the new. Our period is not going to be all that different in that respect, I regret to say.

I want to discuss this danger and the various tendencies that seem to me to create it, or augment it. I can draw on personal experiences in my 40 years of work on various branches of science and also on many of the great controversies that have occurred in that same period.

And, here's another:

http://www.suppressedscience.net/censor ... icine.html

Excerpt:

One esteemed scientist turned pariah because he refused to stop questioning a dogma (that HIV causes AIDS) is Dr. Peter Duesberg. He once was considered a top retrovirologist, the first to isolate a cancer gene, California Scientist of the Year in 1971 and recipient of an Outstanding Investigator Award from the US National Institutes of Health in 19861 . For 25 years he had every grant application approved.

That ended in 1987 when he published a paper providing extensive evidence that HIV could not cause disease2 . Since then he has had 0 of 23 government grants approved for research in AIDS and cancer and great difficulty getting his work published.

Duesberg’s mirror image is Robert Gallo, widely revered as a co-discoverer of HIV, yet with an entire book devoted to documenting his shoddy and corrupt science3 . The scientific establishment shuns Duesberg and his ideas, yet treats Gallo’s questionable work as the foundation of a multi-billion dollar research program.

[fluffhead]

(against my better judgement....here we go again...)
Just because the godless scientists have advanced the theory (yes, it's just a theory, like plate tectonics, macroevolution, or relativity. not a law. yet.) of global warming, does not automatically make it false.
And just because the pro-industrial right have railed against it, does not mean that all conservative religous types should jump on that bandwagon.
And just because the longhaired liberals have embraced it, does not make it patently evil.

The Greenhouse Effect is accepted. It is the reason we can live on earth. If not for the greenhouse effect we would all be Very Very Cold.

The theory of global warming posits that increased production of greenhouse gases, might increase the greenhouse effect, and thereby cause higher temperatures on Earth. Sounds logical. Other random and nonrandom effects might counter this trend, such as volcanos, general cooling trends, etc. We can't be sure of these other effects, but it would seem wise to me not to mess with the temperature on our planet. If we're descending into another ice age, so be it, but I can't be certain of it. I'd be cautious, though, of taking my hummer to the supermarket around the corner, if it's gonna make Las Vegas into beachfront property.

I love science too. I don't censor any opinions, but this is just logical, you know?

[PrincessFiona]

So..with dinner behind us, I've decided to take some time to answer this (before I tackle Andrew's science fair project with him).

First off...I obviously can't touch every main point in these pages of articles...
The greenhouse effect is what naturally keeps the earth warm. The atmosphere trapping gasses is a normal and necessary process to sustain the temperature on this planet. CO2, methane...water vapor... We want and need that. Increases in greenhouse gasses though can result in less heat escaping back to space and sticking around for us.

Do the greenhouse gasses trap radiant heat?

Yes. Only a small portion of heat that is reradiated makes it back to space. The longwave radiation is indeed absorbed by the greenhouse gasses and this results in an increase in the temperature. Again...great big DUH, but this is how we have warmed our planet up to make it inhabitable to us. It seems to work for him when it comes to raising the planet's temperature to a habitable level....

Basically, this guy says there is no green house effect until there is a green house effect to keep us warm and then there is no green house effect again because he doesn't like the name greenhouse because it reminds him of a barrier of sorts.

Regarding the idea of reradiation. I understand that he doesn't like some of the big words...but...basically, reradiation is referring to the idea that the radiation energy from the sun warms the earth and then the heating of the ground causes the earth's surface to become a radiator of heat...the earth's surface then emits longwave bands (infrared radiation) that are indeed absorbed by the greenhouse gasses and do indeed cause heating.

There...we've gotten through that painful little bit.

OH...and just because water vapor makes up more of the greenhouse gasses does not mean that the small amount of CO2 (proporionally) can't have a larger effect when it comes to absorbing energy.

Regarding CO2 *sinks* I think the big word sequestration sounds a bit better though..perhaps we can email the author and let him know....Yes, we are fortunate that right now a large portion of our CO2 is absorbed.

The rainforests are one...but...they actually aren't as good as one would think because the ongoing decomposition and fires release so much back into the environment.

The ocean is the biggest sink known thanks to little plankton who basically take the CO2 to the bottom of the ocean with them when they kick the little plankton bucket. Of course, there are limitations (like...the fact that it can take thousands of years to sequester carbon in the ocean!).

The amount of CO2 that can be absorbed is dependent on the amount of Carbonate available and how acidic the ocean is....CO2 is better dissolved in cold water (that's why your diet coke can lose it's fizz in the TX heat) and so the colder waters of the bottom of the ocean are ideal for it. The CO2 on the ocean floor is not just dumped there in little plankton packets, tucked away, never to be seen again. It is utilized by bacteria that eat the dead little plankton up and re-release the CO2 back into the water....

CO2 in water....acid-base refresher anyone?

OH..and the CO2 is also re-released in upwellings...It's not gone forever, like this guy implies.

NOW...if you're going to go all peer censorship on us, can I refer you to:

http://www.cbsnews.com/stories/2006/03/ ... 5985.shtml
Oh wait, that's cbs...the evil new's channel

http://www.npr.org/templates/story/stor ... Id=1683040
Bummer, NPR...the hippy-tree-huggers

Ahhhhhhh...here's one from a reputable source


http://www.foxnews.com/wires/2006Nov01/ ... ng,00.html

Sure, you can point to some problems with some scientists....but a few bad eggs don't mean we should kill the chicken.

Kris

PS...ignore my sarcasm :>

PS...ignore my sarcasm :>

Kris - that should be your new siggy line.

[Meenah]

Grab an article from a peer-reviewed journal and let's pick that one to pieces.

I must say that I have a new appreciation for "evidence based and peer-reviewed" now that I am almost done with my NP. It is essential for weeding out all of the BS.

[Ravenclaw]

Latest report on the climate:

http://www.cnn.com/2007/TECH/science/01 ... index.html

[PrincessFiona]

Ohhhh...those blasted liberals and their global warming.



:>

What did my step mom say to me a couple of weeks ago? "HA..we have snow in Texas...as if there was global warming" Apparently, she missed the part where global warming can have a huge impact on global climate including bizarre things like snow in TX and horrible storms in europe.

The earth will live on long after we are all extinct....

kris