TIRED OF 'GLOBAL WARMING' - 'GREENHOUSE' PROPAGANDA?

Me too.. on and on it goes.. never ending tree-huggers, pseudo-UN-scientists, and alarmists in general.. why is there never an objective contrary position?

Check out The Real 'Inconvenient Truth'

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.

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."

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.

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.

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.

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.

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."

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..

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.

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.

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.

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.

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).

Ah, we've added 2.5% to the 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.

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.

[ed note: see rest of analysis at link 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.

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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.

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.

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.