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The human fingerprint in global warming

Posted on 29 March 2010 by John Cook

In science, there's only one thing better than empirical measurements made in the real world - and that is multiple independent measurements all pointing to the same result. There are many lines of empirical evidence that all detect the human fingerprint in global warming:

The human fingerprint in atmospheric carbon dioxide

That rising carbon dioxide is caused by human CO2 emissions should be obvious when comparing CO2 levels to CO2 emissions:


Figure 1: CO2 levels (Green Line - Law Dome, East Antarctica and Blue line - Mauna Loa, Hawaii) and Cumulative CO2 emissions in gigatonnes of CO2 (Red Line - CDIAC).

Confirmation that rising carbon dioxide levels are due to human activity comes from analysing the types of carbon found in the air. The carbon atom has several different isotopes (eg - different number of neutrons). Carbon 12 has 6 neutrons, carbon 13 has 7 neutrons. Plants have a lower C13/C12 ratio than in the atmosphere. If rising atmospheric CO2 comes fossil fuels, the C13/C12 should be falling. Indeed this is what is occuring (Ghosh 2003) and the trend correlates with the trend in global emissions.


Figure 2: Annual global CO2 emissions from fossil fuel burning and cement manufacture in GtC yr?1 (black), annual averages of the 13C/12C ratio measured in atmospheric CO2 at Mauna Loa from 1981 to 2002 (red). ). The isotope data are expressed as d13C(CO2) ‰ (per mil) deviation from a calibration standard. Note that this scale is inverted to improve clarity. (IPCC AR4).

Further confirmation comes by measuring oxygen levels in the atmosphere. When fossil fuels are burned, the carbon in the fossil fuels are joined to oxygen, creating carbon dioxide. As CO2 increases in the atmosphere, oxygen decreases. Observations show oxygen levels are falling at a rate consistent with the burning of fossil fuels.

Atmospheric CO2 versus oxygen
Figure 3: CO2 concentrations from Mauna Loa, Hawaii (black) and and Baring Head, New Zealand (blue). In bottom right corner is atmospheric oxygen (O2) measurements from Alert, Canada (pink) and Cape Grim, Australia (cyan) (IPCC AR4 2.3.1 adapted from Manning 2006).

The human fingerprint in the increased greenhouse effect

Satellites measure infrared radiation as it escapes out to space. A comparison between satellite data from 1970 to 1996 found that less energy is escaping to space at the wavelengths that greenhouse gases absorb energy (Harries 2001). Thus the paper found "direct experimental evidence for a significant increase in the Earth's greenhouse effect". This result has been confirmed by more recent data from several different satellites (Griggs 2004, Chen 2007).


Figure 4: Change in spectrum from 1970 to 1996 due to trace gases. 'Brightness temperature' indicates the equivalent blackbody temperature (Harries 2001).

That less heat is escaping out to space is confirmed by surface measurements that find more infrared radiation returning to earth. Several studies have found this is due to an increased greenhouse effect (Philipona 2004, Wang 2009). An analysis of high resolution spectral data allows scientists to quantitatively attribute the increase in downward radiation to each of several greenhouse gases (Evans 2006). The results lead the authors to conclude that "this experimental data should effectively end the argument by skeptics that no experimental evidence exists for the connection between greenhouse gas increases in the atmosphere and global warming."


Figure 5: Spectrum of the greenhouse radiation measured at the surface. Greenhouse effect from water vapor is filtered out, showing the contributions of other greenhouse gases (Evans 2006).

The human fingerprint in temperature trends

Another human fingerprint can be found by looking at temperature trends in the different layers of the atmosphere. Climate models predict that more carbon dioxide should cause warming in the troposphere but cooling in the stratosphere. This is because the increased "blanketing" effect in the troposphere holds in more heat, allowing less to reach the stratosphere. This is in contrast to the expected effect if global warming was caused by the sun which would cause warming both in the troposphere and stratosphere. What we observe from both satellites and weather balloons is a cooling stratosphere and warming troposphere, consistent with carbon dioxide warming:

Cooling stratosphere and warming troposphere
Figure 6: (A) Change in lower stratospheric temperature, observed by satellites (UAH, RSS) and weather balloons (HadAT2 and RATPAC), relative to period 1979 to 1997, smoothed with seven month running mean. Major volcanic eruptions indicated by dashed blue lines (Karl 2006).

If an increased greenhouse effect was causing warming, we would expect nights to warm faster than days. This is because the greenhouse effect operates day and night. Conversely, if global warming was caused by the sun, we would expect the warming trend to be greatest in daytime temperatures. What we observe is a decrease in cold nights greater than the decrease in cold days, and an increase in warm nights greater than the increase in warm days (Alexander 2006). This is consistent with greenhouse warming.

Frequency of cold and warm days and nights
Figure 7: Observed trends (days per decade) for 1951 to 2003 in the number of extreme cold and warm days and nights per year. Cold is defined as the bottom 10%. Warm is defined as the top 10%. Orange lines show decadal trend (IPCC AR4 FAQ 3.3 adapted from Alexander 2006).

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Comments 51 to 85 out of 85:

  1. JohnD, regarding historical cloud data the same folks who recovered beautiful pictures of the Moon from ancient Lunar Orbiter tapes are now doing a repeat performance w/old Nimbus weather satellite data stretching all the way back to the 1960's. They've already turned out some lovely product, some sample shots available here via NSIDC.
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  2. @50 GFW. Forgive my English, I am a Swede. I think I didn't express myself clear enough (#49). As the partial pressure of CO2 in the air has increased, so has the diffusion from air to ocean and biosphere. When our emission were smaller, some years ago, so was the partial pressure of CO2 in the atmosphere and hence the diffusion. (However the picture also includes sea-surface temperature, phytoplankton and more). It does not contradict what you call my prediction (However I would rather call it a thought experiment than a prediction). The carbon cycle is defined as flows of carbon, measured in mass (typically Giga tons). As we started to emit carbon, the carbon cycle changed. Not only the reservoars changed, but also the flows. Question: How could there be some law of nature that 50% of our emissions were to be removed from the atmosphere by oceans and biosphere? Put another way: If we doubled our emissions tomorrow, why would the oceans and biosphere increase there removal with the same increment? I still conclude that humanity has managed to keep the emission (by coincidence) about twice as large as the the net extra amount of CO2 being removed by ocean and biosphere. Thus the (about) 50% is not a constant. It can change, either if we change our emissions or if one or more parts of the carbon cycle changes. /Martin
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  3. Tarcísio #48 I am no expert, but the temperature of the CO2 at the moment of its release does not seem relevant to the carbon cycle. The molecules will be mixed up and at the same temp as the surrounding atmosphere within a few minutes.
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  4. RE# Tarcísio #48 You said:As the CO2 from the combustion, it is logical that he, for his temperature, to go position in the upper layers of the atmosphere. What I think you are referring to is how well mixed the CO2 is in the atmosphere. Alexandre is correct saying that the CO2 is well mixed. I suggest you read John's post here as this discusses further what you are referring to. As an example of pear reviewed research into this areaChahine et al 2008 has a study tracing to trace the sources and sinks of CO2 and if I quote from their conclusion: We have shown that CO2 emissions by surface sources can be observed in the mid-troposphere and how they are transported around the globe. You can also watch a NASA animation here of CO2 concentrations varying on the order of 20ppm in the mid-tropospheric. This visualization shows how it really doesn't matter where the CO2 came from, given enough time. To better quantify the movement of CO2 through these various sinks and sources the Japanese have a satellite called GOBI in orbit right now.
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  5. Oops my post is slightly pear shaped. I meant peer reviewed
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  6. @52 Martin. Well, your English is infinitely superior to my Swedish. I agree with you that we've added carbon to the "fast" reservoirs - the air, the (non-deep) ocean, plants, animals, and the soil. However through agriculture we basically control the latter three, so *almost* all the carbon we've emitted adds to the air and the ocean. (We *could* have stored more in plants if not for rainforest destruction, the pine beetle, etc.) I also agree that we've probably sped up some of the carbon cycle flows. The argument for a constant fraction going into the ocean is like this: If I take a sealed container containing salt water and an oxygen-nitrogen atmosphere, and then I inject x amount of CO2, an equilibrium will be reached with some fraction of the CO2 dissolved in the water and the rest in the air. Holding temperature constant, if I inject another x (for a total of 2x) CO2, the equilibrium will divide the CO2 into the same fractions as before: there will be twice as much in each reservoir. On our planet, there are (at least) two major changes from my little thought-laboratory. Carbon can slowly rain out to the ocean floor in the form of dead organisms, and the temperature is not constant. I would suggest that the rain-out rate is too slow to be apparent on human timescales, and that we haven't *yet* increased the temperature of the ocean enough to significantly decrease the solubility of CO2. Thus, as long as those approximations hold, the "airborne fraction" will remain constant. No, there's no particular reason for the airborne fraction to be close to 50%. It just happens that it is. If we had a dryer planet with smaller oceans, the airborne fraction would be higher (but still constant as long as the above approximations hold).
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  7. re yocta at 11:33 AM on 30 March, 2010, I find it difficult to accept that CO2 is well mixed in the atmosphere. Given the amount that is sequestered by plants and animals, or absorbed by the oceans, there must be some mechanism that causes CO2 to be driven to the surface where it is stripped from the atmosphere. Given plants are closer to CO2 deprivation rather than being able to access their optimum amount of CO2 they must be stripping CO2 as it becomes available. So is it just air movement that causes it to be replenished, or is there some other force that causes CO2 to naturally gravitate to the surface. Every molecule of carbon locked up as fossil fuels only got there by descending to the surface whatever the reason they were in the atmosphere in the first place.
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  8. @johnd #57: I find it difficult to understand exactly what you're saying here. You say you find it difficult to accept that CO2 is well mixed in the atmosphere, but go on to give a rather convincing argument that it is well mixed in the atmosphere. The very concepts of temperature and pressure in gases are closely tied to their constant motion around the atmosphere. Through this constant motion, if you release a certain volume of gas in an enclosed space, it will quickly diffuse through the whole space and end up well mixed with whatever gas was there to begin with. If you add or subtract CO2 at the earth's surface, it quickly mixes with the entire atmosphere by much the same process.
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  9. johnd, the well-mixed state of CO2 is an observed, empirical, fact. Not theory. Not based on "computer models."
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  10. johnd, in addition to the excellent links yocta gave you, see "CO2 Measurements are Suspect".
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  11. RE: johnd #57 Play around with this java animation of particles in two different boxes to see what is meant by gases mixing. At room temperature a single gas molecule undergoes approximately 10 to the power of 10 collisions per second so the diffusion of the gases happens very quickly. Whilst the atmosphere is not a simple box and there are more forces at play this helps us understand what is going on. Definitely watch the other animations on John's page that Tom Dayton linked to.
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  12. By saying not well mixed I mean that there must be either a constant movement of CO2 towards the surface to replace the CO2 stripped from the atmosphere, or else it tends to congregate closer to the the surface. If CO2 is such an efficient absorber of IR radiation should it not have a tendency to rise away from the surface rather than gravitate towards it. Water vapour only returns to the surface once it has dissipated heat previously absorbed. Does CO2 function differently?
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  13. @62 johnd. There is ongoing flow in and out of the atmosphere at the same time. Plants take up CO2, animals and decomposition release it. Prior to the industrial revolution you would have found each of the flow pairs air<->sea and air<->plants/animals/ground to be in near perfect balance. In the modern world there's a net flow from burning fossil fuels into the air, and a net flow about half that from the air into the ocean. Therefore you will find a *slight* average gradient with higher concentrations over land and lower concentrations over water. (And of course higher gradients very close to point sources like smokestacks.) Nonetheless, the term "well mixed" is still accurate. On your last point, while it's true that hot air rises and cool air sinks, that applies to gases in bulk, not so much individual molecules. When an IR absorbing molecule absorbs a photon from the ground, it either re-radiates it (randomly in any direction, thus half "down") fairly quickly, or it transfers energy to the other molecules (mostly N2 and O2) around it through thermal motion. So all the air warms up, not just the CO2 ... so the atmosphere remains well mixed, not separating out by molecular type.
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  14. @johnd #62: Yes, there is a constant movement of CO2 towards the surface. In fact there's a constant movement of every gas in the atmosphere in every direction. That's the nature of gases. CO2 collides with other molecules and distributes the heat rather quickly, so it doesn't warm beyond the surrounding atmosphere itself. And water isn't the best analogy here, since carbon dioxide doesn't precipitate down to the surface like water does.
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  15. @56 GFW So first year you inject x Gt: 0,5x will be dissolved Second year you inject 2x Gt: x will be dissolved, Third year you inject 3x Gt: 1,5x will be dissolved... (so far I agree to what has happened) But then I say: If you the fourth year inject 6x Gt: Around 2x will be dissolved, not 3x. Or if you the fourth year inject 0x Gt: Still around 2x will be dissolved (not 0x). The ocean does not know how much we emitted to the air, nor does it dissolve a certain amount direct connected to our emissions. The solubility of CO2 in oceans is a function of the concentration of CO2 in the air (and temperature etc), not primarily related to the human emission itself. (Yes I know our emission affects the concentration in the atmosphere, but so does phenomena like forest fires, emissions from soil, ocean etc. None of them are constant.) Nature itself emits huge quantities of CO2. And the net sum absorbed (in Gt) by ocean, biosphere etc is just slightly larger than what is emitted by ocean, soil, biosphere etc. The difference between these large numbers (about 216 and 212 Gt C (i.e. 4 Gt C) is the net carbon absorbed. It happens to be about 50% of our emissions (total human fossil emission was about 8 Gt of carbon in the 1990s). Check out IPCC AR4WG1 ch 7.3.1.2 IPCC AR4WG1 ch 7.3.1.1 and 2 . If we double our emissions, the concentration in the air does not double. If we cut our emissions by 100% (no emissions), the oceans would still absorb about the same amount (in Giga tons, not %) as it did last year. It is tempting to see our emissions with some decay rate, like radioactive decay. But it is not. We add carbon to the cycle. The absorption of carbon in the ocean is a function of the carbon cycle, not the human emissions. In an non-changing environment its solubility in oceans could behave like a decay rate, but it still is not. And as the climate, ecosystem, ocean temperature etc change, it is highly unlikely that the airborne fraction (about 43%) of anthropogenic CO2 would stay constant. If humanity wanted to decrease the concentration of CO2 in the atmosphere, we would have to decrease the emissions by more than approximately 43%. Hence more CO2 would be dissolved/absorbed by ocean and biosphere than we and nature emit to the atmosphere. If we cut our emissions by 50%, the airborne fraction would be -14% (-7 of the 50%-units emitted) for the first years (until carbon cycle changed). Or put it another way: Humans + nature would emit less to atmosphere than nature extracts from the atmosphere. But we have to do this well before there was a risk that CO2 solubility in oceans changes, for example due to the rising temperature in the ocean. (or methane outburst, or albedo changes, or... changes) And then we have ocean acidification... Is it a good or a bad thing (from humanities point o view) that CO2 is dissolved in the oceans? It gave us time, but we used the time to build up potentially larger problems. Maybe this conversation should have been at the blog post: Airborne fraction of CO2 here at Sceptical science. Sincerely, /Martin
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  16. re GFW at 15:56 PM on 30 March, with regards to your comment about gases in bulk, warm gases rising etc, all CO2 produced by burning fossil fuels leaves the combustion at an elevated temperature. I expect that it then both rises and begins dissipating heat energy until it acquires equilibrium with the surrounding air. At what point would the now cooled CO2 begin re-absorbing IR radiation, and if it was to re-radiate it downwards to the surface, where has the surface heat dissipated to that allows a temperature differential to develop between the warmer CO2 and the cooler surface. If the surface was able to cool sufficiently to create such differential by dissipating it's heat energy upwards, why then was the CO2 not also dissipating it's heat energy in the same direction and at the same rate as the surface? In fact should not gases such as CO2 reach equilibrium faster than the surface?
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  17. Martin Hedberg, there is a relevant post on RealClimate, about a new paper describing how fast CO2 levels would drop if human emission suddenly went to zero: Climate Change Commitments. And I think you're right that more conversation on this topic should happen over at the thread Airborne fraction of CO2. Other folks will notice your comments and follow you there.
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  18. I'm a little surprised that there has not been much (if any) discussion yet on the seminal fingerprinting techniques used by Santer and others. Perhaps it is because their technique relies on a combination of observations, modelling and reanalyses (model runs constrained by observations). Regardless, Santer et al. have a few papers in which they make a very convincing case that the response of the biosphere has a marked human influence via higher concentrations of GHGs-- that is, the recent changes cannot be explained solely by internal climate variability or other natural drivers of climate. Here are some links: The human fingerprint on increase in precipitable water over the oceans The human fingerprint on changes in the height of the tropopause And another paper in Science There is also a summary here and here
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  19. Sorry folks. The PW water link @ 68 is broken. It should be: http://www.pnas.org/content/104/39/15248.full The link for the NERSC summary is also broken: http://www.nersc.gov/news/annual_reports/annrep03/advances/5.1.fingerprints.html
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  20. To add to the upper vs lower stratosphere distinction, here's a source on this, although much of the data is somewhat out-of-date. http://www.atmosphere.mpg.de/enid/20c.html
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  21. In tracking global atmospheric composition, the implications of change goes beyond effects on Earth's temperature. In fact, climate may be the least significant issue. For instance, life (as we know it) cannot be sustained without oxygen. Mathematical projections on global ice melting, temperatures, sea level rise, etc., are commonplace on this site, yet general questions on bio-sustainability are typically avoided. And while these issue may hold a higher priority for limiting fossil fuel burning, the focus here attemps to limit itself to safeguarding the climate theory behind AGW (i.e., the relationship between CO2 levels and global warming). And with all the data and resources currently dedicated to this issue, it would seem proper to apply it to a higher purpose. Not only would there be more interest and motivation, there is a higher chance of actually acheiving goals relative to the reduction of GHG emissions.
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  22. Arkadiusz Semczyszak: The ice core with the highest resolution (8 years for 2 out of 3 ice cores of Law Dome) and a spread of only 1.3 ppmv (1 sigma). These have an overlap of about 20 years (1960-1980) with the atmospheric data taken at the South Pole. There is practically no CO2 gradient at the South Pole. Moreover, ice cores with completely different temperature profile and accumulation speed all show the same CO2 levels for the same gas age within a few ppmv. Ice core CO2 start to increase and d13C to decrease around 1850. That is at the same moment that this happens (at a different level) in the upper oceans as has been measured in coralline sponges. Stomata (index) data show the same increase in CO2 for the past century (they are calibrated... against ice cores!), but rather unreliable indicators for past changes, as they react on local/regional CO2 levels over land, which are heavily influenced by land changes over time...
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  23. Tarcisio José D'Avila at 05:14 AM on 30 March, 2010 I question the assertion that the relationship c13/c12 may indicate that the increase of CO2 in atmosphere is the result of burning fossil energy. The absorption of CO2 by oceans and plants tend to dominate the CO2 released by decomposition of organic matter (CO2 cold). CO2 of all sources is quite rapidely mixed within a few days to a few months within each hemisphere. The passing of the ITCZ (at the tropics) from the NH to the SH takes some more time, currently some 14 months to reach the South Pole. The 13C/12C ratio is a good indication of the source: besides fresh organics and fossil organics, all other sources of carbon have a higher 13C/12C (d13C) ratio. That are volcanic eruptions, carbonate rock wearing and (deep) ocean degassing. But how can we make a differentiation between fresh organics and fossil one's? There are two ways: fresh organics have some 14C built in from cosmic rays or nuclear tests. That is used for carbon dating, up to some 60,000 years. Fossil carbon is completely depleted of 14C. The decline of 14C in the atmosphere was observed around 1870 and carbon dating had to be corrected. The second method is from the oxygen balance: We know how much fossil fuels were sold (taxes!) and how much oxygen that needs. The oxygen use since about 1990 was measured and there is somewhat less used than calculated. That means that the whole organic world acts as an oxygen source, thus a (preferentially 12C) CO2 sink (photosynthesis...). Thus the decrease in d13C is from fossil fuel burning and nothing else.
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  24. RSVP "For instance, life (as we know it) cannot be sustained without oxygen." That's incorrect. The oxygen in our atmosphere is owed to living organisms. Numerous organisms still exist that do not need oxygen. See for example this: http://www.scientificamerican.com/article.cfm?id=origin-of-oxygen-in-atmosphere
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  25. "A comparison between satellite data from 1970 to 1996 found that less energy is escaping to space at the wavelengths that greenhouse gases absorb energy (Harries 2001)." The key driver here is not "that less energy is escaping to space at the wavelengths GHG absorb". The key metric is whether the overall radiation from the earth at all wavelengths is in balance with all the energy absorbed by the earth. The atmosphere/oceans/biosphere act as an insulator, slowing the rate of energy transfer from where it is absorbed to where it is emitted. They have done this for millennia, maintaining a higher temperature at the surface than we would have absent atmosphere/oceans. If the mechanisms that slow this energy transfer act to slow the energy flow further, the surface would increase in temperature with no change in the energy absorb vs that emitted. No change in the overall radiation balance is required to change the temperatures in the system, simply a change in the rates of transfer. CO2 certainly absorbs IR radiation, but how this affects the mechanisms that move the energy around in the system is far from understood, particularly when water(vapor,liquid, and ice) has such a large effect on the atmosphere and surface. The overall climate, barring catastrophic meteors and volcanoes, has remained hospitable to life for over a billion years. The reasons why this is so still don't seem to be understood.
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  26. philc, you are incorrect that "If the mechanisms that slow this energy transfer act to slow the energy flow further, the surface would increase in temperature with no change in the energy absorb vs that emitted." If the surface temperature increases, the surface radiates more energy.
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  27. philc, your comment here is a bit unclear, but it seems like a restatement of your recent comment over on another thread (Empirical evidence that humans are causing global warming). I replied to it there.
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  28. Sorry Tom, but assuming the earth in in radiative energy balance(that we aren't in thermal runaway and are doomed) the incoming and outgoing radiation have to be equal. Any mechanism that slows the transfer of energy through the atmosphere("insulation") would result in an increase in temperature within the earth's atmosphere with no permanent change in the outgoing radiation. Depending on the rates involved there might be a temporary, measurable change in the outgoing radiation, but given the large amounts of radiation involved and the large variations in already already existing measurements, it might be very hard to pinpoint. The slower the heat transfer, the larger the temperature difference that will be supported.
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  29. philc writes: Sorry Tom, but assuming the earth in in radiative energy balance [...] That's the whole point. The earth's radiant energy budget is currently not in balance -- outgoing LW radiation is less than the incoming solar radiation. This causes the planet to heat up, which in turn causes more LW radiation to be emitted. Eventually outgoing LW radiation will thus be back in balance with incoming solar radiation, but at a higher temperature (and with less LW in the CO2 absorption bands and more LW outside those bands). That's assuming that CO2 stops rising and then plateaus at some value for a long enough time for the radiation balance to reach equilibrium.
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  30. philc, maybe I misunderstood what you wrote. Increased insulation reduces outgoing radiation, causing an imbalance between incoming and outgoing. Temperature increases, increasing the radiation trying to get out, until the extra radiation trying to get out overwhelms the additional insulation, resulting in, once again, the outgoing matching the incoming.
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  31. Philc, this is one of those situations where a very simple experimental analogy can resolve a misunderstanding. The experiment's so easy to picture it's probably not necessary to do an actual implementation. But if you want to do it, you'll need an empty one gallon paint can, a thermometer, a 75 watt reflector lamp, and an old sweatshirt or other piece of cloth. -- Fill the paint can with water. -- Situate the can in a place with a stable ambient temperature -- Allow time enough for the temperature of the water to reach the ambient temperature of its location. -- Take a reading of the water temperature -- Arrange a 75 watt reflector bulb so that it is shining into the top of the can from a few inches away. -- Continue to take temperature readings, until the temperature has stabilized at its higher level. Record the stable temperature. -- Wrap the can with the old sweatshirt or cloth, leaving the top of the can and water exposed to the lamp. -- Take more temperature readings until the temperature of the water has stabilized at its new higher level. You've just seen why the Earth's temperature will rise but will not rise forever when its better insulated. The experimental analogy is not perfect because the insulation you've added to the can not only retards radiation but also reduces convective losses, but it's adequate to model the situation.
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  32. Is Chen 2007 peer-reviewed? In which journal?
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  33. Please read the argument again: "A comparison between satellite data from 1970 to 1996 found that less energy is escaping to space at the wavelengths that greenhouse gases absorb energy (Harries 2001)." The fact that GHG absorb some specific frequencies of outgoing radiation is not in doubt. What is in doubt is whether or not the TOTAL TOA radiation is in balance or not. The example in #81 is a flawed analogy. An open paint can will evaporate water, carrying away energy. Very, very little of the earth's water is evaporated into space. Insulating the can simply turns the apparatus into a version of a plain old greenhouse and doesn't speak to any of the mechanisms that slow the rate of energy flow in the climate system.
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  34. philc, put a transparent cap on the paint can and the same thing will happen; the effect does not depend on evaporation. Or can you describe why it won't? Insulating the can reduces not only convection but also causes backscattering of energy radiating from the can. Or can you explain how it does not? I'm not concerned with illustrating this situation for you, specifically, but instead for others who may be reading comments on this thread. You of course are free to believe whatever you wish, just as my cat is free to gag up the pills I give him for the hyperthyroid condition that will kill him if it goes untreated, heh!
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  35. @Bob Close, from #29, regarding: "Where is the verified experimental or actual measurements to support this strange assumption, or its corollary that ongoing atmospheric increases in CO2 above 400-500ppm will automatically create a tip over effect into runaway spiraling catastrophic warming? This critical data is now urgently required because without it one can only conclude that it is wishful thinking or worse to blame fossil fuel generated CO2 for most of the current global warming and its supposed undesirable effects. Lets get the science more exact and in perspective." Regarding the first part, do you really want to do the experiment? Well, we're doing it? Regarding the second part, yes, I agree, and that should logically be the basis for a massive increase in funding for climate science to get to the bottom of the question. There are two problems with that: First, the physics can already explain what's happening, and the mathematics say the changes *might* be catastrophic non-linear bifurcations. Second, even if that were not believed, the funding is not forthcoming. Indeed, the tendency from They Who Must Be Obeyed is to reduce funding. Pardon me if I consider the proposal a red herring.
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    Moderator Response:

    [DB] All-caps converted to bold. Please, no all-caps.

    Please note that the comment your are replying to was from 2010, not 2012.

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