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Chris S at 18:12 PM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
Interesting that BP & johnd both seized on one paper I linked to in my earlier post (the FACE trial paper) yet apparently failed to take the rest of my advice (" In fact, that issue has several (free access) review papers on climate effects on agriculture that several commentators here would benefit from reading...") For example: http://jxb.oxfordjournals.org/content/60/10/2827.abstract Integrating pests and pathogens into the climate change/food security debate. Gregory et al. (2009) Abstract: "...Globally atmospheric [CO2] has increased, and in northern latitudes mean temperature at many locations has increased by about 1.0–1.4 °C with accompanying changes in pest and pathogen incidence and to farming practices. Many pests and pathogens exhibit considerable capacity for generating, recombining, and selecting fit combinations of variants in key pathogenicity, fitness, and aggressiveness traits that there is little doubt that any new opportunities resulting from climate change will be exploited by them..." johnd says: "Apparently apart from myself and BP few others have bothered to read any of those recommended..." I think that should read "Apparently including myself and BP few others have bothered to read..." -
scaddenp at 18:03 PM on 19 April 2011CO2 lags temperature
" If CO2 drives temperature we sgould see a corresponding droop on the low temp but we don't." Sorry, but solar IS what is drives temperature here. CO2 and albedo just amplify. Together these have no problem driving the ice age cycle using standard physics. An alternative theory has to explain a vast amount of observations including isotope signatures for methane and CO2 in ice core, spatial distribution of cooling etc etc which current climate theory does quite well. I frankly find it unbelievable that anyone can look at even the original, pre-ice core data and seriously doubt that Milankovich cycles are not involved. I suspect a few seconds on google will find you the problems with Hoyle's theory. The lack of oomph is only a problem if you are determined that GHG changes cannot affect the temperature of the planet. Does your alternative model no-GHG effect correctly predict the surface temperature of venus, earth and mars? -
johnd at 17:48 PM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
Marcus at 11:19 AM, I have a better suggestion, instead of you claiming that I have misrepresented you, why don't we all go back and examine word for word what I wrote and compare it to what you claim that I wrote and see just who is misrepresenting who. There is little humour to be had when a reader misrepresents what someone else has written, but it becomes a big joke when that reader fails to understand just what they have written and so misrepresent themselves, but worse then that, go on to attack those who faithfully quoted what was actually said. -
novandilcosid at 17:45 PM on 19 April 2011CO2 effect is saturated
Tom Curtis @ #85 has fallen into a trap. His claims are all correct. So are mine. It will be noted that I prefaced my analysis with the following words: "For a system in equilibrium (ie for the planet integrated over the surface and over a year)" Essentially this is what is claimed when the IPCC states there is 3.7W/m^2 of Radiative Forcing if CO2 is doubled. Or when a 3 DegC temperature rise is claimed. It is not for a specific location but is an average for the whole planet integrated over a year. Consider a planet 3 degrees hotter (in the above sense). The likelihood is that the relationship between the Surface and Air is the same (this is implicit in the claim of a constant lapse rate) ie the average temperature difference between the air and surface is THE SAME. So the Conductive term, which is solely driven by temperature difference will be the same. We know that a doubling of CO2 has little DIRECT effect on the absorption of surface heat - maybe about 0.5W/m^2 of increase. ie the Window to space only closes fractionally. So both these terms are nearly zero change. The equation for surface heat absorbed into the atmosphere is: Surface Heat Absorbed into the Atmosphere = Surface radiation - the portion escaping through the Window - Back Radiation + Conduction + Evaporated water We also know from the surface energy balance that, providing Conduction and absorbed solar don't change, Change in Back Radiation = Change in Surface radiation + Change in Evaporation, or Change in surface radiation - change in backe radiation = -change in Evaporation or, if radiation through the window is cobstant, Change in NET radiation from the surface into the atmosphere = - Change in Evaporation Putting this in words, any increase in evaporation is balanced by an equal and opposite reduction in Net radiation from the surface. Hope this helps. -
Tom Curtis at 17:11 PM on 19 April 2011CO2 effect is saturated
novandilcosid @84 as the situation stands, a large number of scientists using different programs on different computers have calculated the absorption, emission and transmittance for each wave number across the entire IR spectrum for the surface, plus each of 33 or more layers of atmosphere using observationally based information on temperature levels, and trace gas concentrations. In doing so they have produced spectra that almost exactly match those actually observed from space. Using these diverse models, if they increase the amount of CO2 by a factor of two, they reduce the outgoing IR radiation by approximately 3.7 Watts/meter squared. Those scientists and others, using still other computers have used equivalent techniques, but in which they allow the temperature and humidity at each layer to be set by the program based on energy balance equations and produced almost identical results. Deniers almost always ridicule these results as being "only based on models". But you want me to believe your claims about the effects of increasing CO2 based on the fact that you have calculated for just two wave numbers and just two poorly defined levels of the atmosphere. How about you program your line by line model and see if your results actually hold when you consider the whole atmosphere and all of the radiation. In the mean time, if you click on the picture below, you might get a clue:
(Atmospheric absorption for 280 and 560 ppm CO2 as calculated by DeWitt Payne using Spectralcalc; difference between values shown in 82 above.)
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novandilcosid at 16:59 PM on 19 April 2011CO2 lags temperature
KR @ 314 "The Milankovitch cycles driving the repeated glaciation of the Earth only supply a very small forcing (both up and down), not enough to change temperatures very much by themselves." That's the problem with Milankovitch - not enough oomph. All should note that Milankovitch is not the only shot in the locker. I think those who are not aware of the cosmic theory of Ice Ages should take a dekko at Fred Hoyles "Ice". This seems to me to be a more coherent and less ambiguously weak possible cause of Ice Ages. Hoyle correctly points out that these typically happen very fast - on the order of 20 years. A second alternative is the Svensmark hypothesis, again a cosmic origin. -
novandilcosid at 16:53 PM on 19 April 2011CO2 lags temperature
Scaddenp @ 316 : "Do I understand you correctly in that you are expecting co2 to drop as soon as the solar forcing drops the temperature, but that you don't see that?" No I expect to see elevated CO2 affecting the rate of Tdrop, and also drooping CO2 to affect the low temperature base. I see neither of these effects in the graphs and they should be there. Basically once temperature has fallen it generally remains flat, even though CO2 concentration is falling. If CO2 drives temperature we sgould see a corresponding droop on the low temp but we don't. -
Tom Curtis at 16:44 PM on 19 April 2011CO2 effect is saturated
novandilcosid @83 (A) claims the surface energy balance is given by: Absorbed Sunlight + Back-Radiation = Surface Radiation + Evaporated water + Conduction Clearly in doing so he is talking about the actual surface - ie the top 1 mm of dirt of water that covers the planets surface. Oddly enough, there are very few thermometers stuck into that top 2 mm, with most thermometers being stuck in the atmosphere 2 meters above that surface. The "Global Mean Surface Temperature" is actually the temperature of the lowest surface layer of the atmosphere, so the proper energy balance equation is: Absorbed Sunlight + Back-Radiation = Surface Radiation + Evaporated water (including water from transpiration in plants) + Convection Although nonstandard, we can still work with novan's actual surface. (B) Novan also claims the only way the temperature can change is if the Left Hand Side of the surface balance equation changes. This is patently false, and refuted by everyday experience. It is standard procedure in cooking to alter the heat flow or temperature of water on the stove by adjusting evaporative heat loss rather than the heating element or flame. I come from Mount Isa where it is standard practice to cool homes by using evaporative air conditioners. Further, in Australia drinking water in the outback is typically stored in canvas bags rather than Jerry Cans so that evaporation will cool the water. If, at the surface, conductive heat flow was restricted, say, by raising the temperature of the layer immediately above the surface, and the inputs were left unchanged, the surface temperature would increase. The surface air layer could be warmed by a reduction in convection (and hence also latent heat transfer) by the warming of the air layer above that, and so on till you reach the upper troposphere where the air will be warmed by a reduction in the net outgoing IR radiation from that level by an increase in CO2 levels. C) Novan purports to have proved from first principles or empirical research or to just know a priori (I'm not sure which) that conduction between the surface and atmosphere is near constant, which is false. He also claims that the change of evaporative heat loss from a surface will automatically match in magnitude, but with opposite sign the change in radiative loss of heat to the atmosphere. This principle apparently holds true whether the surface in question is rocky desert or ocean, and also to hold independently of wind speed over the surface. That is an astonishing result, and I cannot wait to see the proof. I expect to be disappointed, however, for it sounds more like magical thinking than science. -
RSVP at 16:34 PM on 19 April 2011Waste heat vs greenhouse warming
KR 396 "which it (waste heat) could only do if it didn't affect surface temperatures" Surface temperature is only skin deep. If thermal radiation was the only heat transfer mechanism, you would be absolutely correct. Conduction however leads to heat storage within solids. The warmer a thing gets, the deeper the heat penetrates, and therefore, the longer it takes to come back to the surface. There are similar considerations for fluids, especially as affects thermal water pollution. Your model completely ignores these realities. On the otherhand, you are correct to the extent that waste heat might increase surface radiation, this would help in subtracting from the overall "accumulated" energy. And referring to the analogy, perhaps that would be the effects of inflation on your pension. -
Marcus at 16:09 PM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
"In general I think extra rainfall and temperature will help C3 crops." What you *think* is irrelevant, unless you can back it up with hard *evidence* Luke. Extra rainfall is not much good if it comes after a decade of drought, & as a deluge-yet that is *exactly* what is being predicted here in Australia. warmer temperatures are likely to lead to more rapid ripening, most likely before the plants reach maximum biomass. Also, as with John D, you're choosing to ignore the potential impacts of eCO2 on both soil-borne diseases & insect pests-not to mention the impacts on weeds (which are, themselves, predominantly C3 plants). As to your claims regarding breeding new varieties-you are aware of the kind of time, money & effort that this takes, aren't you? I'd suggest that *not* stuffing up our climate would be far more cost-effective than adaptation. Still, it never ceases to amaze me the lengths some people here will go to defend the interests of the fossil fuel industry. -
Albatross at 15:10 PM on 19 April 2011Christy Crock #4: Do the observations match the models?
rhjames @12, If you did not notice, this thread is about Christy playing fast and loose with the facts and misrepresenting the science, and as a consequence misleading people. Can we assume that you agree with Christy's misinformation then? If you do not like that RC graphic, how about this one?
Sorry, Christy is still wrong.
" If I simply look at the trend over the past 15 years, it certainly looks flat, rather then increasing"
That subjective opinion would be incorrect, and is also cherry-picking, b/c 15 year sis typically not sufficiently long a period to determine a statistically significant trend from a noisy series such as the global SAT. But let us test your subjective assertion witht hat caveat in mind. Last 15 years would be 1996-2010 (inclusive). Trends from Woodfortrees.org:
HadCRUT: +0.10 per decade
GISTEMP: +0.16 per decade
RSS: +0.07 per decade.
UAH: +0.09 per decade
"I don't see a convincing upward trend."
Eyeballing a graph is not the way to do it.
"Therefore, I have to say that, at this stage, the actual data doesn't support the IPCC model trend in recent years."
That would be your opinion based on eyeballing. Please see my post @2 for some objective numbers which run counter to your opinion.
Also from Hansen et al's recent 2010 paper:
"On the contrary, we conclude that there has been no reduction in the global warming trend of 0.15°C– 0.20°C per decade that began in the late 1970s."
Really, this is getting really tired debunking these tired old unsubstantiated memes put forward by so-called 'skeptics'. And you know what, buy cherry picking short windows of time, we can do this ad infinitum, all the while convincing ourselves that it is not warming or that the warming has slowed when the reality is in fact very different. Lindzen and Motl may have gotten away with that trick once with Jones......but they are rapidly exhausting their bag of tricks to hide the incline.
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RSVP at 14:59 PM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
"... all actions so far have been futile; Does anyone have any suggestions? " Suggestions only make sense when the problem statement is properly couched. The first question... which is the bigger problem, CO2 toxicity, or climate change? I dont pretend to know the answer to this question, but getting this straight upfront might make a difference. -
Bern at 14:57 PM on 19 April 2011Christy Crock #4: Do the observations match the models?
rhjames: er, no. If we take 1995 as the starting point for your "last 15 years", then go across horizontally - a strong downward trend would have put temperatures well below the IPCC projections. And if you're not seeing a rising trend in that data, then I suggest you stop squinting and turning your head sideways to 'blank out' the grey IPCC bounds. The last time it was as cool as 1995 was back in 2000. The last 10 years have all been considerably warmer. If you want a good statistical analysis of the temperature trends over the past 35 years, I strongly recommend this post over at Tamino's blog. He removes the effects of ENSO so the underlying trend can be seen more clearly.Moderator Response: [DB] Not to mention: The last month with below-average temperature was February 1985. That makes 313 consecutive months with temperatures above the 20th Century average. Whodathunkit? -
scaddenp at 14:52 PM on 19 April 2011Christy Crock #4: Do the observations match the models?
Ditto, the guys skill at derailing threads is amazing. Did same at RC. The site was good when it discussed climate science - the politics and solutions attracts trolls. Makes you hanker for the BP of old. -
Albatross at 14:39 PM on 19 April 2011Christy Crock #4: Do the observations match the models?
Dhogaza, I share your sentiments, but what to do? IMHO, it is best invoke DNFTT. -
Clouds provide negative feedback
RW1 - Water vapor is an amplifier, a positive feedback. Clouds are a less well understood feedback; most estimates are that they are slightly positive, but not overwhelmingly so. Neither can be a driver of climate, however, since they respond so quickly to temperatures. They cannot stay consistently out of balance long enough to push anything else out of balance. Keep in mind that seasonal and aperiodic variations such as ENSO make water vapor and clouds vary hugely - they are really more amplifiers of internal variance on those time scales. As to the stability of the other possible modifiers of energy in/energy out - look to the variances and speeds there of of insolation/solar cycles, Milankovitch cycles, volcanic and other aerosol sources, ice coverage change speeds, etc. And don't forget the speed of change of anthropogenic forcings, primarily CO2. Which is changing faster than any of the other forcings, in fact faster than all the other forcings are changing combined. And which naturally responds as a feedback to temperature changes on perhaps a 500 year schedule - meaning CO2 imbalances last long enough to shift the climate energy balance and average temperatures. -
dhogaza at 14:26 PM on 19 April 2011Christy Crock #4: Do the observations match the models?
heeem... I don't see that in the plots ! actually with arctic ice, extrapolating the known curve when models were published would have given better results than the model.
Gilles reinvents the "models have been too conservative" meme in defense of his "climate science is bollocks" meme ... Now that's interesting. But, of course, he takes the half-court buzzer shot by saying:actually extrapolating the 2006 to 2007 shift of sea ice melting would have given very bad predictions for 2010
which is hilarious on the surface. There's a good reason why gilles's posts haven't showed up at RC for a long time. Really, can't we lose him? I'm reading the site less and less, and it's largely due to Gilles ... -
novandilcosid at 14:21 PM on 19 April 2011CO2 effect is saturated
Tom went on to claim that the 15um CO2 band is very wide. But examination of outgoing spectra suggests that the major CO2 effect is confined to the wavenumber 625-700 region, as does a plot of the absorption lines. In this region, the outgoing spectrum is about 15-18W/m^2. Of that around 12-15W/m^2 is being emitted above the tropopause. And that number goes up as the concentration of CO2 goes up, as the emissions come from higher in the Stratosphere (higher = warmer = stronger emission). I don't know how much emission is coming from CO2 molecules emitting the very weak lines outside this region, but not very much. I think it may be time to reveal how much energy is believed to be radiated from these weak lines, and what the exact effect of a doubling of CO2 is thought to be. [I distrust "Transmittance". How is it defined? There needs to be a distance and a concentration specified to make sense of the number. It is far more instructive and useful to use absorption tables, where the percentage remaining after passage through a specified amount of gas is defined. "Change in Transmittance" is even worse!] -
RW1 at 13:57 PM on 19 April 2011Clouds provide negative feedback
KR, Better said: What's the mechanism driving the 'extremely powerful negative feedback'??? If it's not primarily clouds through their ability to modulate incoming solar energy and precipitate water out of the atmosphere, then what is it? -
novandilcosid at 13:54 PM on 19 April 2011CO2 effect is saturated
Tom Curtis wrote: "novandilcosid takes on basic physics on the CO2 lag thread. He writes: "1. The undisputed absorption figures for CO2 mean that an increase in concentration cannot directly greatly (I mean by more than 0.5W/m^2) increase the absorption of surface energy by the atmosphere." novan calculates this by calculating the change in brightness temperature of the back radiation assuming the atmospheric temperature profile remains constant, and that the increased CO2 concentration reduces the average altitude from which the back radiation is emitted. The problem with this is not that it is in error, but what it ignores. Specifically, what heats the surface is not the back radiation but the sun. The way the back radiation effects the surface temperature is only by modulating the rate at which heat escapes, but it is a minor player in that role. Far more important is convection, which carries heat rapidly to the upper atmosphere. In the event that the upper troposphere warms, as for example, because of reduced IR radiation because of increased CO2 concentrations, that will slow the rate of convective heat transfer, and because heat is being carried away from the surface slower, the surface will warm until equilibrium is reestablished. This will result in an increase in back radiation, but because the lower atmosphere has warmed, not because of the lower effective altitude of emission of back radiation." For a system in equilibrium (ie for the planet integrated over the surface and over a year) the Surface Energy Flow Balance is: Absorbed Sunlight + Back-Radiation = Surface Radiation + Evaporated water + Conduction For doubled CO2, the Absorbed Sunlight is less by 1W/M^2 because of increased absorption in the upper atmosphere. The Back Radiation is about 0.5W/m^2 more, due to a drop in the average height of CO2 radiation (lower is hotter). So the LHS (the forcing side) is less, and unless there are any other influences the Surface will cool slightly, resulting in slightly less Surface Radiation, and slightly less evaporated water. Note there is no mechanism to change the energy balance at the surface other than by varying the absorbed sunlight or the back radiation. The Surface couldn't give two hoots about what is happening in the thin cold and radiatively isolated upper atmosphere. It can only change temperature if the LHS of the equation changes. The absorbed sunlight will change if the albedo (clouds, ice) changes, the sun changes or as in this case, the absorption into the atmosphere changes. The back radiation will change if the atmospheric window closes, or if the Greenhouse gases heat up. So I disagree with Tom in one important detail. He suggests the surface heats up because of slowed atmospheric convection, then back radiation increases because of a heated atmosphere. That's not the case. The surface temperature can only increase if the atmosphere heats up first. And I'm not sure that it does. [There are some other interesting aspects: The atmospheric window is almost constant, the conduction is almost constant, so the heat transport from the surface into the atmosphere is almost a constant whatever the surface temperature. What happens as the temperature rises is that the Net radiation (surface radiation less radiation through the window less back radiation) DECREASES and this balances the increase in water vapour condensation. It is also of interest, as Tom points out, that the surface heat transport into the atmosphere is one fifth Net radiation, one fifth conduction, and three fifths condensation of water vapour.]Moderator Response: [DB] Please do not quote more than a sentence at a time from someone else's comment. A link to their comment plus the specific point you wish to quote will be sufficient. Thanks! -
RW1 at 13:53 PM on 19 April 2011Clouds provide negative feedback
KR, "As to what changes those conditions?" I asked what's primarily controlling those conditions? What's keeping the 'boundary conditions' (power in = power out) so stable from year to year, given all those influences Sphaerica listed - specifically the water vapor, the "primary amplifier"??? "This extremely powerful negative feedback keeps the temperature within the ranges you are discussing here. What's the mechanism driving the 'extremely powerful negative feedback'??? If it's not primarily clouds through their ability to reflect sunlight and precipitate water out of the atmosphere, then what is it? -
Clouds provide negative feedback
The boundary condition is that climate energy in = climate energy out when averaged over the long term (i.e., longer than internal variations such as ENSO and yearly seasons, which is apparently about 30 years or so). As to what changes those conditions? Everything Sphaerica listed here. One critical thing is that if the response time of any influence on the energy flows to temperature is considerably shorter than the climate internal variation time frames, it can only be a feedback (responding to changes) rather than a forcing causing long term changes. Water vapor and clouds have response times << ENSO and seasons, and any internal variation in water vapor and/or clouds will get overridden by those variations. Water vapor and clouds respond to climate changes, but cannot cause them.Moderator Response: [DB] Removed "of one" text string per request. -
scaddenp at 13:40 PM on 19 April 2011CO2 lags temperature
"If temperature was being amplified proportionately to CO2 concentration then we would expect to see some influence of this on falling temperatures. " Do I understand you correctly in that you are expecting co2 to drop as soon as the solar forcing drops the temperature, but that you don't see that? Carbon feedbacks with temperature are mostly very slow. The change in solar is the driver. Once temperatures drop it takes time for the changes in the carbon cycle to remove carbon. Putting carbon back into the atmosphere when temperatures rise can happen faster (eg methane release from thawing permafrost). -
RW1 at 13:27 PM on 19 April 2011Clouds provide negative feedback
KR, What's controlling the 'energy boundary conditions'? -
Clouds provide negative feedback
RW1 - Sorry, looking at my last post I may have left some things unclear. Temperature averages will always, over the long term average, stay near the limits determined by the energy boundary conditions. Long term temperature averages change when those boundary conditions change. -
Tom Curtis at 13:06 PM on 19 April 2011CO2 lags temperature
novandilcosid #312, I have responded to your post, and having done so noted your matching post on the CO2 is saturated thread. -
Clouds provide negative feedback
RW1 - "OK, so then what is the mechanism controlling the energy balance? What is keeping the global average temperatures so tightly in check from year to year? From decade to decade? From century to century? Why don't we see much larger variation - like multiple degree C per year, per decade, per century? The climate system as a whole is remarkably stable." To put things briefly: Power radiated to space scales with T^4. This extremely powerful negative feedback keeps the temperature within the ranges you are discussing here. Unless the rate of energy input (insolation changes, large scale albedo from, say, ice changes) or output back to space (emissivity changes due to GHG's) change over an extended period of time (which tends to rule out clouds given their very fast response rate), temperatures will stay near the range determined by the energy boundary conditions. -
Tom Curtis at 13:03 PM on 19 April 2011CO2 effect is saturated
novandilcosid takes on basic physics on the CO2 lag thread. He writes:"1. The undisputed absorption figures for CO2 mean that an increase in concentration cannot directly greatly (I mean by more than 0.5W/m^2) increase the absorption of surface energy by the atmosphere."
novan calculates this by calculating the change in brightness temperature of the back radiation assuming the atmospheric temperature profile remains constant, and that the increased CO2 concentration reduces the average altitude from which the back radiation is emitted. The problem with this is not that it is in error, but what it ignores. Specifically, what heats the surface is not the back radiation but the sun. The way the back radiation effects the surface temperature is only by modulating the rate at which heat escapes, but it is a minor player in that role. Far more important is convection, which carries heat rapidly to the upper atmosphere. In the event that the upper troposphere warms, as for example, because of reduced IR radiation because of increased CO2 concentrations, that will slow the rate of convective heat transfer, and because heat is being carried away from the surface slower, the surface will warm until equilibrium is reestablished. This will result in an increase in back radiation, but because the lower atmosphere has warmed, not because of the lower effective altitude of emission of back radiation."4. All very well, but what about the rest of the CO2 band? At STP 50% of wavenumber 650 emissions are absorbed in the first 25m of atmosphere. At say 17km the same number of CO2 molecules occupy about 250m. The pressure decrease over these 250m means only a small narrowing of the emission/absorption lines, so absorption rate will not be greatly affected: at 17km just under half the wavenumber 650 photons are absorbed within 250m. 5. I calculate that the published absorption data for CO2 means that the great majority of emissions from CO2 must be coming from above the Tropopause."
It is odd that novan concentrates his discussion on the 650 wave number. It is well known that at that wave number, CO2 absorption is at its peak, and that as a result the majority of CO2 emissions to space at that wavenumber come from the stratosphere. However, the CO2 absorption band in the atmosphere is approximately 350 cm^-1 wide, with most of that band being much weaker absorption than at 650^-1. Science of Doom has calculated the change in transmission at the troposphere for a doubling of CO2:
This is total change in transmittance, and does not take into account the emissions by the CO2, but the effect of the stratosphere and above on transmittance or emissions in the wings (<625cm^-1, >715cm^-1) is negligible. The consequence of including all the line numbers in your calculations (rather than just one, and done by novan) is to show that increasing CO2 concentrations reduces total emissions to space from the upper troposphere, requiring a compensating warming of the surface to restore the energy balance.
Moderator Response: [DB] Closed blockquote tag. -
CO2 lags temperature
novandilcosid - This thread discusses the fact that CO2 has lagged temperature changes in the past, often used as a 'skeptic' argument that changing CO2 concentration now won't be a problem. The Milankovitch cycles driving the repeated glaciation of the Earth only supply a very small forcing (both up and down), not enough to change temperatures very much by themselves. They do induce CO2 feedbacks (vegetation changes, but primarily changes in solubility of CO2 in the oceans, which is inversely related to temperature); these act as positive feedback, amplifying the Milankovitch changes. The ocean CO2 feedback takes 500-1000 years due to deep circulation - hence the lag seen in the ice cores. Both also affect water vapor (more powerful a greenhouse gas than CO2), which takes a matter of weeks or so to respond. Further amplification occurs (in both directions) with changes in ice coverage and albedo. Once a swing in base forcing occurs, that change is greatly amplified. The total effect with feedback amplification (each feedback having it's own time frame) is to produce the temperature swings seen in the glacial cycle. --- Now we're inducing a very large and very fast temperature forcing by artificially increasing CO2 levels to amounts not seen since the Pliocene, when global temps were 2-3°C higher than today, global sea level 25 meters higher than now. This forcing is larger than the Milankovitch cycle changes. And that can't be good. -
novandilcosid at 12:46 PM on 19 April 2011CO2 effect is saturated
My take on the science is this: 1. The undisputed absorption figures for CO2 mean that an increase in concentration cannot directly greatly (I mean by more than 0.5W/m^2) increase the absorption of surface energy by the atmosphere. 2. The increased absorption of sunlight by the upper atmosphere means a drop in insolation at the Surface of about 1W/m^2. The increased back radiation due to the decreased average altitude of the CO2 surface-bound emissions is about 0.5W/m^2, so the NET direct effect of doubled CO2 on the Surface is a cooling forcing of 0.5W/m^2. 3. At the other boundary, it is clear from the outgoing spectra that CO2 is responsible for between 15 and 18W/m^2 of the emissions to space. It is also very clear that the emissions at the stronger wavenumber 670 are stronger than the rest of the CO2 band. Because emissions to space have to get through the overlying gas, it is also clear that the more strongly absorbed wavenumber 670 emissions are coming from higher in the atmosphere than say the wavenumber 650 emissions. So in this case, Higher = hotter, ie the wavenumber 670 emissions are definitely coming from the stratosphere. 4. All very well, but what about the rest of the CO2 band? At STP 50% of wavenumber 650 emissions are absorbed in the first 25m of atmosphere. At say 17km the same number of CO2 molecules occupy about 250m. The pressure decrease over these 250m means only a small narrowing of the emission/absorption lines, so absorption rate will not be greatly affected: at 17km just under half the wavenumber 650 photons are absorbed within 250m. 5. I calculate that the published absorption data for CO2 means that the great majority of emissions from CO2 must be coming from above the Tropopause. 6. If so, then we would expect a doubling of CO2 to have a COOLING effect on the planet. -
novandilcosid at 12:40 PM on 19 April 2011CO2 lags temperature
I thank the moderator, and apologise. The headline post makes the assertion that CO2 amplifies temperature. It is my view that the ice core data shown does not support that assertion. If temperature was being amplified proportionately to CO2 concentration then we would expect to see some influence of this on falling temperatures. I don't see this effect at all in the data. -
RW1 at 12:39 PM on 19 April 2011Clouds provide negative feedback
Sphaerica (RE: 27), "Yes, it is coincidental. That is, both are true, but neither mean anything." The AGW theory seems to require an awful lot of coincidences. "Yes it does, every time the seasons change. That is, the change in temperature in the temperate zones is greater than could be accounted for by the mere change in hours of insolation and angle of incidence of the sun (and change in albedo from winter snow to bare ground). Humidity also rises, and the GHG effect from this amplifies the temperature. This happens, any you experience it, every spring." I generally meant globally - not seasonal or more local temperature change. I'm well aware that seasonal change is due to significant hemispheric insolation change. "But to give your question a more direct answer, you seem to be describing a runaway. As long as the feedback is less than the original forcing, it is positive, but not a runaway. This is the simple case of a convergent versus a divergent series in mathematics." I'm not describing a runaway effect. "So if they had a moderating effect they would be a serious damper in the system. But they don't. And if they were, because they operate so quickly, you would see their effect instantly. Which is exactly why clouds cannot be a major factor. On the time scales over which clouds vary, if in fact they were a moderating influence, then the temperature of the earth would never, ever vary by more than a fraction of a degree (or the clouds would quickly step in and stop it)." But it generally does not vary by much at all. The global mean average temperature tracks very, very tightly - rarely is there a difference from year to year more than 2 or 3 tenths of degree. "Anything which operates on that fast a time scale is either the primary control, or it's not a control at all. All evidence points to "not at all." OK, so then what is the mechanism controlling the energy balance? What is keeping the global average temperatures so tightly in check from year to year? From decade to decade? From century to century? Why don't we see much larger variation - like multiple degree C per year, per decade, per century? The climate system as a whole is remarkably stable. "Which is exactly why clouds cannot be a major factor. On the time scales over which clouds vary, if in fact they were a moderating influence, then the temperature of the earth would never, ever vary by more than a fraction of a degree (or the clouds would quickly step in and stop it). You'd never have ice ages, Medieval Warm Periods, Little Ice Ages, or any notable variations. And yet over the history of the earth the temperature has varied by as much as 10˚C" Most of these changes, except the MVP and LIA, are much longer term and driven by very large external forces - not relatively small internal forcings. External influences aside, just topographical differences alone due to plate tectonics had a huge impact on surface albedo over the Earth's history, which in turn had a huge influence on temperature and climate. The ice ages and interglacials are driven by changes in the Earth's orbit, etc. "It may be a slightly positive or slightly negative feedback, but it's not a control, and not even a major feedback (compared to H2O, CO2, and albedo)." I don't know how you can say this. A very large amount (if not most) of the enhanced warming from the climate models comes from positive cloud feedback. "Look here for further information on how we know that climate sensitivity is not low, so any moderating influence of clouds cannot be a major, fast acting factor. 'For example, between glacial and interglacial periods, the planet's average temperature changes on the order of 6°C (more like 8-10°C in the Antarctic). If the climate sensitivity is low, for example due to increasing low-lying cloud cover reflecting more sunlight as a response to global warming, then how can these large past climate changes be explained?'" Very simply. The large change and increase the distribution of the Sun's energy in the northern hemisphere combined with a positive surface albedo feedback is enough to overcome the negative cloud feedback. -
ranyl at 11:22 AM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
As CO2 rises and the world warms, weather patterns change (dry to wet and wet to dry) geographically as the tropics widen and in essential character as drought and deluge becomes the way of the weather. There will be winners and losers in the eco-systems present, as exampled by this years Amazon drought and (in some areas) drought breaking rains in Austrialia. Yet overall it appears the sinks are shrinking and going to shrink further. "Their efficiency in removing CO2 emissions from the atmosphere is expected to decrease in the future under increasing atmospheric CO2 because of their response to elevated CO2 levels, warming and other climate changes. Recent evidence from observations and models suggests that the efficiency of the sinks could have already decreased in the past few decades, but the uncertainties are very large" Trends in the land and ocean carbon uptake Corinne Le Que´ re´ 1,2 Current Opinion in Environmental Sustainability 2010, 2:219–224 Also keep in mind that all the models used to estimate safe CO2 emissions and future carbon cycle behaviour don't include permafrost release and keep increasing the sinks. Then add in ocean warming, rain_forrest droughts, ozone effects, pest increases, the nitrogen situation (reactive nitrogen additions to the land have been a net negative radiative forcing for the 50 years and have significanlty increase primary production), etc...etc Then consider that the Pliocene was 3-5C (1.8-3C in a hundred years of 350ppm or 2090) than present on 350ppm and we're at 390ppm. Stop all emissions today and the gradual uptake by the sinks (~100-200years) will remove another 10-20% of the 110ppm addition of Co2 there has been, so taking it down to an equilibrium of ~370ppm a level at which it will then stay at for eons. Of course as always it is slightly more complicated for as the atmospheric CO2 falls the sinks re-release the carbon they stored, meaning we don't get away with that easy and will still have take all the CO2 out of the atmosphere to get to 350ppm (40ppm or 20 years of current emissions). Then add in the 7-14ppm release per 1C that occurs as the world warms and massive losses to biodiversity that are occuring due to other human past times (meaning eco-systems are unhealthy and vulnerable) making biosphere carbon release much more likely. So the reality is to get anywhere near 2C, and not be facing traumatic change, there is a need to at get least 40ppm of CO2 out the atmosphere as of now, i.e. forget having a carbon budget the human race already has a huge carbon debt and every ounce of carbon from now on just adds more to it. Prevention is better and cure and more effective the earlier it is done so means stopping all fossil carbon emissions asap and transforming land use such that, it not only becomes an enhanced carbon sink but also provides sustainable food, fuel and materials. Even with all that the temperature rise is still likely to rise to at least to 1.5C so major adaptations are already necessary and they will have a carbon cost. Everything that needs fossil fuels to exist (e.g. wind turbines) are extra carbon costs, and as to have any chance of reachign 350ppm all FF emissions really have to stop asap so payback Fossil carbon displacement is a false accounting. Considering basically everything is totally fossil fuels dependent at present and to date CO2 emissions just keep going up (yes 2009 dipped but 2010 rose to the challenge again) both suggestive that all actions so far have been futile; Does anyone have any suggestions?Moderator Response: Converted to hyperlink -
Marcus at 11:19 AM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
Might I also suggest, John D, that you stop misrepresenting what I said before. I clearly said they did *little* to simulate future conditions-I did *not* say they did nothing at all to simulate it. In fact, as poor a simulation as I believe this to be, it went further than any of the other FACE trials I looked at-which seem to look strictly at eCO2 alone. Again, all the yield boosts you mentioned came from the more ideal conditions + eCO2, yet still the message they present is grim-with future soil-borne disease issues, acclimation issues, poor nitrogen use efficiency & predicted drops in yields across the majority of Victoria between now & 2070. Of course, being in denial, you've chosen to focus only on the numbers which you think "prove" your case. -
Marcus at 11:05 AM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
"Why then are you now claiming they did little to simulate expected changes in temperature and precipitation when it so clearly was a integral part of the trials" Yes I recall the study, & I remember thinking at the time that it was a pretty poor recreation of the kind of conditions that we expect to see in 20-40 years time. You've clearly forgotten that. You've also clearly forgotten that the yield increases you cited were *only* seen under the more ideal conditions (regular sowing times & under irrigated agriculture). Likewise you forgot how they mentioned that they were already seeing the impacts of acclimation after just 3 years. Lastly, you seem to forget that the leader of the project was incredibly downbeat about the results in the summary he presented at the time. I think you should make a better effort to understand the FACE trial, & its implications, yourself before you accuse me of a lack of understanding. -
scaddenp at 10:31 AM on 19 April 2011Christy Crock #4: Do the observations match the models?
rhjames - a perfectly valid model result can give you 15-20 years of little warming. Look at Keenlyside & Motif fuss for an example. Each model run is an instance of a possible climate. No way at moment to know which one we will get. The grey area is boundary of all model runs in the example. The actual should lie in there. More on this at realclimate. Note particularly their graphic with the many model runs on it. -
LukeW at 09:55 AM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
Villabo - you remain unread as to how major droughts break in Australia, decadal influences, and the importance of major floods in recharging rivers and groundwater. Sorry but it's our underlying lot in life and our natural ecology (exclude Europeans) is adapted to it. Las Ninas are not evenly spread either. So good luck finding a climate change signal in there with the current time series ! Sorry to harp on off-topic. But more to the point extrapolating from CO2 fertilsation to other AGW doom and gloom issues is also off topic. As for CO2 - all I have said is that the jury is still out and things are quite complex. FACE experiments are indeed equivocal and not as good as laboratory studies. As for declines in quality of foodstuffs - well let the plant breeders work at it. You'll be surprised. Don't assume that the current varieties are all you'll have in the future. Same would have been said 100 years ago. I would be more concerned about natural systems - unknown interactions of C3 woodies overtaking C4s by basic metabolic efficiency. Impact of frost from CO2 sensitivity on natural species. But some nation states may win out of AGW on crops and extra CO2. It's Liebig's law of the Minimum. In general I think extra rainfall and temperature will help C3 crops. The way things are going - hope you're one of those nation states. There won't be a global deal on CO2 mitigation and adapation is where we're at. Time to prepare. -
johnd at 09:30 AM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
Marcus at 09:20 AM, we've discussed the Horsham FACE trials in depth some time back in another thread, and you claimed to have studied and understood the results. Why then are you now claiming they did little to simulate expected changes in temperature and precipitation when it so clearly was a integral part of the trials? Do you recall that, or didn't the results make it clear enough for you? -
Marcus at 09:28 AM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
That map in the Horsham FACE trial is also nothing to be optimistic about. Almost the entire map shows areas with declining yields between now & 2050-with some areas only expected to decline by 2070, & only a few smatterings of areas that expect to see a yield increase between now & 2070. Again, what the people running the FACE trial are telling us is *very* different from what John D is trying to sell it as. -
novandilcosid at 09:27 AM on 19 April 2011CO2 lags temperature
CBDunkerson wrote: "That CO2 causes higher surface temperatures (aka 'the greenhouse effect') was first proven by John Tyndall more than 150 years ago. Articles explaining how this works and correcting other fundamental errors in your analysis above can be found on this site at; Has the greenhouse effect been falsified? and The greenhouse effect and the 2nd law of thermodynamics" I thank CBD for his response to my post. I would be grateful if he would identify all the "fundamental errors" in my post rather than referring me to vague and unspecific articles. My main ponts are: 1. The undisputed absorption figures for CO2 mean that an increase in concentration cannot directly greatly (I mean by more than 0.5W/m^2) increase the absorption of surface energy by the atmosphere. 2. The increased absorption of sunlight by the upper atmosphere means a drop in insolation at the Surface of about 1W/m^2. The increased back radiation due to the decreased average altitude of the CO2 surface-bound emissions is about 0.5W/m^2, so the NET direct effect of doubled CO2 on the Surface is a cooling forcing of 0.5W/m^2. 3. At the other boundary, it is clear from the outgoing spectra that CO2 is responsible for between 15 and 18W/m^2 of the emissions to space. It is also very clear that the emissions at the stronger wavenumber 670 are stronger than the rest of the CO2 band. Because emissions to space have to get through the overlying gas, it is also clear that the more strongly absorbed wavenumber 670 emissions are coming from higher in the atmosphere than say the wavenumber 650 emissions. So in this case, Higher = hotter, ie the wavenumber 670 emissions are definitely coming from the stratosphere. 4. All very well, but what about the rest of the CO2 band? At STP 50% of wavenumber 650 emissions are absorbed in the first 25m of atmosphere. At say 17km the same number of CO2 molecules occupy about 250m. The pressure decrease over these 250m means only a small narrowing of the emission/absorption lines, so absorption rate will not be greatly affected: at 17km just under half the wavenumber 650 photons are absorbed within 250m. 5. I calculate that the published absorption data for CO2 means that the great majority of emissions from CO2 must be coming from above the Tropopause.Moderator Response: Your comments regarding the physics of the greenhouse effect are off-topic for this thread and are covered elsewhere. Per this site's Comment Policy, please review the appropriate posts and place your comments there. In addition to the links provided by CBD you may find the CO2 effect is saturated thread relevant. Future off-topic comments will be removed. -
Ed Davies at 09:23 AM on 19 April 2011Christy Crock #4: Do the observations match the models?
This Standford video of a Ben Santer talk is a very illuminating introduction to the problems with the Douglass paper. Thanks to whoever referenced it originally - I'm fairly sure it was in a comment on this blog. -
Marcus at 09:20 AM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
Back to the issue at hand-in spite of all the hand-waving & obfuscation being done by John D, BP & Luke, the fact remains that attempts to claim that enriched CO2 will be beneficial for agriculture are overly simplistic-as they ignore all the other negative impacts that might well result from either enriched CO2 directly, or from changes in hydrology & temperature that will result. These facts are backed up even by the results of the FACE trials in which they place so much faith-even though said trials do little to simulate expected changes in temperature & hydrology. Drops in nutrition, resistance to insect pests & increased soil-borne pathogens have all been shown to occur under eCO2 *alone*-which will almost certainly have a negative impact on crop yields & increase the cost of cropping for farmers. Certainly, just the known dangers to agriculture posed by increasing CO2 emissions should be sufficient to make us want to pursue a more prudent approach to the burning of fossil fuels. In Denial World, however, the risks are entirely worth it if it means a continued reliance on fossil fuels. -
rhjames at 09:20 AM on 19 April 2011Christy Crock #4: Do the observations match the models?
I have to agree with Gilles - even if the temperature had trended strongly downward over the past 15 years, it would still be within the grey area. If I simply look at the trend over the past 15 years, it certainly looks flat, rather then increasing. If I further consider the first quarter of this year thrown in, it further supports a flat trend. GISS is so far removed from all other data this year, that it's hard to take it seriously. However, let's leave it in as a source of data. If I look at the IPCC prediction, the direction is stongly upwards. However, if I blank out the gray area, and just look at the three data sets over the past 15 years (about the time the IPCC as predicted future data), I don't see a convincing upward trend. Therefore, I have to say that, at this stage, the actual data doesn't support the IPCC model trend in recent years. -
johnd at 09:12 AM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
JMurphy at 08:34 AM, once again you've overlooked the obvious. It is a University of Melbourne project, coincidently it was they who provided the FACE PowerPoint presentation I referenced earlier. Given the objective is to collect data that is beyond that contained in the official BOM records, BOM will be more of a beneficary rather than a contributor. -
Waste heat vs greenhouse warming
RSVP - Re: my rhetorical question about cherry-picking from the middle of publications: "For the same reason you didnt answer the question about the social security analogy?" I didn't answer your social security analogy because it's a horrible analogy, one that doesn't map to the climate system. Sunlight puts energy into the climate, adding to the surface air temperature (SAT) and ocean heat content (OHC), which then radiate increased IR to space. Waste heat also does the same, but at a level only 1% that of sunlight. It's not measurable as a climate effect until it shows up in the OHC and SAT, at which point the same temperature^4 radiation feedback applies to both. You're still treating waste heat as a separate pool of energy that somehow doesn't affect surface radiation (which it could only do if it didn't affect surface temperatures!), which is quite an unjustified and unphysical position to hold. -
Albatross at 08:34 AM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
Luke, John and Villabolo, If I may be so bold--could we please move the discussion back to the topic at hand? Arguing about what ifs and the IOD and ENSO (yes, I was guilty of that earlier too) is not helpful. -
JMurphy at 08:34 AM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
johnd wrote : "If you are not already aware of it these addresses should lead you to information about it. http://www.australiangeographic.com.au/journal/first-fleet-logs-reveal-climate-patterns.htm http://climatehistory.com.au/2010/12/02/volunteers-dig-up-tales-of-wild-weather-and-insect-plagues/" This is pure gold, as far as so-called skepticism is concerned. Any project involving the BOM and Met Office (two of the organisation most hateful to the so-called skeptics - due to their important leadership in that all-encompassing conspiracy, apparently), has a built-in rejection clause when the results are not as desirable as required for continuing obfuscation, i.e. "It was always going to be biased, fraudulent and untrustworthy - the BOM and Met Office are involved !" -
johnd at 07:52 AM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
villabolo at 07:34 AM, the flooding event you are referring to was not due to the La Nina alone, but rather to the combination of La Nina and a negative IOD. That combination merely replicated the conditions last bought in 1975, but also to some extent in 1942, 1933, 1917, 1916,1909,1906, and yet to be established prior to that. The difference now is that the ENSO and IOD are very close to being able to be accurately forecast 2 years out, and as has been happening, those who follow such forecasts are able to plan ahead with more confidence than those who don't, and so not everyone got caught out. -
johnd at 07:38 AM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
LukeW at 05:33 AM, good to see someone with their feet firmly on the ground and enough nouse to know whether it is dry or wet. There is a project that is collecting all available anecdotal evidence from journals etc to reconstruct as best possible, the early climate of Australia prior to the official record period. If you are not already aware of it these addresses should lead you to information about it. http://www.australiangeographic.com.au/journal/first-fleet-logs-reveal-climate-patterns.htm http://climatehistory.com.au/2010/12/02/volunteers-dig-up-tales-of-wild-weather-and-insect-plagues/ -
villabolo at 07:34 AM on 19 April 2011More Carbon Dioxide is not necessarily good for plants.
@100 LukeW: ""And you want those La Ninas to get stronger?" YES PLEASE !! Would make us billions ! (with some collateral damage too but life wasn't meant to be easy)" (Emphasis mine) Luke; concerning your response at #141 to my post #115. I am very well aware of Australia's variable climate throughout history. You are assuming my ignorance, in what I believe is an attempt to dodge my basic premise. As you yourself stated, La Ninas will become stronger and more frequent. I was simply stating that there will be more devastation than blessing as a result. An obvious example is what you saw happen to your wheat crop last season. That you admitted that production in Australia is problematic runs against the grain of your original statement in #100. You were describing the heightened effects of La Nina as if it were a cornucopia while grossly downplaying the destructive side. Recent events and rational intuition should give you an idea of what you country's future really has in store. More severely fluctuating weather than before, with more drastic effects than before. By the way, you can try out this thinking experiment: All percentages are based a previous average. Year 1: 130% bumper crop. Year 2: 50% crop devastation. Year 3: 70% harvest; 10% complete crop loss; 20% crop dwngraded to animal feed status. Question. What is the average harvest of crop fit for human consumption?
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