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Steve L at 02:24 AM on 14 October 2009How do we know CO2 is causing warming?
TP100, read more carefully. See comment #13 on this thread -- CO2 is not thought to be the only thing affecting climate. Nobody is claiming a runaway (runaways require positive feedbacks, but not all positive feedbacks yield runaways). Is there another forcing that has increased by 33% since 1750? Is there another forcing that might double over the next 100 years? Will solar forcing do that? But we can limit the amount of future forcing from CO2. That's not to say that we will "control" climate; rather it means that we can reduce the amount of anthropogenic forcing. I hope this gives you a clue as to why people tend to talk about carbon dioxide. -
shawnhet at 02:22 AM on 14 October 2009How we know global warming is still happening
WeatherRusty, I'm not sure what our disagreement is(if any) anymore. Your link appears to agree with my POV that higher levels of specific humidity are associated with higher(sustained) levels of precipitation. For instance"(1) No amount of rising air will produce precipitation unless moisture is present. The more **moisture that is present, the higher the potential for precipitation if uplift mechanisms are in place**." If atmospheric instability and uplift remain constant and the amount of specific humidity rises, we should expect more cloud formation. Cheers, :) -
chris at 02:14 AM on 14 October 2009How do we know CO2 is causing warming?
re #54 A couple of your points: We don't dismiss the effects of solar variation (there has been negligible secular solar variation since the late 50's and so this has made a negligibile contribution to the very marked warming of this period; it's estimated by solar scientists that solar effects may have contributed around 0.1 oC of warming to the 20th century trend).. J. L. Lean and D. H. Rind (2008) How natural and anthropogenic influences alter global and regional surface temperatures: 1889 to 2006 Geophys. Res. Lett, 35, L18701 http://pubs.giss.nasa.gov/abstracts/2008/Lean_Rind.html ...or PDO (a recent analysis of ocean current effects indicates that these have modulated the warming during the 20th century but have made almost zero net contribution)... K. L. Swanson, G. Sugihara, and A. A. Tsonis (2009)Long-term natural variability and 20th century climate change. Proc. Natl. Acad. Sci. USA 106, 16120-16123 www.pnas.org/content/106/38/16120.abstract ...or orbital changes (these have obviously played a major role in ice age cyles, and have had a small contribution to Holocene temperature variations, but their contrbution to the warming of the 20th century has been essentially zero)... ..or magnetic field effects (these have been studied in detail and there is no evidence that these have made an impact to warming of the last 100 years). So we certainly don't dismiss these things (or any factors that are known to affect climate). e.g. see Figure 2 here: http://www.skepticalscience.com/The-CO2-Temperature-correlation-over-the-20th-Century.html We didn't have "run away warming back in the Carboniferous period when Co2 levels were into the thousands of PPM as opposed to the 380 PPM today", because, in fact during the Carboniferous CO2 levels were generally very low (even possibly lower than today during parts of the Carboniferous and early-mid Permian). That's why the earth had some major long-lived glaciations and otherwise cold periods during the Carboniferous and early/mid Permian. During some parts of the Carboniferous when CO2 levels were a bit higher, the evidence indicates that the earth was warmer. In general there is a rather strong relationship between proxies for atmospheric CO2 concentrations and earth temperature regimes right throughout the last 500 million years. http://droyer.web.wesleyan.edu/PhanCO2(GCA).pdf -
TP100 at 01:59 AM on 14 October 2009How do we know CO2 is causing warming?
My apologies for posting twice. Tom Dayton - actually, I've read through the debate and I have found the AGW explanations lacking. The explanation essentially says - "we can't think of anything else that could cause the warming over the last 30 years, so it must be Co2". I am just not buying into that argument. There is a lot of information documenting that the earth is warming, and few people dispute those findings. The question is - is it really eing caused by man? While this website provides explanations, I can find equally if not better contrary explanations on skeptical websites. Re: my mythical questions - Is it a myth that Co2 is only .04% of the atmosphere? And, is it a myth that Co2 concentrations were much higher in prior geologic times? Is it a myth that Co2 is a relatively weak greenhouse gas? Is it a myth that Co2 is a nutrient to plants and would would not survie without it? My argument simply states that climate is massively complex, while when you boil down AGW theory to it's most basic level, it says climate is actually quite simple - if humans can control atmospheric Co2 levels, we can control climate. Nothing else matters, and that is an absurd argument. If that is an incorrect characterization of AGW theory, then why all the fuss about capping Co2 emmisions?Response: The argument "we can't think of anything else so it must be Co2" is indeed inadequate. But that's not the argument being made. On the contrary, posted above is empirical evidence that increased CO2 has caused an enhanced greenhouse effect. Theory says more CO2 will trap more heat leading to global warming. Now we have observations that quantitatively confirm this.
Is it a myth that CO2 is a relatively weak greenhouse gas? Yes, the empirical evidence confirms the amount of extra heat trapped by CO2. The numbers have spoken. Climate is certainly complex but the principle that CO2 traps heat - and that more heat in our climate leads to warmer temperatures - is straightforward.
Anyway, this is the second time I've clarified that CO2 is not the only radiative forcing but it is the most significant source of warming. If you continue to persist with the strawman argument that we're claiming "nothing else matters", those comments will be deleted. -
Alexandre at 01:41 AM on 14 October 2009Comparing CO2 emissions to CO2 levels
John, Good post, as usual. I have a somewhat off-topic quiestion, though. Mauna Loa and the Law Dome Ice core seem to match nicely. There´s a "skeptical" claim about ice cores not being accurate samples of the atmosphere over long periods of time. Ernst Beck says that. I think Jaworowski too. Do you have any comments or known papers about that? -
Tom Dayton at 01:03 AM on 14 October 2009How do we know CO2 is causing warming?
Sorry, TP100, everything you wrote is a myth. You're on the right web site to get answers. Look at the top left of this page and click "View All Arguments." But from the phrasing of your post, I think you would still be frustrated by such a point by point approach to getting answers. So I suggest that you first read cce's The Global Warming Debate, which will tie together the threads. Then come back to this site to look for answers to specific questions. -
TP100 at 00:24 AM on 14 October 2009How do we know CO2 is causing warming?
This discussion is quite interesting, but I have some basic observations that are pretty straightforward. First, just to state the obvious, no one disagrees that Co2 absorbs heat and helps keep the earth warm. However, the fundamental argumet of AGW theory is that this trace gas (at slighly less than .04% of the atmosphere) is THE key ingredient to controlling a massively complex system such as climate. We can essentially dismiss the effects of solar variation, PDO, orbital changes, magnetic field changes, or hundreds of other variables and their interrelationships because we know for a fact that Co2 is the single most important component and it's interrelationships with other variables such as water vapor completely dominate or overshadow all other forcings. The argument is absurd on it's face. Just reading through the posts from both skeptics and proponents provides a pretty good indication of the complexities surrounding this science. We hear that we are nearing a tipping point where we will have run away warming if we do not stop "polluting" our atmosphere with Co2. My quesion is - why didn't we have run away warming back in the Carboniferous period when Co2 levels were into the thousands of PPM as opposed to the 380 PPM today? Or for that matter in other subsequent periods when Co2 concentration was much higher than it is today? Instead, the earth went through several cooling and warming periods irrespective of the Co2 levels. Another observation that has been addressed to some degree in this discussion is that there is a diminishing return of warming caused by Co2, meaning that there is a non-linear relationship between Co2 levels and warming. Yet, what most models seem to show is a linear relationship that is not supported by the science. Lastly, if Co2 is so bad for our planet, why do people who own greenhouses increase Co2 levels to as much as 1000-1200 PPM? The reason is not because it causes harm, but because plants thrive in environments with higher Co2 levels.Response: CO2 is just one piece of the climate puzzle. However, as we're emitting so much CO2 into the atmosphere, it does happen to be a fairly large piece. We can theoretically calculate how much heat CO2 traps and taking into account all the various radiative forcings that cause warming, it is the greatest contributor:
We're not ignoring solar changes. We know the forcing from orbital changes and they're insignificant compared to the radiative forcing from CO2. The PDO has no long term effect on radiative imbalance - it's an internal variation resulting from the exchange of heat between the atmosphere and ocean.
You're right to point out that CO2 is not the only radiative forcing. It's important to keep this in mind when evaluating past periods where CO2 was higher than now. In some periods, the sun was less bright than now. In other periods, the planet had a completely different configuration with all the continents merged into a single continent so the radiation budget was much different.
Models and theory do not use a linear relationship between CO2 and global temperature - it's a logarithmic relationship. And our theoretical understanding is confirmed by empirical observations. As explained above, satellite measurements of outgoing longwave radiation and surface measurements of downward longwave radiation both find an enhanced greenhouse effect. Both are independent empirical confirmations of theoretical expectations. The way CO2 is behaving, the amount of heat it is trapping, has been quantitavely measured. -
Tony Noerpel at 23:02 PM on 13 October 2009Comparing CO2 emissions to CO2 levels
John Thanks for your effort. Small mistake, the atomic mass of carbon is 12 second paragraph. Does CO2 emission data include deforestation and cement manufacture? best regards TonyResponse: Thanks for spotting the typo - I used 12 in my calculations but mistyped it in my write-up. Yes, the emission data does include cement manufacture - see the CDIAC website for more details. Not sure that it includes deforestation though. -
ewe2 at 14:18 PM on 13 October 2009How do we know CO2 is causing warming?
#10 WAG, very perceptive post. I'm a non-scientist myself (I got as far as highschool chemistry), but this particular discussion has sparked an investigation into thermodynamics and even calculus(!). Thanks particularly to Tom Dayton, those are great resources! I'll add one here from the physics forum, it bears direct relevance. Some of the comments there are quite useful. Part of the problem with deniers is that they cannot grasp the interaction between macrolevel thermodynamics and microlevel thermodynamics, nor the relatively simple concept of equilibrium. -
ewe2 at 14:16 PM on 13 October 2009How do we know CO2 is causing warming?
#10 WAG, very perceptive post. I'm a non-scientist myself (I got as far as highschool chemistry), but this particular discussion has sparked an investigation into thermodynamics and even calculus(!). Thanks particularly to Tom Dayton, those are great resources! I'll add one here from the physics forum, it bearsRSVP at 06:24 AM on 13 October 2009How do we know CO2 is causing warming?
Referring to the link provided by Tom Daytons reply #46: As usual, an experiment that focussed on how easily CO2 can be heated with IR. This is not even close the experiment I described. In fact, it is just the opposite. The lack of sensitivity to detail here is not compatible with anything that resembles objectivity or honesty, which is a first requirement for any branch of science no matter how sophisticated or basic.Philippe Chantreau at 06:24 AM on 13 October 2009How do we know CO2 is causing warming?
Chris commented on this statement by Robbo: "Solar activity is declining over the next few hundred years." I'll indulge in my pedantic moment and point that it is even grammatically incorrect to use the present tense for something that will be happening in the future. Beyond pedantism, one could see a mindset revealed in the grammatical slip: that of taking one's wish as fact, even if that fact is not even in a temporal position to be verified. It's ironic that some, at the same time, complain about predictions made with a disclosed LOSU. After the pedant moment I'll have my "skeptic" moment too: What is the LOSU on the long term Sun's activity? If there isn't one clearly stated by an association of solar physicists, or if it's too high for my liking, I will call invalid any and all predictions on future solar activity. Just kidding, of course. That would be arguing in bad faith, as we well know.Philippe Chantreau at 06:09 AM on 13 October 2009How do we know CO2 is causing warming?
RSVP, there is no reply to the substance of your question because there is no substance. You are showing a rather profound ignorance of Physics and complaining because people here are pointing you to the big world out there where knowledge is to be found aplenty. All for the sake of bad rethoric. Now that's pathetic. John, would it be possible to cull all the politically charged non sense and stick to science? Adjective throwing with "hysterical", "liberal", "socialist" bulls**t like the "thought police" have no place in discussions of the science. And I dare say that I am not ready to give up the word "denier" when someone ignorant of science is denying science findings, or someone less ignorant is trying to call something green when it's red. This statement by Truth Seeker: "I have found the UN to be a horribly corrupt organization" is totally meaningless and bad rethoric, akin to a collective ad hominem. The same statement could draw from plenty of facts and be applied to the US government, or to military contractors, or to Boeing, or just about any organization/society in this world. How relevant is it?Philippe Chantreau at 05:28 AM on 13 October 2009Are humans too insignificant to affect global climate?
The methods used for attribution in the Nemani paper are still unclear to me. They seem to rely mostly on model calculated estimates for attributing NPP changes to CO2 "fertilization." I guess I am to assume that you now trust computer models integrating multiple variables, including biological elements with complex and not fully understood interactions. As for the statistics in their figure 4, I can only begin to imagine what kind of treatment would "skeptics" of the GW kind would give it. Of course, it would be out of bad faith, so I won't even go there. Furthermore, the largest increase is attributed to the Amazon rainforest being exposed to more sunlight. That seem to square with observations and models suggesting that the Amazon is and will be getting drier. This, however, is anything but good news if it continues throughout the century, as it could very negatively affect the carbon cycle, as analyzed in the Phillips et al (2009) paper. There is no shortage of papers showing how disturbances stemming from climate change would negate temporary gains from higher temps or CO2 "fertilization." This especially true at the higher lattitudes, whose forests have already been shown to be a lot less of a carbon sink than the tropical ones. http://www.sciencemag.org/cgi/content/abstract/323/5919/1344 http://rstb.royalsocietypublishing.org/content/363/1501/2259.abstract http://www.pnas.org/content/105/5/1551.abstract http://rstb.royalsocietypublishing.org/content/363/1498/1737.abstract So rejoicing at the Amazon'e NPP increase might be a little like enjoying the warmth and light of the fire starting to burn your house.Tom Dayton at 05:07 AM on 13 October 2009How do we know CO2 is causing warming?
Ah, but then that Physics Forums thread turns back to directly address RSVP's objections! A commenter there named BrianG sounds like a more articulate version of RSVP. The responses to BrianG describe the difference between thermal and infrared experimentation, labs for kids versus current professional science, and so on. But not until page 9, and seems like no further than page 9: http://www.physicsforums.com/showthread.php?t=312054&page=9Tom Dayton at 04:51 AM on 13 October 2009How do we know CO2 is causing warming?
Well, that Physics Forum thread deals with low-tech experiments only until about page 4, then goes off on other (but interesting!) directions. But here is one more experiment linked from that Physics Forums thread: http://www.picotech.com/experiments/global/globalwarming.htmlTom Dayton at 04:08 AM on 13 October 2009How do we know CO2 is causing warming?
Thanks for finding that video of the lab experiment, Steve L! I used that as a clue to find a worksheet for the students to set up that experiment. There's an excellent thread on Physics Forums, having links to more at-home and in-school experiments, plus explanations of how the science long ago moved on from such crude approximations: Need Help: Can You Model CO2 as a Greenhouse Gas.chris at 02:56 AM on 13 October 2009How do we know CO2 is causing warming?
Robbo #39 Your assertions are simply not in accord with real world evidenceWe are not likely to get a global surface temperature record anytime soon.
We've just had one. September 2009 was the warmest September on record: http://data.giss.nasa.gov/gistemp/tabledata/GLB.Ts.txt Now of course that's just one month. However Jun-Jul-August was the second warmest JJA on record. Of course that's just 4 months in a year. However it's rather telling that we're getting very warm surface temperatures during a period when the sun has dropped smack to the bottom of the solar cycle and is in a rather anomalous extended minimum.Solar activity is declining over the next few hundred years.
That's a totally unfounded assertion. It's not much better than the porky pies you tried to sell on that other thread. What evidence informs your view on that subject?Temperatures may start to rise at the 1976 to 1998 rate after the ‘interrupted warming’ in a decade or two
That doesn't make much sense Robbo, and it's an unsupported assertion. You cite Kennlyside and Latif further up the thread as some sort of justification of this notion. However Keenlyside and Latif predict a very large warming (0.5 oC) in the period around 2010 to 2030. N. S. Keenlyside, M. Latif, J. Jungclaus, L. Kornblueh & E. Roeckner (2008) Advancing decadal-scale climate prediction in the North Atlantic sector Nature 453, 84-88 (see Figure 4) You obviously have strong political views. But physics doesn't conform to one's political pursuasion (see King Canute and his "advisors"). If you have to make up stuff that simply isn't true and pretend that people show or say things that they don't actually say [***](Keenlyside, Latif, Trenberth and Fasullo) then there's something wrong with your politics..... http://www.skepticalscience.com/How-do-we-know-global-warming-is-still-happening.html (see posts #4 and #7)Steve L at 02:22 AM on 13 October 2009How do we know CO2 is causing warming?
I'm pretty disappointed that some people who don't really know how science works make complaints that responses to their ramblings include suggestions to actually read some science. I'm likewise disappointed that some people accuse those who accept the scientific consensus on AGW of being close-minded while all the time refusing to see what is presented to them. (If it helps: the null hypothesis can never be taken as truth because some other mechanism/phenomenon or combination of these may produce the same outcome; but for one theory to supplant another, it must explain/predict more than the incumbent theory. If you reject IPCC summaries, basic physics, accumulated knowledge and you insist that other readers stray from the topic of a post to indulge your pet notion, I submit to you that you are on the wrong website. You should be hanging out with others like you and blaming them for failing, after all these years, to incorporate your ideas and build a new quantitative understanding that challenges the predictive capacity of AGW theory.) That said, John may need a basic physics page where we can post links to simple experiments that readers can perform in their homes, or videos of simple experiments, that will help even his most kooky visitors to learn (despite their reluctance) without having to read. Let me start the ball rolling with this one: http://tinyurl.com/22gfv5 I also tried to find a video I've seen of looking through a tube with an infrared lens as a candle burned at the other side, and CO2 was sent into the tube. Unfortunately I couldn't find that video again. Sorry for straying from the topic, John, I'll try to do better next time.Tom Dayton at 01:37 AM on 13 October 2009How we know global warming is still happening
bit_pattern, the figure illustrates the change in heat content relative to 1950, not the absolute amount.bit_pattern at 23:48 PM on 12 October 2009How we know global warming is still happening
Regarding Fig. 1, what's the deal with it going to and below zero prior to 1950? It looks kind of as if it is trying to show that there was zero total heat content prior to 1950. Obviously I'm missing something here, can anyone explain?Riccardo at 20:49 PM on 12 October 2009How do we know CO2 is causing warming?
I see a lot of questions on basic physics or science altogether. Were we a group of people talking about everything drinking beer it could be ok. But here we're trying to talk about science and at least basic physics should be taken for granted. What sense should have complain about the "missing" of data on a self-invented very basic (and rather crude) experiment on heat transfer? And how about claming that because no one can _exaclty_ predict future warming the theory is invalidated or at best doubtful? Should we distrust Big Bang Theory because we don't even know if the universe will keep expanding or will collapse back? Or should we discard plate tectonics because no one can predict how high the Himalayan mountains will get? And, by the way, absorbtion by CO2, alone or in the atmosphere, is really well known both experimentally and theoretically and with great accuracy ... Did all those people claiming that human emissions cannot be enough to increase CO2 concentration ever tried to use basic gas physics to quantify it? Or did people claiming that 0.04% of CO2 can not do much harm ever compared the so called orbital forcing that pushes the planet in and out glacial ages with anthropogenic CO2 forcing? Oh yes, the feedbacks, but apart for a few cases (yet to be demonstrated and/or quantified) they do their job whatever the forcing is. So please, discuss the topic using the physics we all know and try to avoid emotional thinking. P.S. Back to physics, i'll try to answer to the first question in TruthSeeker #36. The different absorption bands reflect different so called vibration modes. Any molecule with more than two atoms may vibrate in several different ways. The probability of interaction between a photon and the molecule depends on the vibration that is going to be excited; hence the absorption is different for the different frequencies. It's a very general behaviour. You may roughly look at the variation of the dipole moment upon vibration to get an idea of the strength of the absorption for a given mode; the details are purely quantum mechanical in nature.RSVP at 18:04 PM on 12 October 2009How do we know CO2 is causing warming?
Tom Dayton: "RSVP, are you really unwilling to believe that some high school science teacher somewhere in the world could have beaten you to the idea of simulating the Earth's surface with a hot object and the Earth's atmosphere with a closed glass container? Or is the use of a thermometer the part of your proposed experiment that you think is uniquely original to you?" I think you could impress a lot of people by showing that a hot coin takes longer to cool by exhaling a few times into the atmosphere that surrounds it, because I doubt if anyone believes this. But if you know about this, please show me the data. You scoff at the proposal because the only physics you are concerned with is how CO2s energy can be raised by a portion of the IR spectrum, (CO2 that makes up only .04% of the Earths atmosphere).WeatherRusty at 15:03 PM on 12 October 2009How we know global warming is still happening
shawnhet, Convective cloud formation is a function of humidity, atmospheric instability and uplift. In short, humid air must be forced to rise and continue to rise and cool under unstable atmospheric conditions. These conditions reach to high altitude in the tropics because the warm, expanded troposphere extends to greater height allowing convection to reach to 50-60 thousand feet before encountering the capping stability of the stratosphere. This is all about buoyancy and laps rate, the actual temperature doesn't matter much, other than warm air can support a greater water content or mixing ratio and and thus more energy in the form of latent heat. You can learn a lot from the following cite: http://www.theweatherprediction.com/habyhints/114/WeatherRusty at 13:38 PM on 12 October 2009How do we know CO2 is causing warming?
"if it was a fact they could make better predictions of temperature." What I have never been able to understand is these claims of a lack of predictive skill. What predictions? Forget about the various modeled scenarios for a moment and concentrate on the basic expectation for 1.5C-4.5C of temperature increase due to a doubling of CO2 with something close to 3C as most likely. This value of climate sensitivity is for the system at equilibrium with the radiative forcing. CO2 has increased by less than 40% since the industrial revolution and temperature has increased by about 0.7C. If the current radiative imbalance of 0.85W/m^2 were at equilibrium, about another 0.6C would be realized getting us to ~1.3C. Correct me if I am wrong. At 40% CO2 increase and 0.7C realized with 0.6C in the pipeline it would appear we are close to on track for ~3C of warming from a full doubling of CO2.TruthSeeker at 11:17 AM on 12 October 2009How do we know CO2 is causing warming?
"There is a proper and seemly scientific scepticism. This has been replaced by arrogance and a very misplaced confidence in our level of scientific understanding. The problem of a lack of scientific scepticism is compounded by a liberal fringe who take catastrophic global warming as a article of faith" Well stated! Like I said, if it was a fact they could make better predictions of temperature.Response: Regarding global temperatures, keep in mind that the atmosphere is only one small part of the climate - around 95% of global warming goes into the oceans. Consequently, heat exchange between the ocean with its much greater heat capacity and the atmosphere can cause significant changes in surface temperature. This is why surface temperature is such a noisy signal.
Nevertheless, there is a long term warming trend to be found within the noisy signal. This trend is due to the enhanced greenhouse effect causing a radiative imbalance meaning the planet is accumulating heat. This radiative imbalance has been confirmed by many empirical measurements - satellite measurements of outgoing longwave radiation, the accumulation of ocean heat content, surface measurements of downward longwave radiation and satellite measurements showing more energy coming in than escaping back out to space.TruthSeeker at 10:55 AM on 12 October 2009How we know global warming is happening, Part 2
I really don't understand what this heat content thing proves. The fact of the matter is that the AGW argument has ben propagated by the correlation between CO2 and temperature, not heat content (so are you now changing the definition?) Also, you would expect the heat content is a lagging indicator of energy induced. So even if the current leveling off of temperature reflects a reduction in the cause of global warming, you wouldn't pick it up in the heat content until you got to levels where it created a cooling environment.Response: This "heat content thing" proves that the planet is in energy imbalance. That the planet is accumulating heat. And as we've seen elsewhere, the imbalance is caused by an enhanced greenhouse effect in turn caused by increasing CO2 (and to a lesser effect, CH4).
Our climate system is governed by a relatively simple principle: when the planet is in energy imbalance, global temperatures change. Eg - when you add heat to the system, it warms. How much the global temperature changes is determined by climate sensitivity.
Of course, even while the planet is accumulating heat, it's possible for the surface temperatures to show short term cooling trends due to the exchange of heat between ocean and atmosphere. For example, over the last few years, we've transitioned from El Nino conditions to La Nina conditions which has had a slight cooling effect on surface temperatures.
This internal variation is like a noisy signal imposed upon the long term warming signal. But some have interpreted several years of cooling as a sign that global warming has stopped and we've now entered a long term cooling period. By noting that the planet is still in energy imbalance, we are reminded that global warming is still happening.
Re heat content lagging energy induced, satellite measurements of energy in and out give us a relatively instantaneous picture of the planet's energy imbalance - they also find more energy coming in than escaping back out to space.Robbo the Yobbo at 10:50 AM on 12 October 2009How do we know CO2 is causing warming?
There is a table in AR4 showing various climate forcings. It has a column describing the Level of Scientific Understanding - LOSU. Very little is understood with much certainty about climate. Yet this translates into the debate is over or the truth is out there for those willing to see it or, sometimes, that 'deniers' should be taken off to re-education camps. Give me a break. My background is as a hydrologist. In the normal course of events I wouldn't give a professional rat’s arse about climate. What I have been wondering about for 20 years is why we get 20 to 30 years of ‘drought dominated regimes’ followed by 20 to 30 years of ‘flood dominated regimes’. The answer lies in the Pacific Ocean of course. There appear to be ocean climate cycles with a low frequency modulation remarkably similar to Hale Cycle solar periodicity. There are thousands of papers on this in the hydrological and oceanographic literature. Yet it has been almost entirely missed by the IPCC – with only the barest mention of the Pacific Decadal Oscillation – one small aspect of the phenomenon. As a result of the low frequency ocean state modulation – I hypothesised back in 2002 that there would be a cooling influence likely to be experienced for 20 to 30 years. This was a big call in 2002 – so I thought about it for 3 days non-stop and finally rang Australia’s leading hydro-climatologist who said I was right and not insane. I could wish for more definitive ocean heat content data – but multiple strands of evidence show little if any evidence of current ocean and atmospheric warming. We are not likely to get a global surface temperature record anytime soon. This would depend on a conjunction of high solar activity in the 11 year Schwarbe Cycle with a strong El Niño. Solar activity is declining over the next few hundred years. A strong El Niño is very unlikely in a cool ocean mode. The best indication of a cool ocean mode is a negative PDO – although the PDO should be viewed as a climate signal rather than having any climate significance in its own right. A strong El Niño is very unlikely while there is a cool mode PDO. Temperatures may start to rise at the 1976 to 1998 rate after the ‘interrupted warming’ in a decade or two. Flimsy theory indeed. Google 'multi decadal ocean temperature variation' and you will get 124,000 hits. Google 'decadal ocean temperature variation' and you will get 635,000 hits. There is a proper and seemly scientific scepticism. This has been replaced by arrogance and a very misplaced confidence in our level of scientific understanding. The problem of a lack of scientific scepticism is compounded by a liberal fringe who take catastrophic global warming as a article of faith. The history of the human race shows a much greater proclivity for people to hysterically embrace prophecies of doom than to rationally resist the temptation to apocalyptic visions. Things are always much worse than we imagine and always on the brink of disaster. Reality seems to be that we are not going to hell in a hand basket (well - more than ordinarily) anytime soon. Not with the program? Oh my God.Response: Please point me towards these multiple strands of evidence for no ocean warming.
Also, please refrain from ad hominems of "liberal fringes" who "hysterically embrace prophecies of doom". The topic of this post was to determine whether there's empirical evidence for an enhanced greenhouse effect in the peer reviewed scientific literature. Pretty straightforward analysis - no faith, no liberal politics, no catastrophic prophecies of doom. Future comments that stray from science in such a manner will be deleted.TruthSeeker at 10:32 AM on 12 October 2009How do we know CO2 is causing warming?
Also, what is the significance of -2 deg brightness temperature? What was predicted, and how does this compare? What is the normal change we should expect to see? What is the degree of error in the instrumentation? Could this change have occurred due to different instruments taking the reading? Is it odd that all wave lengths went down?Tom Dayton at 10:28 AM on 12 October 2009How do we know CO2 is causing warming?
RSVP replied to John Cook: "Excuse me, but my experiment/query is not concerned with how much IR energy CO2 absorbs. The experiment is designed to demonstrate the impact CO2 may have on the TIME it takes for materials to cool. Your answer does not at all reflect your having understood the question nor its significance." (Oh, and s/he called me a liar.) RSVP, are you really unwilling to believe that some high school science teacher somewhere in the world could have beaten you to the idea of simulating the Earth's surface with a hot object and the Earth's atmosphere with a closed glass container? Or is the use of a thermometer the part of your proposed experiment that you think is uniquely original to you? And the many experiments that have not taken the form literally described by you, really are better. Apparently you do not understand the basic physics of temperature and radiation. Do you keep switched-off appliances plugged into all the electric outlets in your house to prevent the electricity from leaking out all over the floor? If not, I presume that is because you have a rudimentary understanding of electricity. You need a similarly rudimentary understanding of temperature, heat, and radiation. You could get that from reading, but you seem to have not actually read any of the material that John Cook and the folks commenting here have pointed you to.TruthSeeker at 10:02 AM on 12 October 2009How do we know CO2 is causing warming?
John, I really appreciate your site, and this post tying the concepts together is the first I have seen presented in a credible way. That being said, I also like many of the commentaries, for instance I think that Robbo The Yobbo has brought up many good questions that haven't been satisfactorily addressed. In addition to his, I have the following questions regarding this post: 1) RSVP asked "Kind of funny how you see a change around 600 cm-1, but no change around 1000 cm-1." And you responded " [ Response: Different bands react in different ways - observations match theoretical expectations in this case. ]" Please provide additional explanation, I don't know what your response really means. 2) Despite that you have made convincing arguments about AGW, the model predictions about future global temperatures based on CO2 remain horribly inaccurate. If it was truly as explainable as the presented arguments suggest, the predictive ability of the models would be good. How can science claim AGW as a fact without evidence that its impact on future climate could be predicted. 3) This is more of a statement, but I have found the UN to be a horribly corrupt organization and I find no more reason to trust their findings on this subject than in their ability to follow their own sanctions and laws.RSVP at 08:33 AM on 12 October 2009How do we know CO2 is causing warming?
To Greenhousegaseous: While there may be right wing conservatives resisting the idea that CO2 is causing global warming, that is not the real danger. The real danger is that we all decide that that is what is causing global warming, when in fact it isnt, or it turns out not to be. I am not more confortable believing the problem is not CO2, especially because I believe Global Warming is really happening. It is unfair to generalize about what the motives are for someone that is not with the program. And more power to us all if CO2 levels are reduced viewing excess CO2 as a pollutant. Wouldnt it be nice if it just turned out to be some natural phenomenon. I doubt this however, and find those with this flimsy theory as actually acting irresponsibly.RSVP at 08:08 AM on 12 October 2009How do we know CO2 is causing warming?
Philippe Chantreau said: "RSVP this stuff is so basic, it's textbook type of material. Scientists have known for 150 years. You obviously have done very little of your own research on this. Now you're accusing Tom to be lying, less he does it for you." Instead of a helpful reply, one that enthusiastically points to the data, I get two replies for the Thought Police. Not a single remark that even addresses the substance of what I have said. It is not my responsibility to proove your theories, and you should definitely not shirk when a question is asked. It is pathetic.RSVP at 07:55 AM on 12 October 2009How do we know CO2 is causing warming?
Response says: "On this page, there are 3 links to a list of all the papers on CO2 absorption properties (4 including this one)." Excuse me, but my experiment/query is not concerned with how much IR energy CO2 absorbs. The experiment is designed to demonstrate the impact CO2 may have on the TIME it takes for materials to cool. Your answer does not at all reflect your having understood the question nor its significance.Robbo the Yobbo at 07:33 AM on 12 October 2009How do we know CO2 is causing warming?
Including more data to 2000m? If it is real - heating should show up in the 700m profile as well as in the 2000m profile. It is highly unlikely that the 700m profile is not warming at the same time as the 2000m profile is warming. I wish Schuckmann et al had used total heat content rather than an undefined areal average - to make it comparable with other studies. A link to Susan Wijffell's presentation at last months Ocean Obs conference - see page 4 - none of the ocean heat content researchers agree with each other within the error bounds - but none are showing strong warming. Scuckmann seems to be an extreme outlier. I note that Dr Wijfells calculates ocean warming over 50 years at 0.3 W/m2 - whereas Schuckmann et al calculates recent (2003 to 2008) ocean warming at 0.77 W/m2. http://www.oceanobs09.net/plenary/files/Wijffels_HeatContentTemperature_2Aa_vfinal.pdf Schuckmann et al should be viewed with skepticism. I have provided a link to the latest evidence (based on the methods of Levitus et al) at the NODC. I think my point is not that the IPCC is political - but that it is a political stuffup.greenhousegaseous at 05:30 AM on 12 October 2009How do we know CO2 is causing warming?
Referencing the 2007 IPCC report isn’t useful in the scientific discussion. It was mainly a political document intended to get global political and business leadership off the dime on climate change. Those who assert that this *necessary* political aspect of the report means there was no scientific basis for the various predictions are naive: saying the IPCC was simply political isn’t a condemnation, only an observation. Indeed, in what at least some of us will see as a nice irony, the truly “political” nature of the IPCC report has now been revealed -- far from being “alarmist” predictions, the assessments of the science researchers involved were mostly watered down for fear of rightist political repercussions, in order to insure that the main governments would allow it to be published. In a delicious turn of the screw, we now know just two years later that the “alarmist” assessments of 2007 were dangerously conservative! Deviating from the primary scientific threads here is understandably tempting for those who cannot or will not understand the objective reality of AGW and aggravated climate changes. How much easier to accuse people of lying, to simply repeat already demolished untruths, to ignore well-demonstrated facts and trends that are inconvenient or discomforting, to deny that the data is plainly out there for all to understand and, if they have the data and rational goods, challenge. Hey, it’s a scary world we are busily creating, and there are quite legitimate reasons to fear it. An easy and all-too-human way to cope with such a looming catastrophe is to look for reasons to deny it. We should call these kinds of deniers doubters, IMO. Far from getting angry with them, we need to find better ways to inform them, as John himself observed a few posts back. http://www.skepticalscience.com/Some-Skeptical-Science-housekeeping.html Being an experienced publisher, I was struck by his thoughtfulness in stepping back to see how this blog interacts with its readers. It is an obvious publishing task that an amazing number of writers and bloggers never think to do. Kudos, John, as you kindly say to your commenters. But really, getting a much wider audience for these tough to handle topics is not your fundamental responsibility; you and most of the commenting posters here are doing a great job of exploring the science and its implications in terms many educated people can understand. Just please keep up this good and informative work; it is the foundation for the missing, but inevitable, much broader constituencyPhilippe Chantreau at 03:54 AM on 12 October 2009How do we know CO2 is causing warming?
RSVP this stuff is so basic, it's textbook type of material. Scientists have known for 150 years. You obviously have done very little of your own research on this. Now you're accusing Tom to be lying, less he does it for you.RSVP at 19:32 PM on 11 October 2009How do we know CO2 is causing warming?
Tom Dayton said: "RSVP, lab experiments of the type you describe (actually, much better designed than the one you described) have been done for more than 150 years. They are now done even in high school science classes." You are basically saying that it was a little boy who said that the Emperor was wearing no clothes. I knew that too, but was wondering if SOMEONE COULD DIRECT ME TO THIS DATA. AND something must definitely be wrong if we have been in the know for 150 years and not done anything about it. For this reason, I do not believe there is ounce of truth in your reply.Response: On this page, there are 3 links to a list of all the papers on CO2 absorption properties (4 including this one). There is indeed something wrong as we have known about the enhanced greenhouse effect for so long and yet so little has been done about it. That a website like Skeptical Science is even required, pointing out basic, empirically proven fundamentals like CO2 absorbing heat, shows how difficult it is to convince people of facts they do not wish to believe. Unfortunately, that's the psychological reality of cognitive dissonance.pekka.lehtikoski at 16:08 PM on 11 October 2009Human CO2 is a tiny % of CO2 emissions
This is a very good article, and it and comments answered to some of my questions. I hope you would post this content also in Wikipedia's [Carbon cycle] article, and link the article in wikipedia back to this page.Tom Dayton at 15:46 PM on 11 October 2009How do we know CO2 is causing warming?
RE: #24 RSVP and #25 my reply: Look in the green box immediately above this Comments section. There our host John Cook has supplied a link to an extensive collection of literature on the laboratory measurements of CO2 absorption properties.pekka.lehtikoski at 14:28 PM on 11 October 2009A broader view of sea level rise
Raising sea level seems almost a fact, and measurements appear good. But does this have any connection to global warming theory?Response: By "global warming theory", I assume you mean the notion that humans are causing global warming (also known as anthropogenic global warming or AGW). What does rising sea levels prove? It tells us that the planet is warming. We know this because the two major contributors to rising sea levels are thermal expansion (warming oceans) and melting land ice/glaciers.
Does rising sea levels prove that mankind is causing global warming? No. The reason we know we're causing global warming is because we're raising CO2 levels and CO2 traps heat which leads to the planet accumulating heat.pekka.lehtikoski at 13:32 PM on 11 October 2009Is Antarctic ice melting or growing?
The noise in ice mass data graphs compared to length of time period is poor. With this data the regression line can point to any direction, depending on selection of start end end dates, and calculated confidence in result will be 0. Besides I could find no significant correlation to NASA's temperature data. If you used better data, please include link. BR Pekka LehtikoskiRobbo the Yobbo at 13:11 PM on 11 October 2009How do we know CO2 is causing warming?
I will add a couple of additional sources that address decadal climate variation – by Dr Syun Akasofu and Professor Ole Humlum. http://wattsupwiththat.com/2009/03/20/dr-syun-akasofu-on-ipccs-forecast-accuracy/ - a reasonable summary http://www.iarc.uaf.edu/people/indiv/iarc_all_staff.php?photo=sakasofu - home page of Dr Akasofu http://www.climate4you.com/ - home page for Prof. Humlum The planet isn’t currently warming and the IPCC is a political stuff up rather than a credible scientific oganisation.JohnMashey at 13:10 PM on 11 October 2009How we know global warming is happening, Part 2
Nice article John, and the new website design is terrific. Thanks so much (and you should advertise, or if you did I missed it). All: see IPCC WG I, Section 5.2.2.3,Implications for Earth's Heat Balance, p.8 of the PDF, an especially Figure 5.4, which has a great chart that shows the heat takeup of various Earth elements, with error bars. Of course, there is newer data,but this is a great, an publicly-accessible summary, an that one chart eliminates a lot of silliness. Volcanoes aren't there, because undersea volcanoes are essentially irrelevant: they just don't produce enough heat to be interesting. Of course, big surface volcanoes cane relevant, but only when (like Pinataubo), they send enough sulfate aerosols high enough to cool the Earth. "Undersea volcanoes" are what I'd call M2 memes propagated by the usual blogs to confuse the unwwary. I.e., to see that they are wrong, you need to know just a little bit of climate science. (John: maybe it's worth augmenting your volcanoe discussion with a bit about undersea volcanoes, if you don't want to give that it's own item.Response: New website design? You haven't been here in a while, have you, John?
Are you sure that link to the IPCC report is correct? If you have links to data on undersea volcanoes, please do post them - would be much appreciated.Robbo the Yobbo at 12:14 PM on 11 October 2009How do we know CO2 is causing warming?
The essential question is not whether greenhouse gases are greenhouse gases – but to what extent they interact with myriad other factors to influence global climate. Ocean heat content has plateaued. The OHC page at the NODC shows the latest update. http://www.nodc.noaa.gov/OC5/3M_HEAT_CONTENT/index.html Schuckmann et al may indeed show a slight increase in OHC to 2000m – with everyone else showing slight cooling to slight warming to 700m. Talk about cherry picking. With a reduction in TSI since 2000 (http://www.pmodwrc.ch/pmod.php?topic=tsi/composite /SolarConstant) and a 1% increase in Earth albedo over the same period (http://www.bbso.njit.edu/Research/EarthShine/) – it would be very surprising if there were much warming going on. Schuckmann et al may need to revise their depth integrating or areal averaging algorithms. TSI will increase over the upward arm of the current 11 year cycle – but the longer term trend is downward. One should anticipate significant variability in ocean heat content – it is blindingly evident in the record of the recent past and ocean heat content must continue to be variable. Natural climate variability should be anticipated on 20 to 30 year – and longer - timescales. You continue to argue that natural variability is evident as an explanation for short term cooling – but continue to be non specific about what drives variability in the earth’s heat budget. I quote from NASA’s SORCE pages. ‘The Sun and Global Warming Of the many trends that appear to cause fluctuations in the Sun’s energy, those that last decades to centuries are the most likely to have a measurable impact on the Earth’s climate in the foreseeable future. Many researchers believe the steady rise in sunspots and faculae since the late seventeenth century may be responsible for as much as half of the 0.6 degrees of global warming over the last 110 years (IPCC, 2001). Since pre-industrial times, it’s thought that the Sun has given rise to a global heating similar to that caused by the increase of carbon dioxide in the atmosphere. If the past is any indication of things to come, solar cycles may play a role in future global warming.’ http://earthobservatory.nasa.gov/Features/SORCE/sorce_04.php Before you suggest that TSI peaked in 1958 – look at the TSI reconstructions in this report for AR4 from the British Met Office. Better yet - read the whole report. This should include the section on possible amplifying mechanisms for subtle solar variations. http://www.metoffice.gov.uk/publications/HCTN/HCTN_62.pdf It is very odd indeed you can insist on feedbacks for greenhouse gases – but want to ignore the feedbacks for solar variations. For example an increase in TSI and temperature leads to an increase in water vapour in the atmosphere. The same feedback as carbon dioxide – but with several others thrown in as well. While there is still considerable doubt on the exact values of TSI and TSI changes over time – the SST changes observed directly and as a result of interactions with global hydrology are reasonably conclusive. We are looking at natural variability producing a cooling influence for 20 to 30 years from 2000. The question of whether this is ‘warming interrupted’ – e.g. realclimate, Keenlyside, Swanson and Tsonis and Mojib Latiff – or something else entirely is not answerable at this time. However, from a number of lines of evidence – anthropogenic warming is at most 50% of what is claimed by global warming activists. Activists such as yourselves are continuing to promote alarmism. You need to develop a more nuanced understanding and a less dogmatic approach.Response: How is it cherry picking when you're including MORE data (down to 2000 metres as opposed to only down to 700 metres). As you say, with a reduction in solar activity since 2000, if the oceans are still retaining heat at a rate of 0.77 ± 0.11 Wm−2, there is obviously some other cause besides solar variations causing the energy imbalance. And considering we have satellite and surface measurements giving empirical confirmation of an amplified greenhouse effect, it's not surprising at all.
Regarding positive feedbacks, these apply to any sort of warming whether they be CO2 warming or solar warming. And there is always the possibility that there are other feedbacks unique to solar variations (eg - changes to ozone in the stratosphere, cosmic ray modulation of clouds). But if solar activity does have a greater effect on climate than generally thought, then what does that say about the current situation where oceans are showing a strong warming trend simultaneous to the sun cooling to it's lowest levels in a century?shawnhet at 09:37 AM on 11 October 2009Are humans too insignificant to affect global climate?
The paper referencing my above claim that the Earth has become 6% greener is Climate-Driven Increase in Global Terrestrial Net Primary Production from 1982-1999. Nemani et al. Also, above I made a typo above ... which have rather larger impacts on CO2 should read "...which have rather larger imapcts on plant growth". Cheers, :)shawnhet at 09:26 AM on 11 October 2009Are humans too insignificant to affect global climate?
Philippe, I would actually agree that CO2 is a minor factor compared to water and nutrients, but the point about constraints is that they matter **on the margins**. Imagine a plant could grow at speed S1 if it has N amounts of nutrients and W of water and C of CO2. The same plant, however, could grow at S2, if it had 2N, 2W and 2C, however, if it has 2N, 2W and 1C, it will only grow at speed S1. IAC, this point is moot, as a warming planet also has more water vapor in the air and more precipitation which have rather larger impacts on CO2. David Horton: If CO2 isn't good for plants, why do greenhouses pump it in? That one simple question will put all your silliness in context. People whose livelihood depend on growing plants quickly disagree with you about the benefits of CO2. Put simply, plants get carbon from the air and if the air has less carbon in it, a plant has to move a greater amount of air through its system to grow *when everything else is equal*. Calling something "denialist" doesn't address whether it is true. Also, your common sense idea that the Earth is getting less green is not science. I will try to find the reference that demonstrates how it is in error. Cheers, :)shawnhet at 09:10 AM on 11 October 2009How we know global warming is still happening
WeatherRusty, I'm confused. Don't you agree that condensing water is a primary constituent of clouds? Doesn't it follow then, that more condensing water makes it easier for clouds to become larger and thicker? Aren't the clouds in the tropics thicker and deeper than clouds in other parts of the world? OTOH, to require that there is positive cloud feedback requires that it becomes *harder* to condense sufficient moisture out of the air to form a cloud of size X as that air becomes more moist. Chris, THanks for the CLement paper, I'll take a look at it. Cheers, :)
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