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Comments 127401 to 127450:

  1. How 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=9
  2. How 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.html
  3. How 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.
  4. How do we know CO2 is causing warming?
    Robbo #39 Your assertions are simply not in accord with real world evidence
    We 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)
  5. How 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.
  6. How we know global warming is still happening
    bit_pattern, the figure illustrates the change in heat content relative to 1950, not the absolute amount.
  7. How 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?
  8. How 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.
  9. How 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).
  10. How 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/
  11. How 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.
  12. How 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.
  13. How 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.
  14. Robbo the Yobbo at 10:50 AM on 12 October 2009
    How 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.
  15. How 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?
  16. How 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.
  17. How 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.
  18. How 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.
  19. How 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.
  20. How 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.
  21. Robbo the Yobbo at 07:33 AM on 12 October 2009
    How 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.
  22. greenhousegaseous at 05:30 AM on 12 October 2009
    How 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 constituency
  23. Philippe Chantreau at 03:54 AM on 12 October 2009
    How 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.
  24. How 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.
  25. pekka.lehtikoski at 16:08 PM on 11 October 2009
    Human 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.
  26. How 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.
  27. pekka.lehtikoski at 14:28 PM on 11 October 2009
    A 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.
  28. pekka.lehtikoski at 13:32 PM on 11 October 2009
    Is 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 Lehtikoski
  29. Robbo the Yobbo at 13:11 PM on 11 October 2009
    How 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.
  30. How 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.
  31. Robbo the Yobbo at 12:14 PM on 11 October 2009
    How 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?
  32. Are 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, :)
  33. Are 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, :)
  34. How 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, :)
  35. Are humans too insignificant to affect global climate?
    Philippe, I commend your patience and politeness in dealing with the denialists on this blog. You are a better man than I. But the comment at #16 above could serve as a text book case of denialism in action. Mr Het believes the coal industry propaganda that CO2 is a "nutrient" and good for you. He plucks from somewhere, anywhere, who knows, perhaps just a figure made up by a denialist on another blog, the nonsense "6% increase in plant life on Earth over the last 20+ years". Who knows what this even purports to mean, as you pint out, but given the continued land clearing activities in Indonesia, the Amazon, Australia and elsewhere, common sense alone would tell you that "vegetation cover" of the planet is continuing to decrease. In addition we know that the effects of drought are both causing the loss of more vegetation and putting forests under stress so that they can absorb less CO2. Mr Het either knows none of this, or cares less, but he has wasted your time, and mine, and helped to fill up another thread with rubbish, hoping, no doubt that some other gullible person somewhere will pick up the "6%" pseudo data and run with it elsewhere. On John's next post our other resident denialists are up to the same tricks "water vapour" "CO2 saturation" "ocean absorption" "Nuclear tests(!)" and calls for "laboratory experiments". Again, they have no idea what these things mean, they are just random noise injected into a thread to try to stop the clear explanations of data provided by John being accepted by readers. Next thread they will be back again either with the same non-points or with other pieces of foolishness ("submarine volcanoes" "cosmic rays"). I am dealing with a plague of mice at present. I catch one, put it outside, catch another next day, put it outside, and on, and on. Doesn't matter how many mice I catch, they just seem to keep coming. Almost makes me think they have some way of multiplying faster than I can catch them. Just like denialists, except they have caused far more serious damage than a few mice..
  36. How we know global warming is still happening
    Re #58 Shawnet. The evidence supports the expectation from basic physics encapsulated in models that the atmosphere retains a roughly constant relative humidity as it warms [*] Also, the evidence indicates that a warming world doesn’t mean more clouds; in fact observational evidence from the Pacific indicates that cloud cover may decrease in a warming world. That’s the conclusion from a study just published in Science [**] [*] Dessler, A. E. et al. (2008), Water-vapor climate feedback inferred from climate fluctuations, 2003–2008 Geophys. Res. Lett., 35, L20704 Abstract: Between 2003 and 2008, the global-average surface temperature of the Earth varied by 0.6°C. We analyze here the response of tropospheric water vapor to these variations. Height-resolved measurements of specific humidity (q) and relative humidity (RH) are obtained from NASA's satellite-borne Atmospheric Infrared Sounder (AIRS). Over most of the troposphere, q increased with increasing global-average surface temperature, although some regions showed the opposite response. RH increased in some regions and decreased in others, with the global average remaining nearly constant at most altitudes. The water-vapor feedback implied by these observations is strongly positive, with an average magnitude of λ q = 2.04 W/m2/K, similar to that simulated by climate models. The magnitude is similar to that obtained if the atmosphere maintained constant RH everywhere. [**] A. C. Clement et al. (2009) Observational and Model Evidence for Positive Low-Level Cloud Feedback Science 325, 460 – 464. Abstract: Feedbacks involving low-level clouds remain a primary cause of uncertainty in global climate model projections. This issue was addressed by examining changes in low-level clouds over the Northeast Pacific in observations and climate models. Decadal fluctuations were identified in multiple, independent cloud data sets, and changes in cloud cover appeared to be linked to changes in both local temperature structure and large-scale circulation. This observational analysis further indicated that clouds act as a positive feedback in this region on decadal time scales. The observed relationships between cloud cover and regional meteorological conditions provide a more complete way of testing the realism of the cloud simulation in current-generation climate models. The only model that passed this test simulated a reduction in cloud cover over much of the Pacific when greenhouse gases were increased, providing modeling evidence for a positive low-level cloud feedback.
  37. How do we know CO2 is causing warming?
    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.
  38. How do we know CO2 is causing warming?
    I find Lorezo's remarks refreshing. It seems like a lot of money has been spent around testing the effects of CO2 on the Earth's atmosphere, but has anything like the following lab work been performed? That is, experimentation to show how CO2 actually impedes the COOLING of an object, and demonstrate that recycled heat is not getting around CO2 at other IR wavelenghts? In terms of a thought (or actual) experiment this might involve an elongated and sealed glass tube, (perhaps a few meters long) insulated thermically everywhere except on one end. At the base, inside the tube, a heating element would be used for heating a radiative plate wired with sensors that allow monitoring temperature over time. The opposite (non-insulated) tube ending would protrude into a cool dark chamber where the heat radiation is absorbed. For experiments, the tube would be filled with air having controlled amounts of CO2. The heating element would be switched on to leave the temperature of the plate at some specific elevated value. It would then be switched off to allow the plate to cool. The data of interest would be the TIME it takes for the plate to cool for the different levels of CO2. Indications that cooling actually take longer for higher levels of CO2 would be consistent with the idea that CO2 plays a significant role in global warming. If cooling times, however, were not found to be affected by CO2 concentrations, either CO2 is saturating energetically as mentioned by Lorenzo, or heat is returning to the plate and being emitted at other IR wavelengths.
  39. There is no consensus
    re #171, neil the evidence indicates that there has been substantial acceleration in glacier mass loss since the 1970s. A detailed study of Alpine glaciers was published by the World Glacier Monitoring Service in Zurich a couple of years ago: Haeberli W et al. (2007) Integrated monitoring of mountain glaciers as key indicators of global climate change: the European Alps Annals of Glaciology 46,150-160 Abstract: The internationally recommended multi-level strategy for monitoring mountain glaciers is illustrated using the example of the European Alps, where especially dense information has been available through historical times. This strategy combines in situ measurements (mass balance, length change) with remote sensing (inventories) and numerical modelling. It helps to bridge the gap between detailed local process-oriented studies and global coverage. Since the 1980s, mass balances have become increasingly negative, with values close to -1 m w.e. a(-1) during the first 5 years of the 21 st century. The hot, dry summer of 2003 alone caused a record mean loss of 2.45 m w.e., roughly 50% above the previous record loss in 1998, more than three times the average between 1980 and 2000 and an order of magnitude more than characteristic long-term averages since the end of the Little Ice Age and other extended periods of glacier shrinkage during the past 2000 years. It can be estimated that glaciers in the European Alps lost about half their total volume (roughly 0.5% a(-1)) between 1850 and around 1975, another 25% (or 11% a(-1)) of the remaining amount between 1975 and 2000, and an additional 10-15% (or 2-3% a(-1)) in the first 5 years of this century. And this analysis of glacier mass balance has recently been extended to a worldwide set of glaciers in which mass balance of 228 glaciers with full or partial records back to the 1940’s has been analyzed. This also indicates that after a relative lull in net glacier mass balance in the period around 1960 to 1975 there had been a marked acceleration in glacier mass balance loss. Zemp, M. et al. (2009) Six decades of glacier mass-balance observations: a review of the worldwide monitoring network Annals of Glaciology 50, 101-111 e.g the the authors state that the 30 reference glaciers where there are high quality continuous records show “an accelerated thinning, with mean annual ice loss of 0.14 m w.e. (1976-85), 0.25 m w.e. (1986-95) and 0.58 m w.e. (1996-2005)…. So the loss of glacier mass balance certainly seems to have increased rather markedly since the 1970’s. A brief account of this can be found here: http://www.sciencedaily.com/releases/2009/01/090129090002.htm Likewise, analysis of the Greenland and Antarctic ice sheets indicates a continued acceleration of mass balance loss: e.g. Velicogna, I. (2009), Increasing rates of ice mass loss from the Greenland and Antarctic ice sheets revealed by GRACE Geophys. Res. Lett. in press “We find that during this time period [April 2002 and February 2009] the mass loss of ice sheets is not constant, but accelerating with time, i.e. that the GRACE observations are better represented by a quadratic trend rather than a linear one, implying that the ice sheets contribution to sea level becomes larger with time. In Greenland, the mass loss increased from 137 Gt (gigatonnes)/yr in 2002-2003 to 286 Gt/yr in 2007-2009, i.e. an acceleration of -30 +/- 11 Gt/yr^2 in 2002-2009. In Antarctica the mass loss increased from 104 Gt/yr in 2002-2006 to 246 Gt/yr in 2006-2009, i.e. an acceleration of -26 +/- 14 Gt/yr^2 in 2002-2009. There aren't any press releases for this study yet I think, but related work is decribed here: http://www.sciencedaily.com/releases/2008/11/081129094609.htm http://www.sciencedaily.com/releases/2009/06/090612092741.htm
  40. Philippe Chantreau at 02:35 AM on 11 October 2009
    How do we know CO2 is causing warming?
    Thingadonta, you seem to suggest that the oceans could somehow selectively absorb IR in the same bands as GH gases, so as to mimic the GH effect. How exactly would that be physically accomplished? Furthermore, the Philipona and Evans papers examine downward LW radiation, how would increased ocean absorbtion lead to increased downward radiation?
  41. How do we know CO2 is causing warming?
    #19. LorenzoG said: "O2, N2, H2O all radiate at different wavelengths than CO2, and your chart above doesn't even cover two of the H2O bands. Unless you analyze the total energy exchange by the Earth on all wavelengths you can't begin to come to any conclusions." If there is a measured difference in CO2 bands (such as the one measured by Harries et al. in their few studies), possible differences in H2O bands don't change that, the CO2 difference remains the same. "The three primary IR absorption peaks of CO2 only cover about 8% of the infrared band, so CO2 is transparent to 92% of infrared energy." Which also doesn't take away anything from CO2 absorption. Nobody is claiming that CO2 absorbs whole of infrared band. "The Philipona paper mentioned above indicates a 1.8W/m2 increase in energy being radiated towards the ground. The sun sends ~1,000W/m2 at the equator. The increase described by Philipona is 0.18% of the sun's output. Can you prove that there has not been 1/5 of 1% variance in the sun's output over the last 34 years?" The 1.8 W/(m^2) number in Philipona et al. is for downward longwave radiation, but the number you give for the sun is for total sunlight, not only for longwave band. Try again.
  42. Scientists can't even predict weather
    An analogy that I like to make is to the seasonal cycle. For example, if I told you that I could predict with confidence the weather here in Rochester for a day three weeks hence, you would correctly laugh at me. However, if I told you that I could predict with confidence that the average temperature for next January will be roughly 40 F colder than it was in July, I don't think you would give me much of an argument. It is also worth noting that the chaotic behavior of the weather can be tested with the numerical weather prediction and climate models. For example, a numerical weather prediction model will give a specific weather prediction for a day 3 weeks hence, but if you run it again with just small perturbations to the initial conditions, the prediction will be very different. (Actually, such running of ensembles with perturbed initial conditions now plays an important role in weather forecasting, at least for the period out beyond a few days.) On the other hand, I assume that such a model will give a reasonable prediction for the climate in January relative to July and the basic features will not be sensitive to the initial conditions. Likewise, with a particular climate model, perturbed initial conditions result in differences in the "jiggles" of the global temperature but when run out for 100 years, the different realizations all predict roughly the same overall amount of warming. This is true because the warming that occurs is governed by the fundamental issue of radiative balance between the earth, sun, and space. (Admittedly, because of feedback effects, determining how that radiative balance plays out is not easy...but it does not seem to be sensitive to small perturbations in initial conditions.)
  43. Philippe Chantreau at 18:36 PM on 10 October 2009
    How do we know CO2 is causing warming?
    Lorenzo, the Max Planck Institute TSI reconstruction shows a variance of about 0.8 w/m2 since 1885 (0.2 w/m2 on Earth surface), no net increase over the past 35 years. That reconstruction uses an 11 year average that removes the variations from the solar cycle. Both PMOD and ACRIM show cyclic variations no greater than roughly 2w/m2 (no trend over the observation period), which translate into a surface forcing +/- 0.5 w/m2. We're talking total irradiance here, not the IR part. Considering how small TSI changes are and considering how much of TSI is in the IR spectrum and at which wave lengths, I'm wondering how your question #4 can make sense.
  44. Philippe Chantreau at 16:17 PM on 10 October 2009
    Are humans too insignificant to affect global climate?
    Increased CO2 is such a minor factor compared to water availability and nutrients, it's not even worth considering from a practical point of view. Water vapor itself is also very minor. Changes in rain patterns associated to the climate changes brought by increased CO2 are much more likely to affect plants than the level of CO2 itself. We're not talking about a greenhouse or lab where every single parameter can be finely controlled here. Availability of liquid water and nutrients are the real important things. Ther rest is nit picking. I'd like to see the reference on that increase in plant life study, especially to see if there is any attribution to possible causes in the increase. I'm also wondering what exactly is meant by "increase." I believe that land use changes are more likely than any other factor to yield that kind result. I seriously doubt that "CO2 fertilization" (an abuse of language really) can be that effective.
  45. How do we know CO2 is causing warming?
    LorenzoG wrote in #19: "2.) Doubling the CO2 level in the atmosphere will not result in any more energy being trapped in the atmosphere because ALL OF IT IS ALREADY ABSORBED." That myth is ancient--as in the turn of the 19th century to the 20th century. See A Saturated Gassy Argument.
  46. How we know global warming is still happening
    shawnhet, "Cloud formation depends on RH, but also on the specific humidity. The more water in air, the thicker and deeper will be the clouds that form *once that air cools sufficiently*. There will be more water condensed out of air cooling from 16C to 15C (when everything else is equal) than air cooling from 15C to 14C. If everything else were really equal, then this should lead to correspondingly higher amount of clouds." Why is that? At a given specific humidity the relative humidity will depend upon the saturation vapor pressure and that in turn is dependent on temperature. The higher the temperature the greater the saturation vapor pressure and lower the RH at a given specific humidity. The GCM's indicate that as global average temperature rises so does specific humidity in such a way that RH remains nearly constant (Clausius-Clapeyron relation) or maybe a bit lower. The tendency to form clouds begins at around 70% RH no matter the temperature or specific humidity. You are correct that more water can potentially be condensed out at higher specific humidities where clouds do form, but this relates to precipitable water within the column of atmosphere (because the water load is greater), not necessarily to the tendency for cloud formation.
  47. Philippe Chantreau at 12:05 PM on 10 October 2009
    Are humans too insignificant to affect global climate?
    Increased CO2 is such a minor factor compared to water availability and nutrients, it's not even worth considering from a practical point of view. Water vapor itself is also very minor. Changes in rain patterns associated to the climate changes brought by increased CO2 are much more likely to affect plants than the level of CO2 itself. We're not talking about a greenhouse or lab where every single parameter can be finely controlled here. Availability of liquid water and nutrients are the real important things. Ther rest is nit picking. I'd like to see the reference on that increase in plant life study, especially to see if there is any attribution to possible causes in the increase. I'm also wondering what exactly is meant by "increase." I believe that land use changes are more likely than any other factor to yield that kind result. I seriously doubt that "CO2 fertilization" (an abuse of language really) can be that effective.
  48. How do we know CO2 is causing warming?
    This article ignores basic science. 1.) OK, so a CO2 absorbs a photon of infrared. The only ways that molecule can de-energize to be ready for the next photon is to conduct heat away through impact with another molecule, or to re-radiate it out at the same frequency. Either it does one of these or all CO2 molecules will soon reach saturation and be unable to absorb more infrared. If it conducts it to another molecule then that molecule will either conduct it away again or re-radiate the photon, BUT AT THAT MOLECULE'S WAVELENGTHS, not CO2's. O2, N2, H2O all radiate at different wavelengths than CO2, and your chart above doesn't even cover two of the H2O bands. Unless you analyze the total energy exchange by the Earth on all wavelengths you can't begin to come to any conclusions. 2.) Dr. Heinz Hug's work suggests that CO2 is such a good absorber of infrared energy that it absorbs 100% of IR radiated from the ground at your 650/cm region within 10 meters of the ground. Doubling the CO2 level in the atmosphere will not result in any more energy being trapped in the atmosphere because ALL OF IT IS ALREADY ABSORBED. You won't get twice the heating from doubling the CO2 concentration because there is none left to absorb at that wavelength. 3.) The three primary IR absorption peaks of CO2 only cover about 8% of the infrared band, so CO2 is transparent to 92% of infrared energy. 4.) The Philipona paper mentioned above indicates a 1.8W/m2 increase in energy being radiated towards the ground. The sun sends ~1,000W/m2 at the equator. The increase described by Philipona is 0.18% of the sun's output. Can you prove that there has not been 1/5 of 1% variance in the sun's output over the last 34 years?
    Response: If the CO2 effect was saturated, then increasing CO2 would lead to no change in the greenhouse effect. As satellite measurements (Harries 2001, Griggs 2004, Chen 2007) and surface measurements (Philipona 2004, Evans 2006) all find an enhanced greenhouse effect at the CO2 and CH4 bands, this is empirical confirmation that the CO2 effect is not saturated.

    Note that hotter objects emit radiation at shorter wavelengths. Hence the sun emits shortwave radiation while the earth emits longwave radiation. This is the basis of the greenhouse effect - shortwave radiation from the sun passes through the atmosphere, warms the earth which then emits longwave radiation back out to space. This longwave radiation is absorbed by greenhouse gases. The enhanced greenhouse effect observed by the papers listed above are at longwave wavelengths, not shortwave. It's basic science.
  49. Are humans too insignificant to affect global climate?
    The fact is, that plant growth has a number of constraints on it and if you relax a constraint then growth will increase, unless there is another constraint that is blocking it. If the plant is primarily constrained by the amount of liquid water it is exposed to(or the nature of the soil it is sitting in), then adding more CO2 will not help it grow. However, for the plants that are(currently) constrained by the speed/efficiency they can remove carbon from the air, then increasing CO2 will help them grow. This is why commercial greenhouses routinely pump massive levels of CO2 into their structures(they are designed to relax as many constraints on plant growth as possible). Clearly, some plants, in their current environments would grow faster(and, hence bigger) if they had access to more CO2. Further, this is compounded by the fact that warming temps will also yield more WV which also makes it easier from plants to grow, on average. IIRC, this effect has been measured from space, and there has been something approximating 6% increase in plant life on Earth over the last 20+ years. Cheers, :)
  50. How we know global warming is still happening
    WeatherRusty:"It is not a given that there are more clouds in a generally warmer environment. Cloud formation depends very much on relative humidity and also the availability of lift within the atmosphere, warm moist air must rise and cool to near it's dew point. A product of all climate simulations is a near constant relative humidity as the climate warms. Look at the tropics and near tropics today. Most cloud formation is convective in nature and where this is the result of daytime heating the clouds dissipate at night. The tropics receive the vast majority of solar radiation but cloudiness does not prevent that region from being the warmest on Earth. If the climate zones and jet streams are shifted poleward in a warming world why would the dynamics be any different in their displaced positions?" Cloud formation depends on RH, but also on the specific humidity. The more water in air, the thicker and deeper will be the clouds that form *once that air cools sufficiently*. There will be more water condensed out of air cooling from 16C to 15C (when everything else is equal) than air cooling from 15C to 14C. If everything else were really equal, then this should lead to correspondingly higher amount of clouds. The fact that clouds form quickly and easily in the tropics doesn't prevent them form being the hottest place on Earth(on average), but it does help prevent them from getting as hot as land at the same latitude (during the day). Further, it is not a given that RH is, in fact, a constant either. Cheers, :)

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