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The human fingerprint in global warming

What the science says...

Select a level... Basic Intermediate Advanced

Multiple sets of independent observations find a human fingerprint on climate change.

Climate Myth...

It's not us

'What do the skeptics believe? First, they concur with the believers that the Earth has been warming since the end of a Little Ice Age around 1850. The cause of this warming is the question. Believers think the warming is man-made, while the skeptics believe the warming is natural and contributions from man are minimal and certainly not potentially catastrophic à la Al Gore.' (Neil Frank)

When presented with the overwhelming evidence that the planet is warming, many people react by asking "but how can we be sure that we’re causing the warming?" It turns out that the observed global warming has a distinct human fingerprint on it.

In climatology, as in any other science, establishing causation is more complicated than merely establishing an effect. However, there are a number of lines of evidence that have helped to convince climate scientists that the current global warming can be attributed to human greenhouse gas emissions (in particular CO2). Here are just some of them:

10 Indicators of a Human Fingerprint on Climate Change

The first four pieces of evidence show that humans are raising CO2 levels:

  1. Humans are currently emitting around 30 billion tonnes of CO2 into the atmosphere.
  2. Oxygen levels are falling as if carbon is being burned to create carbon dioxide.
  3. Fossil carbon is building up in the atmosphere. (We know this because the two types of carbon have different chemical properties.)
  4. Corals show that fossil carbon has recently risen sharply.

Another two observations show that CO2 is trapping more heat:

  1. Satellites measure less heat escaping to space at the precise wavelengths which CO2 absorbs.
  2. Surface measurements find this heat is returning to Earth to warm the surface.

The last four indicators show that the observed pattern of warming is consistent with what is predicted to occur during greenhouse warming:

  1. An increased greenhouse effect would make nights warm faster than days, and this is what has been observed.
  2. If the warming is due to solar activity, then the upper atmosphere (the stratosphere) should warm along with the rest of the atmosphere. But if the warming is due to the greenhouse effect, the stratosphere should cool because of the heat being trapped in the lower atmosphere (the troposphere). Satellite measurements show that the stratosphere is cooling.
  3. This combination of a warming troposphere and cooling stratosphere should cause the tropopause, which separates them, to rise. This has also been observed.
  4. It was predicted that the ionosphere would shrink, and it is indeed shrinking.

(References for all of these findings can be found here.)

Often one hears claims that the attribution of climate change is based on modeling, and that nobody can really know its causes. But here we have a series of empirical observations, all of which point to the conclusion that humans are causing the planet to warm.

Basic rebuttal written by James Wight

Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial


Last updated on 8 July 2015 by MichaelK. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

Argument Feedback

Please use this form to let us know about suggested updates to this rebuttal.

Further reading

Professor Scott Mandia has a detailed explanation of why more CO2 causes stratospheric cooling that is well worth a read.


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Comments 51 to 78 out of 78:

  1. As well as nights warming faster than days, I would add winter warming faster than summer (if it was the sun, it would be the other way around), mentioned in the Scientific Guide to Global Warming Skepticism.
  2. In the advanced version of The human fingerprint in global warming dana1981 writes: "Trenberth et al. (2009) used satellite data to measure the Earth's energy balance at the top of the atmosphere (TOA) and found that the net imbalance was 0.9 Watts per square meter". This proposition is false. What Trenberth has actually found in said paper is this: "There is a TOA imbalance of 6.4 W m−2 from CERES data and this is outside of the realm of estimates of global imbalances that are expected from observed increases in carbon dioxide and other greenhouse gases in the atmosphere" That is, Trenberth says satellite data are useless for measuring Earth's energy balance. Then he continues: "The TOA energy imbalance can probably be most accurately determined from climate models and is estimated to be 0.85 ± 0.15 W m−2". So. The energy imbalance is not measured, it is determined using computational climate models. Then, what he actually did to satellite data is described like this: "An upper error bound on the longwave adjustment is 1.5 W m−2, and OLR was therefore increased uniformly by this amount in constructing a best estimate. We also apply a uniform scaling to albedo such that the global mean increase from 0.286 to 0.298 rather than scaling ASR directly, as per Trenberth (1997), to address the remaining error. Thus, the net TOA imbalance is reduced to an acceptable but imposed 0.9 W m−2 (about 0.5 PW)". That is, he increased both OLR and albedo relative to actual data by amounts he considered acceptable in order to arrive at an imposed value of TOA imbalance. Therefore it's not true he has "found that the net imbalance was 0.9 Watts per square meter", but took a value based on model calculations and imposed it on satellite measurements. What Trenberth did is questionable, but defensible in a sense. Whenever you have next to useless data with unknown but large error margins, you either throw it away or do odd things to it in the hope at least something can be saved. If the data are as expensive to collect as CERES data are, NASA scientists have no choice but follow the latter path. On the other hand grave misrepresentation of Trenberth's pain as it is put by dana1981 above, is indefensible. Calculations can be verified against measurements, but they can never be verified against (the same!) calculations. That is, Trenberth's figure of 0.9 W/m2 net imbalance at TOA is still an unverified claim. There is an important difference in science between true and false statements. The latter kind implies anything along with its own negation, therefore it's a bit ill suited for deriving meaningful results.
  3. Dikran, KR + Julian. I have no background in climate, I'm a computer scientists; loving your debate. KR is correct in saying that since we did add 'xyz' amount of CO2, then it is humans who can be attributed to that amount - but KR/Dikram - Julian is correct to point out that it could be entirely meaningless. KR you are throwing straws on the camel's back, maybe you broke the camels back, Julian is pointing out that your straws - though technically 'added' are irrelevant given that others were adding and removing straws from the camels back by an unknown amount. KR - Julian is not proposing a 'Green Little Man' argument - he's indicating that the other sources/sinks for CO2 could indeed be quite vast. If they are - and they are highly variable - then his assertions are not only correct, but meaningful. You are sharing a bank account with a 'black box'. You know the black box withdraws and adds X amount every month. You know that you add $16 every month. The bank account seems to be rising by ~$16 every month. You know for sure that the 'black box' NET contributions monthly are 0 - but you have no idea why, or what the net attributions are. To KR's point, it is reasonable to conclude that since you are adding $16 every month - well - you are adding $16 every month - no doubt about it. KR is technically correct - but his point may be mute. Julian's point is that the black-box may be inserting/removing 1000's every month - you don't know. If this is the case - then KR your point is mute - it doesn't matter if we are adding $16 a month. Dikram, your analysis would be off. The Dikram/KR/Julian debate boils down to this: If the plus/minus CO2 contributions via sinks/sources from 'non man made sources' (I'n not going to use the proper scientific term since I'm not sure of it's meaning) is rather large, and it varies quite a lot over time - then Julian's position is not only technically correct, but it is very valid. If those net contributions can be definitely characterized as stable and small, then we can safely follow Dirkam's points on the matter and KR's point that 'we are adding X amount every year' matters - because our contributions are meaningful. I'm guessing however, that we don't really understand the size and magnitude of these other heat-sinks, and that they may be highly variable. If this is the case then Julian's point should be considered. KR is technically correct but his point is mute - and Dikram's analysis must be flawed.
  4. jomamax - I would have to forcefully disagree. If we know: * We are contributing X to the bank balance * We know the total balance to be increasing at X/2 Then: * Other contributions and deductions from that balance are such that other contributions are X/2 less than deductions; that the other influences on the balance are a net sink. It doesn't matter how much those other contributions/deductions vary in toto - the difference between them is established to be negative X/2 by observing our contributions and the total balance. By knowing how much CO2 we put out and how much the atmospheric levels increase - we know two of the four values, and hence we really do know the difference between the other two. Stable, varying, whatever; it just doesn't matter. We know what the difference is between the natural sinks and sources, and it adds up to about half of our emissions - nature is a net sink. There's just no other way possible to work the math, barring Little Green Men (LGM's) adding or subtracting carbon from the biosphere. And if you make that kind of causal assertion, well, I'm going to feel completely justified at laughing...
  5. This debate is also going on in the Murray Salby thread. jomamax: you have several "ifs" that are "aren'ts". 1) "black-box may be inserting/removing 1000's every month - you don't know.". Yes, we do know, with a fair degree of accuracy (but not perfectly). The known fluxes in the carbon cycle don't have error bars that large. 2) "If the plus/minus CO2 contributions via sinks/sources from 'non man made sources' (I'n not going to use the proper scientific term since I'm not sure of it's meaning) is rather large, and it varies quite a lot over time". It is large, but it's not varying that much over time - at least, not in amounts that we don't know about (point 1). CO2 was fairly steady (with a seasonal cycle) for a long time before people started burning fossil fuels, and we know a lot about the cycles. 3) "If those net contributions can be definitely characterized as stable and small,". They don't need to be small, and they don't need to be stable for us to have reasonable estimates of them. You'd need to have large, variable errors in the measurements of those fluxes, and that's not the case (point 1). 4) "I'm guessing however, that we don't really understand the size and magnitude of these other heat-sinks". You'd be guessing wrong. (I presume you meant CO2 sinks.) In addition, you have to remember that in the bank balance scenario, you are also using marked bills. Unless the other sources/sinks are marking the bills exactly the same way, the source is obvious. CO2 from fossil fuels is depleted in C14, and has a C12/C13 mix that does not match other sources of CO2 that are depleted in C14.
  6. jomamax The mass balance argument is correct regardless of how large natural emissions are. It is easy to show why this is true using the savings analogy. Say I share a savings jar with my wife (who represent the natural environment), that is guarded by loyal ninja to make sure only she and I can make deposits and withdrawals. If I put in $16 a month and notice that our savings rise by only $8 a month, then I know that my wife is spending $8 more a month than she is saving. This is true whether she saves $1 a month and spends $9, or if she saves $10 a month and spends $18, or if she saves $100 a month and spends $108, ..., or if she save $1,000,000,000 and spends $1,000,000,008. As it happens, we do know that natural emissions are much larger than anthropogenic emissions. We know this because the residence time of CO2 in the atmosphere is only 4-5 years, which means there must be a very large exchange flux that swaps about 20% of atmospheric CO2 each year with CO2 from the oceans and terrestrial biota. However this exhange is just that, a straight swap of CO2 between reservoirs, and has no effect whatsoever on atmospheric CO2 concentrations. As Murray Salby says, it is only the difference between total emissions and total uptake that matters, and the mass balance equation shows that even if natural emissions are much bigger than anthropogenic emissions, natural uptake is bigger still. This means the natural environment is actively opposing the rise. If you think Julian is right and the absolute magnitude of natural emissions matters (rather than the difference between natural emissions and natural uptake), then it should be possible for you or Julian to come up with a counter example, in the form of values for natural emissions, natural uptake, anthropogenic emissions and the annual rise in CO2, where the natural environment is a net carbon source and the observed rise is less than anthropogenic emissions, and doesn't violate conservation of mass. You will find that you can't. Note I challenged Julian to do so, and he ducked the challenge, and did not reply to my post pointing out that he had ducked the challenge.
  7. Hi and thank you all for this very interesting and enlightening discussion. Great website here! If I understand correctly, the LGM ("little green men") point is the key point here. The mass balance is right by logic, but I think Julian points out that the mass balance may not be all about it (might be "the wrong level of abstraction") because nature sources/sinks might not be as constant as we assume. Let me try the challenge issued by Dikran: year 1: +70.000 natural +200 humans -70.100 natural -> +100 year 2: +70.000 natural +0 humans -70.100 natural -> -100 so far the mass balance argument, as I understand it. Now suppose the "little green men" like this: year 3: +70.000 natural +0 humans -69.900 natural -> +100 or, with human contribution still in the picture, like this: year 2bis: +70.000 natural +200 humans -70.050 natural -> +150 What has happened here? Little green men? Yes, but natural little green men, if you will. In year 3, human is still +0, but a natural sink suddenly decreased, by a small amount. Or, alternatively, in year 2bis, human is still contributing, but natural sinks have suddenly decreased. This is outside the mass balance argument, but this seems to be Julian's point: Nature's part is so huge in comparison, that even small fluctuations may happen arbitrarily, which completely make human's part arbitrary in the long term picture. Julian, does this capture your point? Of course, this is just about that the mass balance argument alone is not enough. If we add indications, theories and evidence, we should be back to the result that human contribution is decisive, because any such thinkable natural fluctuations have not been evidenced so far. And I think that is the core of Julian's criticism. Is that conclusion from evidence valid? Basically, you all here point out, yes. But why? But this refers to a point made from outside the mass balance logic, so maybe we should admit to that the mass balance argument alone is not proof, but rather strengthens existing evidence? If we came so far, how exactly is existing evidence strengthened by the mass balance? Because the past shows us clearly a constant natural net (200ppm), until human contribution kicks in (to 395ppm)? How do we know human contribution is +195ppm? If I understand correctly, fossil isotopes in the atmosphere are only about 5%, which would be roughly 20ppm. So, there is even more evidence to be linked. Which?
  8. Falkenherz, I believe Tom Curtis has addressed some of this recently here. It should probably be incorporated into this article.
  9. DSL, I read it, and it provides for several indicators of evidence. But I meant specifically the mass balance argument, and the comments here provide for much more detail already than in that article. I, as Julian, might just have a gap of logic here, and I hope that listing these very simplified figures will make it clear for me, if someone can point it out where they goe offroad.
    Response: [DB] A deeper-level analysis of the mass-balance problem for "skeptics" is found here.
  10. Thanks, I will be commenting over there.
  11. Falkenherz, the problem is that your example assumes we only know one variable... the total atmospheric accumulations (the end result of each of your calcualtions). That is incorrect. We know accumulations and human emissions. The mass balance argument only works when using both of those values. Thus, your counter argument is 'correct' only if we ignore some of the data we have.
  12. I wrote to Prof Essenhigh a couple of years back when his paper came out. Not having received a response since, I thought I'd write an open letter to him: Open letter to Prof Essenhigh Brilliant that there's a peer review response now (Skeptical Science's Dikran Marsupial's response)
  13. Response to Sphaerica from 'Inuit Perspectives on Recent Climate Change' - transferred to this thread at moderator's request. Sphaerica: Just to reinforce my point – more observations from the real world. Ice conditions in the Baltic Sea vary a lot from one year to another. The maximum ice covered area varies between 52,000 and 422,000 square kilometres(12-100 per cent of the total Baltic Sea area) Baltic Sea Portal: Clearly the Baltic Sea has remained free of the malign influence of CO2. Here’s more: JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 106, NO. C3, P. 4493, 2001 doi:10.1029/1999JC000173 'Influence of atmospheric circulation on the maximum ice extent in the Baltic Sea' Anders Omstedt Swedish Meteorological and Hydrological Institute, Norrköping, Sweden Deliang Chen Department of Earth Sciences, University of Göteborg, Göteborg, Sweden This work analyzes long-term changes in the annual maximum ice extent in the Baltic Sea and Skagerrak between 1720 and 1997. It focuses on the sensitivity of the ice extent to changes in air temperature and on the relationships between the ice extent and large-scale atmospheric circulation. A significant regime shift in 1877 explains the decreasing trend in the ice extent. The regime shift indicates a change from a relatively cold climate regime to a relatively warm one, which is likely a result of changed atmospheric circulation. In addition, the analysis shows that a colder climate is associated with higher variability in the ice extent and with higher sensitivity of the ice extent to changes in winter air temperature. Moreover, the ice extent is fairly well correlated with the North Atlantic Oscillation (NAO) index during winter, which supports the results of earlier studies. However, the moving correlation analysis shows that the relationship between the NAO index and the ice extent is not stationary over time. A statistical model was established that links the ice extent and a set of circulation indices. It not only confirms the importance of the zonal flow but also implies the impact of meridional wind and vorticity. The usefulness of the statistical model is demonstrated by comparing its performance with that of a numerical model and with independent observations. The statistical model achieves a skill close to that of the numerical model. We conclude that this model can be a useful tool in estimating the mean conditions of the ice extent from monthly pressures, allowing for the use of the general circulation model output for predictions of mean ice extent. Finally, the globe is warming? Is it?
  14. Carbon500 - With regards to your extended reference, yes, ice extent certainly does vary based on a number of influences. Relevance? In regards to the graph you refer to, containing temperature data only from 1996, I would refer you to the Did global warming stop in 1998, 1995, 2002, 2007, 2010 thread. Cherry-picking short intervals proves nothing about long term trends - that's weather. If you look at those long term trends, however, at climate, you see something quite different (GISTEMP and 10 year averages).
  15. Carbon500, Sorry, but your gish-gallop is 100% silliness. My original point was: "And what evidence do you have that your anecdotal evidence is equivalent to what we are seeing today?" And you respond with yet more anecdotal evidence, in this case, a narrowly focused view of ice in one part of the world, as if that is then evidence that the entire globe is not warming. I'm sorry, Carbon500, this is a 100% fail. You're going to have to try a lot harder than just listing whatever papers you can find with google-search.
  16. Carbon500, from your post here: I've seen a reproduction of this quote in quite a number of places - it seems to be a bit of a darling quote of the so-called 'skeptics' - a report from the early 20th Century indicating that conditions in the Arctic are notably warmer than in the late 19th Century. You quoted this as though it's somehow surprising or that it refutes anthropogenic causes for global warming. A 1920s observer in the Arctic might notice that, compared to the late 19th Century, glaciers had retreated somewhat and that sea ice was reduced in extent. An observer in the early 21st Centuey can observe that the same glaciers are considerably further back and continuing to retreat at a rapid rate [Some slightly readvanced in the 1960s-1980s in response to favourable conditions in the 1960s and 1970s]. A 21st Century glacial geomorphologist can observe that glaciers in Iceland, Norway, the Alps and elsewhere reached their greatest "Little Ice Age" extent in the late 19th Century (historical records, lichenometry etc) leaving large moraines behind. This is no surprise! We know there has been warming sice at least the late 19th Century. We have a pretty good idea of the causes of the warming through the 20th century: early warming had a large component of solar activity and a reduction in volcanic activity in addition to the initial component of post-Industrial Revolution greenhouse gas emissions. As we moved through the 20th Century, the GHG forcing increased to be the strongest of all the forcings, such that we cannot explain our current trajectory of warming if we ignore GHG physics (unless you believe in climate fairies, which I don't). The Arctic is continuing to respond to those forcings. The skeptics' claims that early 20th Century observations of the beginning of the thaw of the high Arctic, which is contiuing through the present day somehow contradicts our understanding of GHGs and climate, is frankly absurd. It's a transparent attempt to mislead the unwary reader by drawing a false parallel between the 1920s and today. We see that the Arctic is a much less ice-covered place than it was 40 (or 80, or 120 years ago), an observer in the 1920s saw that the Arctic was less ice-covered than in the 1880s. That 1920s observer would be astonished to see how little ice is in the Arctic now compared to the 1920.
  17. KR: The point I made is that ice melting depends on many influences, and I think that caution is needed when attributing ice melt extent to CO2. That’s why I gave the Omstedt and Chen reference as an example. Regarding global temperatures, I am of course aware of the other graphs you mention, and the argument that the current stalling of warming is too short a period from which to draw firm conclusions – and yes, I am aware of the difference between weather and climate. (-snip-)? Sphaerica: (-snip-). Skywatcher: We agree that warming has in essence been in progress since the 19th century, but I’m more cautious than you about the 20th century. (-snip-). Another reason for my caution goes further back in the climatic record. (-snip-) Clearly Nature can surprise us. (-snip-) (-snip-). (-snip-)?
    Response: [DB] Multiple off-topic and inflammatory snipped. As constructed, this comment comprises a Gish Gallop. Future such comments will be deleted in their entirety.
  18. Carbon500 - In some respects the graph you posted earlier is very interesting. Go to the Temperature Trends tool here, and look at GISTEMP (I will note in passing that you did not identify the source of your graph, or the selections from which it was generated - very bad form). Set a starting point of 1996 and smoothing of 1 month, as per that graph (source identified only from the URL), and look at the trend. 2σ uncertainties are calculated with added uncertainty due to autocorrelation, so this is a reasonably conservative estimate. Trend: 0.123 ±0.130 °C/decade (2σ) What does this set of data mean? There is a temperature trend of 0.123°C/decade, but it is is not quite statistically significant over that period. More data, more time is needed to truly distinguish that trend from the null hypothesis of no warming. But even your "no warming" example actually shows warming consistent with 30 and 40 year trends. Your claim that "this sixteen year old record cannot be ignored" is a strawman argument (it's not ignored, but it's not statistically significant - it's part of the data that is statistically significant), and indicates that you are lacking in statistical insight - as your presented evidence contradicts your claims (since it indeed shows warming). In other words, your use of that graph in an attempt to claim no warming is (IMO) quite demonstrative of denial myths - myths that sources like SkS are (I am happy to see) working to dismiss as the silliness they are. Finally, regarding experimental evidence of CO2 trapping heat - take a look at Harries 2001 directly showing energy entrapment at CO2 frequencies, which is discussed here regarding incremental effects as well as here regarding empirical evidence. If you disagree with the evidence, present your evidence on the appropriate threads. WRT water vapor, search using the SkS "Search" box for water vapor, or look at Google Scholar. Your claim that the role of CO2 as a greenhouse gas hasn't been experimentally proven is, to be blunt, complete and unsupported nonsense.
  19. KR: Sometimes it's useful to stand back and just look at the contours of a graph rather than playing games with trend lines and placing all your faith in statistical results. I have a good reason for saying this. In an industrial research project on which I was engaged many years ago the statistics of a crucial experiment showed significance (and yes the correct test was used, in case you're wondering), but because I was suspicious further experiments ensued and a great deal of time and money was subsequently saved on the project on which I was engaged. The section of graph I'm talking about is quite different in character from what precedes it. Never mind, you look at it your way, I'll look at it mine. Where have I made the claim that the role of CO2 as a greenhouse gas hasn't been experimentally proven? Have I even suggested that I have issues with satellite data? Had you read what I said properly, you would have noted that I was enquiring as to whether a laboratory experiment using an artificial atmosphere had ever been carried out to assess the effects of CO2.
  20. Carbon500 wrote: "Sometimes it's useful to stand back and just look at the contours of a graph rather than playing games with trend lines and placing all your faith in statistical results." So... avoid any hint of actual math and just let your preconceived notions guide your 'understanding' of the data? "The section of graph I'm talking about is quite different in character from what precedes it." True, in that it does not show as rapid an increase in atmospheric temperatures... but you implied ("Finally, the globe is warming? Is it?") that it doesn't show an increase at all, which is simply false. Even if it weren't false it would be the wrong graph for what you purport to be disputing. That's a graph of lower atmospheric temperatures, not "the globe". The oceans of the world are a vastly greater reservoir of energy than the lower atmosphere... and measurements of ocean water continue to show a high rate of warming. Finally, even if we could use just the lower atmosphere to determine whether the globe was warming, while ignoring the vastly more significant oceans, and we pretended that the lower atmospheric graph you posted did not show the warming trend it actually does... your 'conclusions' would still be wrong because there has been extensive research on the various factors at play in atmospheric temperatures over the past hundred years and the 'difference in character' you note has been explained by measured changes in factors other than the greenhouse gas forcing. Basically, greenhouse gas warming continues to increase and is the primary driver of the continuing warming trend. The short term variability you cling to is the result of other smaller factors (e.g. solar radiation, volcanic eruptions, soot, et cetera) varying up and down enough to change the slope of the trend over short time frames... but not enough to stop the inexorable upwards march.
  21. Carbon500 - "Where have I made the claim that the role of CO2 as a greenhouse gas hasn't been experimentally proven?" Let me refresh your memory. In your last post, which I replied to before it was snipped for being a Gish Gallop, you said:
    Does this really mean that the foundation stone of the CO2 story hasn’t been verified experimentally, and that calculated forcings are all the evidence there is?
    You did indeed make that claim - and it is indeed completely unsupportable given direct evidence such as Harries 2001.
  22. KR: It depends on what you mean by an experiment. To me an experiment is something which has been set up so that variables can be controlled by the experimenter, hence my comments regarding an artificial atmosphere. CBDunkerson: the graph I'm talking about is entitled 'Monthly Mean Global Surface Temperature'- you don't agree with the way I see it; so be it. (-snip-)
    Response: [DB] Off-topic snipped. Please follow the link that Adelady was kind enough to provide for a discussion of that newspaper article.
  23. carbon500, You need to check out the latest SkS post.
  24. Carbon500, if you make reality a matter of perception then we have no common basis for discussion. Either the globe consists of more than the surface atmosphere (e.g. oceans, higher layers of the atmosphere, et cetera) or it does not. Either the graph you posted showed a warming trend or it did not. If you truly believe the 'not' position on either of these issues then 'the way you see it' is at odds with perceived reality 'the way I see it'.
  25. adelady: thank you for your comment. CBDunkerson: I agree - clearly we have no common basis for discussion. Ditto KR.
  26. " clearly we have no common basis for discussion" Sorry, you saying that your graph does not show a warming trend despite it being demonstrated that it does and that you believe the globe only consists of surface atmosphere? You are admitting that you prefer your preconceptions to reality? Not many people have been prepared come right out and say that.
  27. @Julian Flood

    Suppose we have a sink into which the faucet is pouring water.We have control of the faucet and can increase or decrease its rate of flow. We may not have the political will to do that, but that's a side issue. The point here is that we can. Now let's say that some natural forces are pouring vinegar, pee, alcohol, orange juice, and milk into the sink at the same time our water is pouring in from the faucet. 

    If the water level in the sink is rising at only 45% percent of the rate we would expect from the rate of our input from the faucet, why do you think our lack of knowledge of exactly how much of each of the other inputs and our resulting inability to calculate the sum of their effects is important for understanding whether our faucet is causing the water level to rise?

    If the rate of increase in the level of water is 45% of the rate we would expect from our input from the faucet, we know with absolute certainty that that 55% of our water is going down the drain and all the other inputs with it as well. I don't understand what is so hard to understand about that? Why do you think there is any need for detailed knowledge about the rest of what's going down the drain?

    Now, there is a very significant implication in this. If we know how much CO(2) we're putting out and how much is showing up in the atmosphere (~45% of our input), where is the rest of that CO(2) going? The only reasonable explanation is that the ocean is sequestering the vast majority of it. We do know that the CO(2) level in solution in the ocean has been increasing and ocean water is becoming more acidic. We are also seeing the effects of this on coral reefs and other marine life. As the globe becomes warmer, CO(2) becomes less solube in water, so the 45% figure is bound to go up and accelerate an already undesirabe situation.

    So I don't see where your doubts are coming from unless you just don't want to see and are willing to pick at any single little corner you can find, one at a time and out of context with the bigger picture, simply to avoid seeing.

  28. acjames76 - Moore has quite a list of denial myths, errors, and cherry-picks in that document. 

    First and foremost, he insists on using regional records (Greenland and Vostok) and treating them as global. This includes the rather silly statement "...that global averages are a very poor indicator of actual conditions in either hemisphere." Which is just silly. Regional data will always have higher variations and noise than hemispheric or global signals - any time you see someone preferring a small regional signal to one for a larger area and arguing about global trends, you are seeing cherry-picking fallacies in action. 

    He also compares against lower tropospheric satellite temperatures shown over a period of less than five years - when about 23-24 years are required to identify statistical trends. 

    Cycles, cycles, cycles - all ignoring the (measured) forcing contributions from anthropogenic greenhouse gases, with armwaving such as "Perhaps the forces have to do with cycles in solar radiation and solar magnetism, or cosmic radiation, or something we haven’t yet identified"

    He also throws in the "CO2 is a trace gas", the "clouds", and "CO2 is plant food" myths - all contradicted by the evidence. 

    There's plenty more, but in short he's presented a Gish Gallop of nonsense. Not worth the electrons used reading it...

  29. Also responding to acjames @76, expanding on KR's point, arctic and antarctic regions are known to be more sensitive to changes in temperature than tropical regions due to ice and snow albedo feedbacks.  Dr Hansen estimates that the Vostock (and Dome C) ice cores in Antarctica show local temperature changes twice that of the global mean, and Greenland icecores are even more sensitive.  Nevertheless, taking an average the Greenland and Antarctic icecores is not a bad way to determine the general pattern of global temperature changes, if not the magnitude.  It should be noted in doing so that the fact that you are using only two records and both from polar regions (which have greater temperature variability than tropical regions) will mean that you radically over estimate decadal variability in such an average.  A one hundred year smooth of the data would give a better idea.

    If ignoring the impact of the limited number of sites is bad, when using the data to estimate variability, ignoring polar amplification when comparing with the modern temperature record is absurd.  That, however, is exactly what Richard Moore does.  Here is the chart he produces by appending the global mean twentieth century temperatures to the polar means as determined from icecores:

    The key point here is that to account for polar amplification, we would need to divide the icecore data by two, or equivalently multiply the global data by two for a plausible comparison.  Even that would probably underestimate the ratio of polar to global temperature changes.  Doing so, however, wold increase twentieth century global temperature equivalence to 1.4 C, well above the highest values from the average ice core data.  Further, the highest points in the icecore data are from short term variability and likely reflect regional variation rather than global variation.  Applying a smooth to the data would make the modern temperatures stand out still further.

    Clearly Moore's argument that modern temperatures are not unusual is fatally flawed.

    His argument that it is not CO2 consists, as near as I can make out, solely in citing Spencer and then pointing out that sourcewatch does not link to any rebutals.  Sourcewatch is, of course, a website solely devoted to listing institutional and financial connections of various sources of information.  It is not part of the ambition of source watch to survey scientific research and rebut particular arguments.  Moore has only looked for rebutals to Spencer's claims were we can be confident he would not find them.  Had he looked at Skeptical Science, however, he would have been more than satisfied.  In particular he would have found a direct rebutal of Spencer's claims about climate sensitivity.  By limiting his search, however, Moore gets to falsely pretend that there is no such rebutal available, avoids the need to rebut the rebutals, and gets the falsely play the ad hominen card as well.  Not a bad return for being, at best, a slovenly researcher. 

    Finally, Moore finishes with a conspiracy theory which is not worth commenting on, but certainly makes an interesting point about his intellectual credibility.

  30. I scanned to find a remark on this issue in the comments, but so far haven't seen any.  Unless I'm mis-reading something, in the advanced version of this article, the graph labeled thus:

    "Figure 9: TOA Radiation (Trenberth 2009)"

    Should actually be:

    "Figure 1c from Hansen et al (2005) "Earth’s Energy Imbalance: Confirmation and Implications".

    The caption for Figure 1 in that paper runs as follows:-

    Fig. 1. (A) Forcings used to drive global climate simulations. (B) Simulated and observed temperature change. Before 1900, the observed curve is based on observations at meteorological stations and the model is sampled at the same points, whereas after 1900 the observations include sea surface temperatures for the ocean area, and the model is the true global mean. (C) Net radiation at the top of the atmosphere in the climate simulations. Five climate simulations are carried out that differ only in initial conditions.

    This information was provided to me by MA Rodger in another thread.

  31. Further to #80.

    There is no Figure 9 in the Trenberth et al (2009) as linked in the advanced level rebuttal. There is a Figure 9 in Treberth et al (2013) "Earth's Energy Imbalance." This figure (presently eluding me on line) plots but a wiggly line 2000-to date showing incoming, outgoing and net radiation, this last compared with El Nino. So the important bit of that Figure 9 is the net value as per the graph below (as shown at the SkS post that this discussion initially began) but with a more recent wobble added on to the end of the trace.

    Trenberth figure

    Sadly dvaytw, there is no "clincher" here as the data only starts in 2000. (Mind, OHC does a good job of clinching the "AGW has paused" delusion.)

    Which brings me to a follow-on. If the Hansen Figure 1C uses OHC to 'create' a graph 1880-date as could be interpreted from the advanced level post, is that any more strange than Trenberth using satellite data to 'create' such a graph - both are achronistical. Of course Hansen et al uses land temperature for the earliest part of his analysis and adds in SST there after (as the caption says). Trenberth et al (2013) presents a similar graph 1850-to-date (their Figure 1) and both papers then compare these results with OHC data.

  32. MA Rodger I think some of what you're responding to here is brought up in a question I asked in Trenberth on Tracking Earth’s Energy . In any case, thank you.  

    A follow-up question: so am I correct in understanding that Trenberth and Hansen are using temperature data to calculate the energy balance at the TOA prior to satellite data?  

    And is there a way to explain the verified energy imbalance, other than the GHE?  

    Finally, I recall reading the criticism that the margin of error for Trenberth's TOA data is very large.  Is this a legitimate criticism?

    (Note to moderator: this comment and the one above it may fit more appropriately in the discussion under the "Trenberth on Tracking Earth's Energy" article. )

  33. dvaytw - I am struggling a little to follow you. Can you please be more precise about which paper you mean where you find Trenberth and Hansen discussing TOA energy balance at times prior to the satellite era? In Trenberth et al 2013, there is discussion of how difficult this is given the uncertainity in OHC measurements prior to Argo.

  34. scaddenp @83.

    The papers under discussion are Trenberth et al 2013 & Hansen et al 2003, both of which calculate the ERB from back in the 19th century having modelled the climate to fit temperature records. T(2013) figure 1 and H(2003) figure 1c are graphs of this, the latter being figure 9 of the 'advanced' post here but which is mis-referenced.

  35. @82, 83 and 84

    I think I understand the importance of Trenberth's satellite data now; it lies not in the amount of increase since the satellites went up (as this was very recent), but in that it matches predictions made with OHC data.  Have I got that right?

    I also have a question about Evans 2006: he states there that Greenhouse radiation has increased by about 3 W/m2 since pre-industrial times, and a denier pointed out that this matches pretty much exactly the increase in TSI since that time:

    Solar Irradiance Since 1660

    I realize there are plenty of reasons we know it's not the sun and have pointed them out to him, but am wondering if there is any comment to be made about this correlation.

    PS the discussion is happening in the comments here, if anyone's interested:

    How to Talk to a Climate Denier

  36. dvaytw @85.

    Regarding Trenberth's ERB from CERES, it does suffer massively from calibration issues. Its decadal value is more an inference relying on OHC data than a result in itself. IPCC AR5 Chapter 2 Section 2.3.1 is saying the net satellite measurements are 'calibrated' +/-2 W/m2, which is rather a lot. There is also quite big trend calibration issue (tenths of W/m2 per decade) for which a reference doesn't immediately spring into hand.

    What we importantly do have with ERB measurements is sight of the general wobbles which are valuable checks on GCM results. This also allows gaps to be filled in that allow demonstration that some of the crackpot wobblology theories (Staduim Waves etc) are nonsense and cannot be happening due to what we know of ERB. That sort of answers some of your second question @82 and is a bit of background to a graphic of mine that shows ERB less smoothed than normal (here - usually two clicks to 'download your attachment'). Unsmoothed it can be seen how any trend in ERB has yet to emerge from the wobbles.


    Your TSI graph comes from Lean(2000) (Data here @ NCDC). More recent assessments of historical of TSI  (see graph from CU here) do not yield such a large rise since the seventeenth century. And also, ΔTSI has to be divided by 4 to be equivilant to climate forcing as TSI is measured over the disc and forcing over the sphere. Perhaps one thing to remember with this TSI calibration here is that TSI is a component of the ERB measurement and its 'calibration' has been revised by quite a bit recently, usually downwards, much to the annoyance of denialists.

    Positive forcing is now above 3W/M2 (AR5 table A.II 1.2 gives positive forcing of +3.4 W/m2 for 1750-2011and it is rising at about 0.04 W/m2 pa). But there are also less-well defined negative forcings yielding a net anthropogenic forcing of ~+2.3W/m2 for 1750-2011 according to AR5 A.II.

  37. One number I forgot to tap in @86; AR5 A.II gives an average solar forcing over solar cycle 23 (1996-2007) of 0.045W/m2.

  38. In addition to MA Rodger's point that the change in TSI needs to be divided by 4 to account for the disk vs. sphere question, you also have to multiply the value by 0.7 to account for the fact that the earth's albedo averages about 30%. It's the change in absorbed solar that needs to be compared to the greenhouse forcings, not the change in received solar.

  39. Thanks fellows for the info.  May I know a good source for a novice's understanding of the "disk vs. sphere question"?

  40. dvaytw @89

    Imagine the Earth as a dinner plate, which as it rotates around the Sun always presenting its "face" towards the Sun. The surface area that the Sun irradiates is pi * r**2 where r = radius of the "earth". The "back" side is never irradiated.

    Now imagine that the plate is replaced by a ball of the same radius; the surface area has consequently increased. If the ball is not rotating on its own axis, then the surface area that the Sun irradiates is 2 * pi * r ** 2 (the surface area of a hemisphere). If the ball does rotate then (over the period of rotation) then each hemisphere spends half the time irradiated and half the time is dark. So the total area irradiated = 4 * pi * r**2.

    So the factor by which the Suns irradiance is diluted by the fact that the Earth is a rotating sphere, rather than a static diskworld is

    4*pi*r**2/(pi*r**2) = 4

  41. dvaytv:

    To completely muddle Phil's explanation, you need to keep in mind that the sun's rays (at the mean earth-sun distance) are measured at a right angle to the parallel beams. When those rays fall on a surface that is not at a right angle, the intensity is reduced. The mathematics of this is straightforward - the intensity is reduced by sin(angle) [when an angle of 90 is used for the case where the sun's rays are at a right angle to the surface, and 0 for the surface being parallel to the sun's rays].

    To get a 24-hr total for the entire earth, you could then calculate the intensity for each point on the surface (including the dark side) for every time of day - accounting for the sun angle and its effect in intensity-  and then integrate (sum) over the entire globe and day.

    And then, after doing all that, you'd realize that the ratio is 4, and it would dawn on you that the size of the shadow cast by the earth is pi*r^2 and it doesn't matter whether the earth is a disk, or a sphere, or a cone, or any other shape. The size of the shadow tells you how much sunlight it intercepted. For emissions, the shape of the earth does matter, and a sphere is a close approximation.

    It's sort of like the joke about the mathematician, who was asked to solve the following:

    Two trains are 120km apart, travelling towards each other at 60km an hour. A really fast bird travelling at 120 km/hr takes off from one and flies to the other, then instantaneously turns around and flies back, repeating until the two trains meet. When the trains meet, how far has the bird travelled?

    The mathematician quickly says "120 km". The fellow posing the questions says"

    "That's right. You know, a lot of mathematicians try to answer that by solving for each successive the time and place that the bird reaches a train and turns around, and then integrating the infinite series over time to get the total. I see you took the fast solution."

    The mathematician says:

    "There is a faster way?"

    [The trains travel for one hour until they meet. The bird travels 120 km in one hour.]

  42. dvaytw @89, first Phil's response is correct, and needs no further addition unless you want to get into the minutia of insolation at particular latitudes at particular times of day.

    Second, Bob Loblaw's resonse is also correct, but may confuse at first blush given that insolation is normally calculated at given points using the zenith angle and latitude, such that at noon on the equator on the equinox (and thus ignoring seasons), the angle used is 0 degrees, and consequently the cosine rather than the sine is used:

    The formula for declination, to partly take seasons into account is:

    δ =23.45*cos(2*π*(JD-172)/365)

    To fully take seasons into account, you also need to take into accoun the variations in the Sun/Earth distance.  A partial formula for that, plus additional details can be found here.

    In the end, daily insolation at the top of the atmosphere, ploted for latitude and time of year looks like this:

    The very high summer insolation at the poles surprises most people at first glance, but is due to having 24 hours rather than a mere 12 hours insolation.

    Needless to say, this is too much information for most uses, and we can resort back to the annual average figure as calculated by Phil.  Needless to say, however, climate models integrate everything based on their smallest time step (typically one to three hours, I believe).  I mention that because I have seen a number of "skeptical" arguments based on assuming that climate models use the same simplifying assumptions used in simplified explanation (as if they use no physics more complex than taught in grade six).

  43. ryland (from another thread), you should read Michael Tobis's explanation of how the IPCC's explanation of attribution usually is mis-spun or even dis-spun by the media, and in particular by Curry.

  44. Excellent dynamic graphic at Bloomberg, showing natural versus anthropogenic forcings.

  45. That is an excellent graphic!  Have to remember that for class.  Thanks Tom D.

  46. Perhaps it is a while since these pages were updated?

    In the sections above which discuss the radiation spectra evidence, the links to the following papers do not work: Griggs 2004, Chen 2007, Philipona 2004, Wang 2009, Evans 2006.

    Perhaps an investigation into why these links are failing is in order. Is it possible to provide more durable links? Would a more complete bibliographical reference would be a good idea?

  47. Harries 2001

    Griggs 2004

    Philipona 2004

    Evans 2006

    Chen 2007

    Wang 2009

  48. I am engaged in developing and delivering training courses on AGW to teens and senior citizens in the Washington D.C. area. I find useful text and graphics in all three levels (basic, intermediate and advanced) of this post. Great job!

    What would be good is a credible and scrutable discussion and graphic presentation of how the various forcing factors affected the global temperature since 1910; i.e. the steady increase from 1910 to 1940, followed by the slight downward trend from 1940 to 1975, followed by the sharp increase from 1975 to the present. Citing model calculations is useful, but skeptics have done a good job of casting doubt on the credibility of models, and models sound like black-box mumbo-jumbo to a non-technical audience.

    A more understandable story emerges if you just examine the trends in sunlight, GHGs and aerosols and relate them to the shape of the curve. Your post does some of that, and I plan to use the insights from it. In addition, I have looked at the graphs of trends in GHGs, aerosols and sunlight since 1910, and I can tell a pretty good qualitative story. But has anyone done a simple quantitative analysis to try and reproduce the shape of the temperature curve?

    From the reading I have done, there appears to be some good analysis of the sensitivities of global temperature to changes in GHGs, aerosols and incident sunlight. Has anyone with access to all the basic data simply multiplied the sensitivity times the amount of change for each of these factors and summed them up for each year since 1910? Would an analysis like that produce something that looks even vaguely like the temperature curve? Is it necessary to include other factors? Or is it a futile exercise?

    Thanks for the great work you are doing to keep this issue in front of the public.

  49. richieb1234--Bloomberg Businessweek (of all places!) had a really good look at this a few years ago: What's Really Warming the World which is based on NASA-GISS modelling.

  50. richieb1234 @98,

    The basic problem you face trying to simply show a tight correlation between forcing & temperature is the impact of large short-term changes in climate forcing caused by volcanoes superimposed on the slower changes in climate forcing, as shown here in IPCC AR5 Fig 8-18. (The numbers are available in AR5 AII table 1.2.)

    IPCC AR5 Fig 8.18

    Because of these more dynamic changes, I have found the task involves far more than forcing and sensitivity. Even using a simple Climate Response Function (the timed progression of a warming resulting from a forcing based on the sensitivity - see for instance Hansen et al (2011) who discuss these at some length.) doesn't overcome the problem. You would end up having to set up what is undeniably a model to convert forcing into the resulting global temperature change. (I would add here that in 1910 the climate system was far from in-balance and so 1910 is not a good date to begin such modelling.) And for such a model not to be actually emprirically-based, you would probably end up with a full GCM model whose credibility has, as you say, been criticised by climate denialists.

    This is what is being shown in the link @99. But I would ask if you need the modelling to present the message that the climate forcing of recent times forcing is overwhelmingly anthropogenic with the only significant effect from natural forcing being those short-term volcanic forcings. If the forcings are overwhelmingly anthropogenic, it is surely difficult to argue that it is not the same for the warming.

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