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CO2 is main driver of climate change

What the science says...

Select a level... Basic Intermediate

While there are many drivers of climate, CO2 is the most dominant radiative forcing and is increasing faster than any other forcing.

Climate Myth...

CO2 is not the only driver of climate

CO2 is not the only driver of climate. There are a myriad of other radiative forcings that affect the planet's energy imbalance. Volcanoes, solar variations, clouds, methane, aerosols - these all change the way energy enters and/or leaves our climate.

Understanding what drives climate does not occur by a process of elimination. It's happens by a process of integration. There are many influences of climate that all need to be considered together to gain the full picture. The following lists the radiative forcing, loosely defined as the change in net energy flow at the top of the atmosphere, from the various factors that affect climate (IPCC AR4 Section 2.1). Positive radiative forcing has a warming effect (so obviously, negative radiative forcing has a cooling effect).

  • Surface Albedo has changed due to activity such as deforestation. This increases the Earth's albedo - the planet's surface is more reflective. Consequently, more sunlight is reflected directly back into space, giving a cooling effect of -0.2 Wm-2.
  • Ozone affects the climate in two ways. The depletion of stratospheric ozone is estimated to have had a cooling effect of -0.05 Wm-2. Increasing tropospheric ozone has had a warming effect of +0.35 Wm-2.
  • Solar variations affect climate in various ways. The change in incoming Total Solar Irradiance (TSI) has a direct radiative forcing. There is an indirect effect from UV light which modifies the stratosphere. The radiative forcing from solar variations since pre-industrial times is estimated at +0.12 Wm-2. Note that the radiative forcing from solar variations may be amplified by a possible link between galactic cosmic rays and clouds. However, considering the sun has shown a slight cooling trend over the last 30 years, an amplified forcing from solar variations would mean a greater cooling effect on global temperatures during the modern warming trend over the last 35 years.
  • Volcanoes send sulfate aerosols into the stratosphere. These reflect sunlight, cooling the earth. A strong volcanic eruption can have a radiative forcing effect of up to -3 Wm-2. However, the effect of volcanic activity is transitory - over several years, the aerosols wash out of the atmosphere and any long term forcing is removed.
  • Aerosols have two effects on climate. They have a direct cooling effect by reflecting sunlight - this is calculated from observations to be -0.5 Wm-2. They also have an indirect effect by affecting the formation of clouds which in turn affect the Earth's albedo. The trend in cloud cover is one of increasing albedo which means a cooling effect of -0.7 Wm-2.
  • Stratospheric Water Vapour has increased due to oxidation of methane and had a slight warming effect of +0.07 Wm-2.
  • Linear Contrails from aviation have a slight warming effect of +0.01 Wm-2.
  • Nitrous Oxide reached a concentration of 319ppb in 2005. As a greenhouse gas, this contributes warming of  +0.16 Wm-2.
  • Halocarbons (eg - CFC's) were used extensively in refrigeration and other industrial processes before they were found to cause stratospheric ozone depletion. As a greenhouse gas, they cause warming of +0.337 Wm-2.
  • Methane is actually a more potent greenhouse gas than CO2. Pre-industrial methane levels, determined from ice core measurements, were around 715 parts per billion (ppb). Currently methane rates are at 1774 ppb (eg - 1.774 parts per million). The radiative forcing from methane is +0.48 Wm-2.
  • CO2 levels have increased from around 280 parts per million (ppm) in pre-industrial times to 384 ppm in 2009. The radiative forcing from CO2 is +1.66 Wm-2. CO2 forcing is also increasing at a rate greater than any decade since 1750.

Here's a visual summary of the various radiative forcings:

Figure 1: Global mean radiative. Anthropogenic RFs and the natural direct solar RF are shown. (IPCC AR4 Section 2.1)

Putting it all together, Figure 2 compares the warming from human caused greenhouse gases to the total radiative forcing from all human sources.

Figure 2: Probability distribution functions (PDFs) from combining anthropogenic radiative forcings. Three cases are shown: the total of all anthropogenic radiative forcings (block filled red curve); Long-lived greenhouse gases and ozone radiative forcings (dashed red curve); and aerosol direct and cloud albedo radiative forcings (dashed blue curve). Surface albedo, contrails and stratospheric water vapour RFs are included in the total curve but not in the others. Natural radiative forcings (solar and volcanic) are not included in these three PDFs. (IPCC AR4 Figure 2.20b)

Greenhouse gases and ozone contribute warming of +2.9 Wm-2. The majority of this is from CO2 (+1.66 Wm-2). This warming is offset by anthropogenic aerosols, reducing the total human caused warming to 1.6 Wm-2. So the warming from CO2 actually exceeds the final total radiative forcing. The other important point to glean from Figure 2 is that we have a relatively high understanding of greenhouse gas radiative forcing. The probability density function (PDF) shows a much higher probability than the aerosols PDF, meaning the uncertainty associated with greenhouse gas forcing is much lower. This is also confirmed by experimental observations from both satellites and surface measurements which confirm the enhanced greenhouse effect from rising greenhouse gases.

So in summary, there are two reasons for the focus on CO2:


  • CO2 is the most dominant radiative forcing
  • CO2 radiative forcing is increasing faster than any other forcing

Intermediate rebuttal written by John Cook

Update July 2015:

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

Last updated on 15 July 2015 by pattimer. 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.


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Comments 1 to 50 out of 69:

  1. cleanwater, you forgot to mention Ångström! It's a pitty. Apart from your random quotes and some standard shouting, you're welcome to discuss science, if you'll ever will. P.S. much too easy to copy and paste to leave garbage around ;)
  2. A great addition to this page would be a link to the page with the evolution of relative forcings over the past century or so. I just can't find that page at the moment.
    Response: Good idea. I may reshape the content to include the graph you're talking about but in the meantime, here it is:

    Separate global climate forcings relative to their 1880 values (GISS).
  3. Hot off the press from the Journal of Climate. Cloud data supports the higher end of the estimates of climate sensitivity :-/
  4. In the rediative forcing graph it shows "well-mixed greenhouse gases".  Is there a breakout of CO2, H2O, methane etc to show the relative importanct to the effect?

    and a related question, when we burn a fuel we get CO2 and H2O in a 3:4 ratio (typical). Since H2O is a more potent green house gas why all the hupla on CO2 and not the incresed H2O?


    [TD] Water vapor's concentration in the atmosphere is limited by temperature.  Putting more water vapor into the air than the air's temperature will support causes the excess water to drop out in about 10 days.  Therefore water vapor is a feedback to temperature increase, not a forcing.  See the rebuttal to the myth Water Vapor is the Most Powerful Greenhouse Gas.

  5. roosaw...  Here's the RF chart from IPCC AR5 that has them broken out...

  6. Reply to likeithot from here.

    Thank you for responding. Now what climate science actually states is that climate will respond to the net effect of all forcings. A huge amount of climate science also goes into understanding the internal variability that is inevitable when you unevenly heat an ocean-covered planet. Unfortunately, important processes (especially ENSO) for determining surface temperature defy predictive modelling. So, to quote the modellers - "climate models have no skill at decadal level prediction".

    Given these constraints, and the multiple forcings at work in climate, what then do you think the data should like that would convince you that the attribution to CO2 is accurate?

    If you are stumped, then perhaps you should read the IPCC WG1 chapter on attribution to see the approaches that have been done so far.

    One very important consideration to think about is that while surface temperature has a very high degree of variability, you do expect total ocean heat content to vary a great deal less in response to a constant forcing.

    And as an aside, if you dont want to have your comment moderated, then try reading and complying with the comments policy. If you want to bluster with uninformed rhetoric, then there plenty of sites on the internet that will welcome your comments. If you want to discuss the science, then welcome, and please study what the science says so we can have an informed discussion.

  7. likeithot wrote: "...for me to "believe" in AGW there would have to be a clear correlation between the beginning of human CO2 emissions and evidence of warming."

    Um, there is a clear correlation between the beginning of human CO2 emissions and evidence of warming... so long as you are looking at the full picture.

    If you look at the five minutes after the first coal power plant went online, no you won't see any correlation. Nor is it clear for the first decade or two. However, look at CO2 levels and temperature levels for the first hundred years since the industrial revolution and there is a very clear correlation. Both have gone nearly straight up at rates faster than anything seen previously in century level resolution proxy data.

    Thus, this argument amounts to, 'I will cherry pick a time frame too short to see the correlation and then pretend it is not happening'.

  8. Greetings - I'm new to this webpage / forum, which I find fascinating. The brief bio's on the Skeptical Science Team is as impressive as it is varied. I realize this is an old thread, but it looks like a good place to start.

    Let me say at the outset I agree the climate is changing - warming in most areas of the globe - with a net temperature increase. That is obvious in the data, of which I spent a 40 year career collecting, analyzing and processing. Living in the plains, the changes are apparent - latter first snows, earlier spring, increases in non-native insects, plant and human diseases; the list goes on.

    While I have my own understanding and response to Change skeptics, I've learned to consider all the facts. Science is after all based in question,  discovery, hypothesis, observation, proof, testing proof. Therefore I have two questions.

    1) Water Vapor and it's impact on the changing climate. Per the older NASA article from November 2008

    and others since, it seems H2O is somewhat downplayed. What is the Teams sense on H2O impacts on climate change?

    2) Science by concensus (Bill Nye's famous videos). Other disciplines outside of meteorology have differing views on the changing climate. By education I was a Soil Science major. In my 'weather' career I've seen this lack of cross discipline discussion result in all manner of issues. Again, what is the Teams sense on "Science by concensus" versus the time tested steps of the Scientific Method?

    Thank you. I look forward to your response.

  9. While some threads are dated, no threads are dead here.

    Water vapor is best addressed on this SkS thread here:

    Explaining how the water vapor greenhouse effect works

    I have placed a followup to your question there.  Any questions you may have after reading the post and my response should be placed there.

    Many other threads deal with consensus.  The Search function will find many; pick one and re-ask your question there.

  10. ClimateTool - Regarding consensus, I would suggest following Daniels excellent suggestion, and looking at threads using the Search box on the upper left.

  11. ClimateTool, in addition to the posts pointing you to other sections of the site, short answers to your questions are;

    1: The amount of water vapor the atmosphere can hold is directly tied to atmospheric temperature (e.g. "relative humidity" is the amount of water vapor in the air relative to the maximum amount possible for the current temperature). Thus, temperature increases from CO2 will lead to more water vapor... and corresponding additional warming. Thus, water vapor is a significant positive feedback in global warming, but cannot 'initiate' the warming itself.

    2: Your question itself contains a fallacy. There is no conflict between, "'Science by consensus' versus the time tested steps of the Scientific Method". There is concensus on AGW because application of the scientific method over the course of the past 100+ years (since Arrhenius proposed the AGW theory in 1896) has overwhelmingly shown it to be accurate. Nor is there any "lack of cross discipline discussion". Oceanographers, botanists, zoologists, astronomers (studying atmospheres on other planets), and scientists in various other fields have all independently found evidence matching what climatologists have shown.

  12. ClimateTool, I'm going to expand a little on CBDunkerson's second point.  The lack of cross-discipline discussion is a complaint I often hear from people in genuine doubt and from fake skeptics.  The complaint is a sure sign that the writer or speaker hasn't engaged the science in any meaningful way.  After all, if one wants to know what the relevant science says, but doesn't want to wade through tens of thousands of publications, all one has to do is go to a summary of the existing relevant science.  

    That's what the IPCC AR5 is.  It's a summary of the relevant science.  It was written by ~850 scientists, regular publishers in their disciplines, who were not paid for their work.  It directly references 20,000+ publications, and tens of thousands more by proxy.  It went through multiple rounds of peer review that generated 150,000+ comments.

    You complain that little cross-discipline discussion takes place, but the second section of AR5 (Working Group 2: Impacts, Adaptation and Vulnerability) is nothing but cross-discipline collaboration to summarize thousands of interdisciplinary studies.  I don't mean to suggest that the other WGs are not interdisciplinary, for they are, but WG2 is obviously so.

    And (speaking to your other complaint about consensus) the IPCC assessment reports represent the consensus of evidence.  If you are serious about understanding the problem, the well-organized AR5 is the place to start.  SkS welcomes both questions and informed discussion.

  13. ClimateTool - One side note: your use of the capitalization in "...what is the Teams sense..." is often a shibboleth of pseudo-skeptics; tied to conspiracy theories that have a 'Team' of scientists somehow organized to deceive everyone else, usually for some vague sort of world domination. 

    Which is silly - organizing scientists across multiple fields, countries, and decades to argue against the facts would be like herding ADHD cats. Just not possible.

    If you are actually interested in the topic of climate change, and (particularly for this site) various myths about it, I would suggest avoiding terminology with implied insults.   

  14. "..organizing scientists across multiple fields, countries, and decades to argue against the facts would be like herding ADHD cats."

    I would add "...away from a field of open tuna cans."  Such an effort would be asking those scientifickyADHD cats to sacrifice their own professional self interest.

    Why would they not chose to make a name for them selves by picking low hanging fruit and bucking an obviously false paradigm?  Makes no sense.

  15. KR

    My apologies - I meant no such thing. My goal was to ask for the concensus of the team members as listed in the "About" section. I shall avoid such faux pas in the future.

    I do argue however that organizing various disciplines does occur on a regular basis. Having been involved in both operational and field level research I have been fortunate enough to work with geologists, physicists and agronomists on Climate Change issues.

    Perhaps my naivete is showing through. But I stand by my ascertion.

    Thank you for your responses.


    [DB] "concensus of the team members"

    While consensus is important, what really matters is what the evidence itself shows. Consensus of opinion does not replace evidence and physics.

    If you have questions on the evidence and the physics of the science, please use the Search tool to find the most appropriate thread on which to place them (after reading it and the comment thread underneath the article).  Thanks!

  16. ClimateTool - Ah, that makes sense; perhaps asking what the "SkS team" is thinking would be a less ambiguous terminology.

    However, I'm a bit confused as to what assertion you are standing by? You've just asked a couple of questions...

  17. Climate Tool:

    As was pointed out upthread, the IPCC reports, and various others, are compendia of cross discipline results.  Your suggestion that cross discipline analysis is not done in AGW is simply false.  Please cite a major summary report that does not contain results from multiple disciplines.

    The SkS team has a variety of opinions, often different.  You should be more specific in your question.  About water vapor specificly, which appears to be your question, without asking I dare say everyone agrees H2O is an important greenhouse gas.  It contributes a large fraction, or a majority of the greenhouse effect.  Everyone knows this.  

    Water vapor concentration is dependent on the CO2 concentration.  CO2 is not dependent on water vapor.  This means CO2 is the temperature control knob.  Future temperature changes (and water vapor changes) will follow the CO2 changes.

  18. Just to simplify a little here...

    CO2 is a long-lived, non-condensing greenhouse gas that is well mixed from pole-to-pole and through the full column of the atmosphere.

    H2O is a short-lived, condensing greenhouse gas that freezes out at higher latitudes and altitudes.

  19. If the unremitting rise of CO2 from industriail activities is the dominant factor, why did the global temperature decrease from 1940 to 1970?

  20. ..aerosols !

  21. Ken Kimura @19, if you sum all forcings (ie, not just that from CO2) using the values estimated by Meinhausen et al (2011), the trend in the forcings from 1940 to 1970 is 0.0003 +/- 0.0007 W/m^2 per annum.  That is, it is essentially zero, and may well have been negative.  On top of that, there was a substantial El Nino early in the sequence and a La Nina following the volcanic eruption in 1965 which together with the very low trend in forcings may have tipped the temperature record negative.

    Having said that, if you look at this model of the ENSO adjusted temperature responce to forcings, you will see to large temperature spikes around 1939 and 1945 that are not accounted for by the model and which also contribute to the negative slope.  It is difficult to know that to attribute those spikes to.  They may be due to unusually large forcing by Black Carbon during World War 2.  They may also be due to an artifact in the temperature record due to the sudden, very large reductions in temperature coverage along with the simultaneious large changes in methods of measuring Sea Surface Temperature brought about by WW2.

    What they are not due to is the Pacific Multidecadal Oscillation (which is captured by the ENSO signal) or the Atlantic Multidecadal Oscillation (which does not have a suitable pattern to explain the phenomenon).  Nor are they due to a fundamental misunderstanding of the forcings, or the relative effects of natural and anthropogenic forcings.  The model I linked to allows you to weight the various forcings, making natural forcings much stronger in effect than anthropogenic forcings if you desire.  Any such attempt, however, greatly increases the number of temperature discrepancies.  That fact shows conclusively that theories that attempt to explain the twentieth century temperature record without anthropogenic factors being the dominant factor post 1940 (and a significant factor prior to 1940) are doomed to failure. 

  22. Tom Curtis@21,
    According to the figure 5 of the following page, stratospheric and reflective tropospheric aerosols were major negative forces during the period.
    What do you think the main cause of those aerosols was?
    If it was due to the industrialization, you know that the industrialization started long before 1940.

  23. Ken Kimura @22, I discuss the trend from 1940-1970 because you asked a question about the trend from 1940-1970, and for no other reason.  For you to then turn around and ask "you know that the industrialization started long before 1940" looks like a calculated, and hypocritical insult.

    With regard to your former question, stratospheric aerosols are almost exclusively from volcanic erruptions.  Tropospheric aerosols are from a combination of wind born sea salt, refractory compounds from forest, desert sand and anthropogenic factors.  Forcings, however, represent the change in a factor over time, and the vast majority of the change in tropospheric aerosol load is from anthropogenic factors - primarily from sulfur in coal and oil.  As can be seen from this graph from the IPCC AR5, the combined anthropogenic effect (red line) from 1940-1970 results in a positive slope in forcing:

    The combined anthropogenic plus natural forcing is flat or negative due to the lack of volcanic erruptions from about 1915 and the onset of a large eruption (Agung, 1963-4) along with a number of smaller eruptions.

    Note that the above graph sets the zero point for forcings at 1750 rather than the 1880 used in the GISS forcing graph you pointed to, and the Meinhausen 2011 forcings displayed in the model to which I linked.

    With regard to the relation between anthropogenic GHG forcings and anthropogenic aerosol forcings, initially the aerosol forcing from oil and (particularly) coal dominate in the short term, but with steady state use the GHG forcing comes to dominate very quickly.  That is because the initially dominant aerosol load is quickly washed out of the atmosphere by rain, while the GHG concentration (particularly CO2) accumulates.  With accelerating coal combustion, these factors can approximately balance for a while, as can be seen from 1750-1860 above, but in the 20th century the GHG forcing has been stronger both because of the accumulation of CO2 in the atmosphere and a gradual switch to cleaner (ie, less sulphur content) fuels.

  24. Tom Curtis @23.

    "For you to then turn around and ask "you know that the industrialization started long before 1940" looks like a calculated, and hypocritical insult."
    I had no intention to insult you.
    And I have no idea why you thought so.

    "With regard to your former question, stratospheric aerosols are almost exclusively from volcanic erruptions."
    I have at least 3 questions.
    1) What are the evidences of this claim of yours?
    2) How did they measure the stratospheric aerosol density during the period?
    3) How can you be sure that their mesurement was accurate?

  25. Ken Kimura @24 , let me be quick to assure you that Tom Curtis was not the only one to see your: ". . . started long before 1940" comment as insulting (or something very close to that).

    Perhaps you didn't mean it that way . . . or only meant it at some subconscious level . . . or at another level, meant it disingenuously.  Or all three ways at once [such is the complexity & inconsistency of the human mind] .  But your comments had a general background context or "tenor" which would lead Tom to his conclusion quite naturally and automatically,  I do believe.

    Aerosol reflectivity can be measured from ground stations; and in more recent decades from satellite observations; and measured indirectly by correlation with the observed changes after each significant volcanic eruption. [Instrumental measurement or proxy measurement]

    For the accuracy of the measurements & estimations, you might care to consult the original scientific papers that investigated such phenomena.  But, unless you have good reason to doubt their bona fides [in which case you should declare your hand : and show the evidence you rely on for such opinion] . . . then your question is a side-issue, which need not distract us from the main thrust of your inquiry.

  26. Ken Kimura @24, anthropogenic aerosols are well known because the types and quantities of fuels burnt in various countries are well known, and so the production levels are known.  Similarly, for volcanic aerosols, the size, force and duration of volcanic activity is also known, given an approximate indication of volcanic aerosol production.  More importantly, aerosols are found in ice cores from Greenland, Antarctica, the Rockies, Andes and Himalayas, and also from Mount Kilimanjaro and (I believe) Mount Kenya from tropical Africa.  The aerosol density at different levels in the ice cores can be compared to equivalent density levels in recent cores, which are then correlated with satellite measurements of aerosol optical depth.  Combined, these give a reasonable though not perfect measure of aerosol optical depth going back hundreds of years.

  27. Ken Kimura @24.

    I find your comments curious, extending as they do initially beyond this thread. Note here @24 you say you intend a couteous enquiry and see nothing to suggest you are not doing so. This is followed by a set of questions that imply you consider the person you address to be, if not sincere, not to be trusted. "...this claim of yours." "How can you be sure..."

    The science being discussed here is not anybody's personal property. Scientific knowledge is open access thus owned by all. That is what makes it so powerful. (Having written this, I am conscious that I now embark on addressing questions that do have ownership and with answers that have a single author and so could be wholly disowned elsewhere.)

    Picking up a word in your questioning @24, "How did they measure the stratospheric aerosol density during the period?", you might find Sato et al 1993 a worthwhile read (PDF here). This paper predates the appearance of the ice core data which has allowed the record to be extended back before 1883 with far greater confidence and accuracy.

    Further, I am mindful that there may be a not-uncommon misconception buried within your various questions. You perhaps are of the view that early indstrialistaion was entirely driven by fossil fuel use, initially exclusively coal, and if this were so would we not have had from its earlierst times CO2 emissions & SO2 emissions in a constant proportion (until SO2 pollution was reduced in the 1970s). However, the contribution of mankind's rising CO2 emissions from burgeoning coal use only overtook the mounting emissions from low SO2-emitting wood burning in the 1910s, apparently. (CDIAC FF data & CDIAC LOC data.)

    Perhaps for completeness, I should add that the forcing from GHGs in those early decades is often dismissed as too small to have significantly affected global temperatures pre-1940. Yet, if you examine the rise of atmospheric CO2 since pre-industrial times (IPCC AR5 data to 2011here), 27% of today's atmospheric CO2 rise causing 31% of today's CO2 forcings were present by 1940. And with their slower increase, the temperature response would likely be closer to 40% of today's total. But saying that we should be sure not to forget "CO2 is not the only driver of climate."

  28. billev

    Following on from the previous post here.

    This topic is about the other driving factors behind climate so worth reading first. 

    Firstly, a smaller point, the rise in the earths heat content may not be monotonic because there is a seasonal cycle. The earth absorbs more sunlight during the southern hemisphere summer when the darker (all that ocean) southern hemisphere is pointed more towards the sun This seasonal cycle may be large enough to overwhwlm the warming from CO2 etc for a year or so, thus on a seasonal scale the rise may not be monotonic. However the rise in total heat content should be roughly monotonic on timescales of multiple years.

    Then there is another assumption you are making that isn't correct. You are assuming that the temperature change, thus the heat accumulation, will all happen in the atmosphere and that thus the atmospheric temperature should rise nearly monotonically. However less than 2% of the aded heat is going into the atmosphere; most, around 93%, is going into the oceans.

    At the same time there are internal energy transfers that occur between the atmosphere and the oceans and since the oceans have hugely more thermal mass than the atmosphere a small flow from the oceans to the air, relative to the heat capacity of the oceans, can constitute a significant change in temperature for the atmosphere. As a result, atmospheric temperatures are a very 'noisy' signal; variations due to this internal variability can mask any underlying trend for significant periods, and the resulting temperature rise, of the air, won't be monotonic. The standard timescale defined by the World Meteorological Organisation to be used to detect climate changes in the atmosphere is 30 years. Running averages over 30 years or so should show roughly monotonic change. Anything on significantly shorter timescales would be more fortuitous, depending on the vagaries of internal variability.

    There is another approach. Since most of the extra heat is going into the oceans, we would expect the heat increase there to be roughly monotonic. And it is.

    This is the heat increase of the top 2000 meters of the ocean, which is a bit over half its volume. Apart from a seasonal signal you can see it is quite monotonic. A few dips associated with volcanic eruptions in 1982 and 1992, and a dip around the time of the big El Nino in 1998. Also some variation during the 60's but instrument coverage back then wasn't very good and there was likely some significant aerosol cooling before the various Clean Air Acts started clearing up air pollution. But since then, broadly, it is very monotonic. And in fact, the rate of heating is increasing, which is what we would expect with CO2 levels rising.

  29. Glenn's post immediately above this one is in response to several comments by billev over on this thread. In billev's last comment, he said:

    If the CO2 caused energy imbalance is the reason for the Earth's temperature rise then that temperature rise should be continuous like the steady, and accelerating, rise of CO2 in the atmosphere.

    I am wondering, billev, just exactly what you would accept as convincing evidence that CO2 is having an effect. From the statment quoted above, it would appear that you want to see no variation from a continuous rise in temperature. That is a suprising expectation, because for it to be true, then rising CO2 would have to have two effects:

    1. It would have to have an effect that causes an increase in global surface temperature.
    2. It would have to have an effect that prevents any other known causal factors from also affecting temperatures over the period in question. That would mean:
    • reductions/increases is solar radiation could no longer cause reductions/increases in temperatures
    • increases in volcanic activity and resulting aerosols could no longer cause surface cooling
    • El Nino/La Nina cycles could no longer cause variations in global surface temperatures
    • changes in global albedo resulting in increased or decreased global absorption of solar radiation could no longer cause variations in temperature
    • changes in orbital parameters affected received solar radiation could no longer have an effect on climate
    • ...and any other factors - either known or unknown - that used to affect global temperatures could no longer have any effect.

    That would make CO2 one heck of a dominating factor, and it is so unreasonable that I think that such a belief falls into the category of "Impossible Expectations" in the five characteristics of science denial:


    ...but that may not be what you intended to mean, billev, when you made the statement I quoted above. If not, please feel free to expain further just what you expect in the way of evidence - what would convince you?

  30. Argggh. On editing, after a failed attempt to post, I missed the links to biilev's original comment. It is here. The thread is on this post.

  31. When I say contiuous warming I am referring to those parts of the NOAA graphs of Global mean temperature from around 1910 until the early 1940's and from about 1974 until around 2002.  I made no reference to the fact that those temperatures are obviously subject to the effects of other factors.  There is currently a World wide debate over whether or not to move from the use of fossil fuels in order to reduce the production of carbon dioxide because it is causing global warming.  What measurements have been made to show how much of the amount of temperature rise since around 1910 can be directly attributed to the rise in carbon dioxide levels?    


    [TD] Click the Intermediate tab in this post.

  32. billev: "I made no reference to the fact that those temperatures are obviously subject to the effects of other factors."

    Yet such a conclusion is the logial consequence of your statement that you expect "that temperature rise should be continuous like the steady, and accelerating, rise of CO2 in the atmosphere". You can't evade the logical consequences of your position by saying "I didn't say that". If you agree that your original statement is in conflict with your actual position, then please say so.

    As for measurements showing how temperatures since 1910 can be attributed to various factors, please look at the graphs in comments 2 (author's response) and 23, and read the text that describes them. In fact, read the entire chain of comments.

  33. Billev, what is done is to measure all the of known forcings acting on the climate and recalculate onto a common basis (as if change in radiative input at the top of atmosphere). See the graph in comment 2 or 23. (In fact read the responses to Kimura).  What theory would predict, is that climate would follow the net forcing. ie sum up all the positive and negative forcings.  This is discussed in some detail on this post.

    These are the measurements behind the attribution. You have already agreed that energy is not magically created and that climate change must have some cause.

    The relevant figure is:

    This is for surface temperature record. It is more striking for Ocean Heat Content which so far you have avoided, despite it being a considerably less noisy record than surface temperature. (The noise is surface temperature is ocean/atmosphere heat exchange.)

    Note also that you can run models with only natural forcings, only anthoprogenic forcings, or both. The results are these (IPCC TAR).

    Note that anthropogenic works better than just natural, but both is closest.

    Now it is good to be skeptical and demanding a high level of certainity in drawing conclusions, but I notice that you seem to be only applying that to the question of whether CO2 causes this. You stated here
    that you " I would tend to think it is an alteration in the Earth's relationship with the Sun". Where was the evidence that gave you that suggestion and did you look for the proof? The orbital forcings are extremely slow, but have been negative (would cause cooling) for millenia.

    The anthropogenic hypothesis passes the test of conforming to all we know about the physics of climate. The predictions made by the science (if not the strawman versions erected by pseudo-skeptics) fit extremely well with actual observations. I do not believe you can make that claim for any other potential cause of climate change.

  34. billev

    You seem to be assuming that the clearest correlation between rising CO2 and some climate signal will be against the surface air temperature record.  Thermodynamically, this isn't reasonable, your apparent underlying premise is wrong.

    The logic is as follows:

    • CO2 is the largest single driver of climate in our current state, but it is not the only one.
    • The Net of all drivers will determine the total radiative imbalance for the planet.
    • A positive imbalance will produce an accumulation of heat in the various components of the system.
    • Because of it's much higher thermal mass the oceans will represent the largest single location where heat accumulates. If the net of all forcings is positive, this is where we would expect to see the clearest, least noisy signal and the best correlation.
    • Much smaller thermal masses such as the atmosphere represent a much noisier signal and are not expected to show as clear a response.

    Near monotonic increase in the heat content of the oceans is the strongest, clearest expected signal based on the thermodynamics. Unfortunately air temperatures are the dataset of most interest to us since that is where we live. But they aren't the primary evidence of the underlying process, ocean heat is.

    If you look at the graph in comment 2 above, although it doesn't show the most recent years, it gives a good indication of what was happening in the first half of the 20th century.

    • GH Gases hadn't yet marched away as a clear forcing.
    • After the eruption of Santa Maria in 1904, volcanic activity was low until the eruption of Mt Agung in 1964.
    • Although it isn't clear from the graph, solar activity was likely a little higher.
    • Land use impacts were still small.

    In the late 20th century:

    • There was higher volcanic activity.
    • GH gases, particulary but not only CO2 had a much larger impact.
    • Solar output has been declining slightly.
    • Land use changes took off.

    And very importantly, prior to 1957 we dont have any meaningful data on ocean heat content. So we can't usefully investigate the extent that atmospheric warming may have been driven by heat transfers out of the oceans. So we need to be careful to not draw more conclusions than can be justified from the more limited evidence from the early 20th century. There is some evidence tentatively suggesting that the early 20th century warming was particularly in the Arctic, possibly suggesting a change in ocean currents in the North Atlantic.

    The data for climate change is a jigsaw puzzle, with clearer pictures in more recent decades and less certainty earlier on. But when the first analyses of past ocean heat content changes appeared around the turn of the century they were rightly labelled 'the smoking gun'.

    Atmospheric temperatures are incredibly important to us since they reflect what is happening where we live. But thermodynamically the changes in the ocean are the biggest piece of evidence.

  35. To state that CO2 at one cubic foot per every 2500 cubic feet of atmosphere is the leading driver of climate seems illogical to me.  Since 1880 there is a strong indication of a definite pattern of warming and pauses in that warming that does not appear to be compatible with CO2 being the the principal cause of the warming.  The various alternating periods of pause and warming have occurred on what appears to be a consistant schedule.  This makes it difficult to believe a constantly increasing entity such as CO2 or random climate effecting incidents are influencing this pattern of temperature change.


    [RH] Note that, your lack of understanding the science does not mean that the science is illogical. 

    Please note that posting comments here at SkS is a privilege, not a right.  This privilege can be rescinded if the posting individual treats adherence to the Comments Policy as optional, rather than the mandatory condition of participating in this online forum.

    Please take the time to review the policy and ensure future comments are in full compliance with it.  Thanks for your understanding and compliance in this matter.

  36. You claim that small concentrations of CO2 affecting temperature is illogical, but try here to  check your grasp of what is logical.

    Now try this for logical.

    Statement A: "pauses in that warming that does not appear to be compatible with CO2 being the the principal cause of the warming."

    Statement B: "temperatures are obviously subject to the effects of other factors."

    See the problem? What is more, both myself and Glenn have demostrated to you that when you take into the "other effects", the temperatures are accounted for. Did you somehow fail to read our posts, or do you just have trouble comprehending things that conflict what you want to believe? I would note, that our demostrations were not simply "hand-wavy" points but quantitive based on physics and measurement.

    "The various alternating periods of pause and warming have occurred on what appears to be a consistant schedule."

    Not that I can see at all. How about you put up some evidence to back what you believe instead of just making wild assertions and ignoring responses? Did you base your conclusions on facts you have studied or what you would prefer to believe?

    Current climate theory (asserting that earth's climate is changed by the net forcings, natural and manmade) is able to account for present and past climate change, qualitatively and quantitively, using only known physics. By contrast you seem to believe that instead climate is changed by some unmeasurable, undetectable natural cause which is nonetheless accumulating heat in our oceans at rate of 4 hiroshima bombs/sec. Now that to me defines illogical.

    Ignoring responses that people make to you and simply repeating wild assertions without evidence is sloganeering and not permitted on this site.

  37. billev @35, the dry mass of the atmosphere is 5.352 x 10^18 kg.  In 1883, Krakatoa errupted, ejecting 2 x10^10kg, or 3.7 parts per 1000 million of sulfur into the atmosphere.  That became the dominant change of effect on climate for the subesequent few years, reducing global mean surface summer temperature by 1.2 C in the following year.  The effects of the erruption are described by wikipedia, saying:

    "Global climate
    In the year following the eruption, average Northern Hemisphere summer temperatures fell by as much as 1.2 °C (2.2 °F).[10] Weather patterns continued to be chaotic for years, and temperatures did not return to normal until 1888. The record rainfall that hit Southern California during the “water year” from July 1883 to June 1884 – Los Angeles received 38.18 inches (969.8 mm) and San Diego 25.97 inches (659.6 mm) – has been attributed to the Krakatoa eruption. There was no El Niño during that period as is normal when heavy rain occurs in Southern California, but many scientists doubt that there is a causal relationship.

    The eruption injected an unusually large amount of sulfur dioxide (SO2) gas high into the stratosphere, which was subsequently transported by high-level winds all over the planet. This led to a global increase in sulfuric acid (H2SO4) concentration in high-level cirrus clouds. The resulting increase in cloud reflectivity (or albedo) would reflect more incoming light from the sun than usual, and cool the entire planet until the suspended sulfur fell to the ground as acid precipitation.

    Global optical effects
    The eruption darkened the sky worldwide for years afterwards, and produced spectacular sunsets throughout the world for many months. British artist William Ashcroft made thousands of colour sketches of the red sunsets halfway around the world from Krakatoa in the years after the eruption. The ash caused "such vivid red sunsets that fire engines were called out in New York, Poughkeepsie, and New Haven to quench the apparent conflagration." This eruption also produced a Bishop's Ring around the sun by day, and a volcanic purple light at twilight.

    In 2004, an astronomer proposed the idea that the blood-red sky shown in Edvard Munch's famous 1893 painting The Scream is also an accurate depiction of the sky over Norway after the eruption.

    Weather watchers of the time tracked and mapped the effects on the sky. They labeled the phenomenon the "equatorial smoke stream". This was the first identification of what is known today as the jet stream.

    For several years following the eruption, it was reported that the moon appeared to be blue and sometimes green. This was because some of the ash clouds were filled with particles about 1 µm wide—the right size to strongly scatter red light, while allowing other colors to pass. White moonbeams shining through the clouds emerged blue, and sometimes green. People also saw lavender suns and, for the first time, recorded noctilucent clouds."

    By your reasoning that the amount of CO2 in the atmosphere is too small to have a significant effect, it follows that Krakatoa could have had not effect on the climate as well, and the reports above are pure nonsense.

    The Sun shines steadilly, producing from 1360 W/m^2 to 1361.6 W/m^2 at the Earth's mean orbital distance over the entire historical sunspot record.  That variation of 0.06% of insolation, or 600 parts per million, is considered to be the major driver changes in the Earth's climate by some people.  By your reasoning with regard to CO2, however, it can have no effect.  That is particularly the case given that the current increase in CO2 concentration relative to the preindustrial changes the Earth's energy balance (all else being equal) by 1.9 W/m^2 or (once albedo is accounted for) by 69.6% more than the difference between the Maunder Minimum and the grand solar maximum of the 1950s.

    In essence, if your argument was valid against CO2, there are no changes in the Sun's radiation or atmospheric factors that could make any difference to the Earth's climate.

    Of course, your argument against CO2 amounts to an argument from incredulity.  It is not an example of reasoning, but of irrationality masquerading as reason.  The Dilbert quote in the above link is apposite. 


  38. billev:

    Your first sentence falls into the myth "CO2 is just a trace gas". (Follow the link to see why that is wrong. Same link that scaddenp posted.)

    There seems to be quite a bit that you just "can't believe". It's not a strong argument. (It's not an argument at all, as Tom points out in his last paragraph.) If all you can do is keep saying you can't believe stuff or don't see proof, then you'll soon get moderated out for repetition.

    [And I'll bow out, for now, to avoid the policy against dog-piling.]

  39. I will try to address the several statements directed to me.  First, the Krakatoa example is not a good one.  There is no comparison between the effect of the current level of CO2 and the effect caused by the gas and ash disgorged by the eruption of Krakatoa.  The graph showing the relationship between various forcings and the temperature record causes me to wonder why these forcings would follow such a reasonably precise 30 year pattern.  I would not think a continually increasing presence of CO2 would follow such a timed pattern. If opposed forcings caused the pauses in warming then, again, why such a patterned occurence?  One earlier post informed me that the warming pause in the 1950's and 1960's was caused by the presence of aerosols  What then caused the, "on schedule"  beginning of another pause shortly after 2000?  As far as the argument that small amounts can be effective I say that that is not always the case.  A one inch thick sheet of steel can stop a small arms bullet but a 1/2500th of an inch thick  sheet of steel cannot.  If a person cannot detect a rather precise pattern of warming and pause in warming in the Global temperature record starting in 1880 I can only say that to me the pattern is obvious.  Whether it will continue in the ensuing years who can say.  But I do believe that more attention should be paid to that distinct possibility. It would seem to offer a better prediction of future temperatures than most of the computer models have done. 


    [RH] Note that your comment here has a complete lack of supporting evidence or citations of any research in support of your position. We expect a little bit more from commenters on SkS than most other websites. You're more than welcome to argue your position but you're currently skating along a thin line of sloganeering. If you wish to retain your commenting privileges you're going to have to up your game a few notches.

    Alternatively, if you're here to try to learn something new about these issues, please acknowledge that you don't understand the science and other commenters who are knowledgeable will be more than happy to supply you with information, along with the requisite citations to review. 

  40. billev @39:

    "First, the Krakatoa example is not a good one. There is no comparison between the effect of the current level of CO2 and the effect caused by the gas and ash disgorged by the eruption of Krakatoa."

    Argument by assertion is likewise an example of irrationality masquerading as rationality.  It is also an example of 'sloganeering', as defined and prohibited in the comments policy.

    As the argument stands, you have supported your argument from incredulity by an analogy (bullet and steel sheet) but merely assert that the analogy applies with respect to CO2 increases, but does not apply to the much smaller (as measured by parts per million by mass) injection of SO2 into the atmosphere by Krakatoa.

    Perhaps you should support your claim by some basic facts, such as:

    A)  The preindustrial CO2 level raised the Global Mean Surface Temperature (GMST) by approximately 33 C (12.8%) relative to what it would have been in the absence of CO2.

    B)  CO2 levels have risen by 43% since the the preindustrial.

    C)  Therefore it is obvious because very thin sheets of steel will not stop a bullet that the increase in CO2 could not have had any effect on GMST.

    I can then introduce you to the idea of a non-sequitur.

    More seriously, as this example argument demonstrates, you rigourously refuse to quanitify your argument because any such quantification (if not ridiculous based on known facts) will show your argument to be an absurdity.  Instead you rely on arguments from incredulity, from assertion, and from unjustified analogies.  Specifically to your analogy, you have not shown that the preindustrial CO2 concentration has no effect, so that it is analogous to a steel thickness which has no effect.

  41. billev: "What then caused the, "on schedule" beginning of another pause shortly after 2000?"

    What pause?  It's already been pointed out to you that most (90%+) of the accumulating energy is being stored in the oceans, and much less (3-5%). is being stored in the atmosphere.  Why would you base your arguments about warming on such a small sample of the climate system?  This is akin to reviewing a restaurant after having had a bite of appetizer and a drink of tap water.  Ocean warming shows no "pause."

    Further, you do realize that the greenhouse effect has been directly observed, yes?  Surface-based instruments have measured down-welling longwave radiation from the atmosphere for a while now.  So you can make baseless claims about the greenhouse effect not being real, but you're simply wasting time.

  42. Actually I am starting to think billev is just trolling. He has so absolutely refused to look at the OHC record despite it being a better measure of global warming that surface temperature. Now why would that be? Tom has pointed out his outrageous claim that Kraktoa comparison is invalid. (If 400ppm of CO2 is "too insignificant to affect climate", then how come 3.9ppm of something else can?). He keeps going on about thickness of steel as if this was somehow relevant. (We can calculate whether given thickness of steel could stop a bullet just as we can calculate effect of 3w/m2 of extra radiation). If he is just here to have amuse himself at our expense, then I suggest "Do Not Feed The Troll."

    The obvious alternative is that he has a cognitive bias against AGW from either ideology or group identity that prevents him comprehending any contrary fact, which also means we are wasting our time in trying to educate.

  43. Because  "the something else"(sulphur dioxide) combined with moisture to form long- lived high altitude clouds which screened the Earth from the Sun's rays and caused cooler temperatures.  My steel sheet comments were in answer to the comments that pointed out how various small quantities could be effective,  My point is that not all small quantities are effective.  The current attempts to steer public opinion about man-made warming usually refer to the temperature records published by NOAA and GISS.  My statement about the pause starting about 2002 is based on how I interpret those published records.  I might add that I am not alone in that interpretation.  I also am of the opinion that once the current EL Nino ends then the pause will reassert itself and continue until about 2032.  I base that opinion upon the pattern of previous temperature change since 1880.

  44. So you agree that a very small amount of something can make a big difference after all. Want to try understanding why small increases in CO2 combine with other things to have a big effect as well?

    " I also am of the opinion that once the current EL Nino ends then the pause will reassert itself and continue until about 2032. I base that opinion upon the pattern of previous temperature change since 1880."

    Wow, that is bold assertion from someone refusing to understand physics. Still believing in the imaginary undetectable natural forces. I could do with some extra towards retirement saving. How much are you willing to bet on that?

    "The current attempts to steer public opinion about man-made warming usually refer to the temperature records published by NOAA and GISS."

    Clearly you have not actually read the IPCC reports. The surface record is important because we live on that surface. However, it is also very noisy because a small amount of energy exchange between ocean and atmosphere make a big difference to surface temperature. These are also unpredictable, though short in duration, and fool people into seeing patterns that dont exist if you bother to use something other than eyeball to analyze. The Ocean Heat Content does not have this problem and so is a better diagnostic of heat build up. Show me your cycle in that record. Show me any indication that build of CO2 has not continued to heat ocean. Do tell me where this energy in the ocean is coming from if not from anthropogenic.

  45. billev @43:

    "I also am of the opinion that once the current EL Nino ends then the pause will reassert itself and continue until about 2032. I base that opinion upon the pattern of previous temperature change since 1880."

    Crucially for Billev, it is an untested opinion.  It is only be not testing his opinion against data that he is able to retain it.

    In fact, several people have already made proposals of a similar nature to Billev's claim that the pattern of temperature will repeat themselves.  Specifically, Don Easterbrook has argued for a near repetition of the pattern; Akasofu has argued more abstractly that the temperature pattern is a gradually rising trend modulated by a sine function and short term variations; and Loehle and Scafetta have argued for a repeating, rising temperature pattern accelerated since 1970 by global warming.  As the linked articles show, none of these projections of temperature based on a cyclical pattern have been successful.

    Billev's own theory is indistinct.  He clearly rejects any forcing effect from CO2, and so cannot accept Loehle and Scafetta's projection.  He thinks the "cooling pattern" that he expects to repeat from 2000 onwards was evidenced in the "early 1940s" which does not align with the repetition from 1945 used by Easterbrook.  It is possible that he accepts a view similar to Akasofu's, but he is not explicit enough to be sure.  Regardless, neither a repetition of the 5 year running mean from 1940 (to match the early 1940s projection) or the Akasofu cyclical function matches the post 2000 temperature function:

    Billev's theory is a bust - something he does not know because he never quantified it and checked it against the data.  That is, he used feels to develop his theory, not reasoning, and certainly not scientific method.

    As Billev seems to have dropped discussion of the role of CO2 as a climate forcing, his remaining thesis is not on topic in this thread.  I would highly recommend that if he wants to defend his busted theory, discussion be moved to the theory that he thinks most closely resembles his (from the three links above), or failing that, to the general discussion of different projections here.

  46. Has there ever been any testing to examine the relationship beween the temperatures measured by the official measuring sites and the surface temperature at those sites?  It would seem to me that if the two changed proportionately then that would indicate that the surface temperature was the driver of that sites's measured temperature.  If the relationship was not proportional than it would appear that something in the atmosphere influenced the site's measured temperature.  As far as there being a continuation of the pause that began around 2002 and should continue until about 2032, if the experience since 1880 continues, we will have to wait and see.  I am too old to bet.  i won't be around to collect.  If the temperature record does plainly show a level line of global mean air temperature for the period in question it apparently won't be "seen" by those who are dubious about my remarks.  And by the way, I don't have a theory about trhe future.  I merely state that the past record seems to indicate a pattern of rise and pause that, if it continues, will be repeated in the future. 

  47. Billev, it's easy to see patterns.  That, in fact, is the human brain's extraordinary strength.  Critical thinking is a systematic way of testing the strength of apparent patterns.  You're failing at critical thinking because you refuse--for no apparent reason--to accept that CO2 absorbs and emits radiation at various broadened bands within the thermal infrared range.  That action--the central component of the greenhouse effect--has been established in lab for over a century, established through applications that rely on the effect's existence, and established through direct field measurement.

    If atmospheric CO2 increases, the climate system will store more energy.  Whatever alternative theory you propose, it must include that actually-verified component.  If you refuse to include that component, then your theory is never going to describe the Earth climate system.  It's like trying to explain human history without referring to economy.

  48. Tom,

    I do not remember seeing Krakatoa used as an example against the "CO2 concentration is too low to make a difference" argument.  I thought it was an excellent argument since it is weather and the concentration of SO2 is so much lower than CO2.  Thanks for the new argument.

  49. billev @46 now claims to not have a theory despite previously asserting:

    "I also am of the opinion that once the current EL Nino ends then the pause will reassert itself and continue until about 2032. I base that opinion upon the pattern of previous temperature change since 1880."

    Of course, if he had an opinion about future temperatures trends, he had a theory about future temperature trends.  It may be a "dinky little theory", but it is a theory none-the-less, even if he want's to deny that when faced with its refutation.

    He now retreats back to a mere tautology, that:

    "I merely state that the past record seems to indicate a pattern of rise and pause that, if it continues, will be repeated in the future."

    Well of course if the pattern is in fact continued, it will continue into the future.  That is what continued means.  But the graph @45 has already shown the pattern has not continued.  And therefore as the antecedent of your tautology is false, so also is the consequent.

  50. I have just reviewed several charts of temperature history from a variety of sources including NOAA and NASA and they indicate a pause in warming starting about 2002.  None of the charts I reviewed appears to be similar to the chart @45.  What about my question @46?

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