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Climate Hustle

Newcomers, Start Here

Posted on 15 August 2010 by John Cook

Skeptical Science is based on the notion that science by its very nature is skeptical. Genuine skepticism means you don't take someone's word for it but investigate for yourself. You look at all the facts before coming to a conclusion. In the case of climate science, our understanding of climate  comes from considering the full body of evidence.

In contrast, climate skepticism looks at small pieces of the puzzle while neglecting the full picture. Climate skeptics vigorously attack any evidence for man-made global warming yet uncritically embrace any argument, op-ed, blog or study that refutes global warming. If you began with a position of climate skepticism then cherrypick the data that supports your view while fighting tooth and nail against any evidence that contradicts that position, I'm sorry but that's not genuine scientific skepticism.

So the approach of Skeptical Science is as follows. It looks at the many climate skeptic arguments, exposes how they focus on small pieces of the puzzle and then puts them in their proper context by presenting the full picture. The skeptic arguments are listed by popularity (eg - how often each argument appears in online articles). For the more organised mind, they're also sorted into taxonomic categories.

Good starting points for newbies

If you're new to the climate debate (or are of the mind that there's no evidence for man-made global warming), a good starting point is Warming Indicators which lays out the evidence that warming is happening and the follow-up article, 10 Human Fingerprints on Climate Change which lays out the evidence that humans are the cause. More detail is available in empirical evidence that humans are causing global warming. Contrary to what you may have heard, the case for man-made global warming doesn't hang on models or theory - it's built on direct measurements of many different parts of the climate, all pointing to a single, coherent answer.

Another good starting point is the SkS climate graphics page, with each graphic featuring links to informative SkS material. Good introductions to climate science can be found at Global Warming in a Nutshell and The History of Climate Science. You could lose yourself for hours in those pages!

Smart Phone Apps

For smart phone users, the rebuttals to all the skeptic arguments are also available on a number of mobile platforms. The first Skeptical Science app was an iPhone app, released in February 2010. This is updated regularly with the latest content from the website and very accessible in a beautifully designed interface by Shine Technologies. Shine Tech then went on to create a similar Android app which has some extra features missing from the iPhone version. A Nokia app was also created by Jean-François Barsoum (this was one of the 10 finalists in the Calling All Innovators competition).

As well as the list of rebuttals, Skeptical Science also has a blog where the latest research and developments are examined and discussed. Comments are welcome and the level of discussion is of a fairly high quality thanks to a fairly strict Comments Policy. You need to register a user account to post comments. One thing many regulars are not aware of is you can edit your user account details (to get to this page, click on your username in the left margin).

Keep up to date by email, RSS, Facebook or Twitter

To keep up to date on latest additions to the website, sign up to receive new blog posts by email. There's an RSS feed for blog posts and for the engaged commenter, a feed for new user comments. I recommend you follow the Skeptical Science Twitter page as I not only tweet latest blog posts but also any other interesting climate links I happen upon throughout the day. New blog posts are also added to our Facebook page.

About John Cook

Lastly, for those wondering about who runs Skeptical Science, the website is maintained by John Cook. I studied physics at the University of Queensland but currently, I'm not a professional scientist - I run this website as a layman. People sometimes wonder why I spend so much time on this site and which group backs me. No group funds me. I receive no funding other than the occasional Paypal donations. As the lack of funding limits how much time I can spend developing the site, donations are appreciated.

My motivations are two-fold: as a parent, I care about the world my daughter will grow up in and as a Christian, I feel a strong obligation to the poor and vulnerable who are hardest hit by climate change. Of course these are very personal reasons - I'm sure everyone comes at this from different angles. I go more deeply into my motivations in Why I care about climate change.

The SkS Team

However, there are many more who make invaluable contributions to Skeptical Science. There are a number of authors who write blog posts and are currently in the process of writing all the rebuttals in plain English. Translators from all over the world have translated the rebuttals into 15 different languages. There have been contributors to the one-line responses to skeptic arguments, proofreaders, technical support from boffins who understand computers a lot better than myself and commenters whose feedback have helped improve and hone the website's content. Skeptical Science has evolved from a small blog into a community of intelligent, engaged people with a commitment to science and our climate.

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Comments 101 to 150 out of 207:

  1. Hopefully someone can point me in the direction as to where on this sight I can get an answer, or create and respond to my question as I have been unable to find it addressed.

    As the elimination of the northern ice cap continues, which happened 120,000 years ago, the naturally resulting CO2 release that has been going on for 11,500, is decreasing, and will stop when the ice cap disappears. The resulting slowing of the thermohaline circulation will reduce the well up of massive amounts of CO2 from the ocean floor. The warming of the oceans will, however, increase the ability of ocean CO2 absorption. This reduction of CO2 emissions, coupled with increased CO2 absorption, will dwarf the 40 billion tons of man caused CO2 emissions.
    The ratio of natural emission to natural absorption as well as the rate of increase of absorption due to ocean warming and the rate of decrease in CO2 emissions due to reduction of ice to be melted, and a slowing of the thermohaline circulation and the resulting slowing of CO2 release needs to be considered. This has huge implications as to the temperature rise limitations and time frame to reach the turning point of what some might describe as the man caused extenuation of the Inter-glacial, glacial turning point.
    Because I am unable to find this addressed anywhere, I am having difficulty in formulating what you like to address: a simplistic sceptic question.
    Perhaps this is not a question that is skeptical of global warming but rather why these effects of global warming appear not to be address by those that would have us believe that they know the likely end result.
    I suppose no one will address this and this post will be deleted as it is "off topic" of being skeptical of global warming and is only skeptical of the results of global warming.
    But hopefully it has been effectively addressed and someone can show me where.
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    Moderator Response: You are repeating the claim that warming oceans will increase CO2 absorption, after you were corrected. If you're going to post questions on this site, you need to read the answers.
  2. "a simplistic sceptic question." should of course be a simplistic skeptic question.
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  3. stephenwv - I'm certain that I won't be the only person responding, but there seems to be little that is correct in your statements.

    - Melting ice doesn't release or absorb CO2. I have no idea why you would think that. It's relevant for ocean level and Earth albedo (water is darker than snow, less snow -> more warming).
    - Warmer water holds less CO2, not more: warming oceans will reduce the amounts absorbed (as a sink) by the ocean. Past glacial cycles show the oceans releasing CO2 as they warmed, which we're not seeing currently only because the CO2 atmospheric level is so much higher from our emissions than the temperature related ocean equilibrium solubility point. Our atmospheric CO2 is increasing at ~2ppm/year, while we put out emissions that would show as ~4ppm/year of rise. That means the oceans are absorbing CO2, not pumping it out!
    - Currently our 29GT/year (not 40GT total, by any means - that's less than three years!) is being about half absorbed by the oceans, acidifying them. Some of that is currently on it's way to the benthic ocean, which is by no means a source of CO2. It's a sink.

    So: Your questions do not appear to be addressed here because I've never seen them presented as arguments - they're simply not true. Melting ice doesn't release CO2, ocean circulation won't magically suck up extra CO2, thermohaline circulation is not pumping gobs of CO2 into the atmosphere.

    I suggest reading some of the links I've put into this post, this "Newcomers" page we're on, and from the Big Picture thread.
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  4. KR,

    Your post is the third time the "warming oceans absorb more CO2" falsehood has been explained to him.
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  5. Trueofvoice,

    I have to say, that's the first time I've ever heard anyone claim that melting ice releases CO2.

    Unless it was dry ice - and since the poles aren't warming from below -57°C, that's definitely not the issue...
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  6. KR,

    I've searched for the argument that melting ice liberates CO2 but can't find a single reference for it.

    Stephen, where did you get this idea from? Do you have a link?
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    Moderator Response: (Daniel Bailey) Closest I've heard is Goddard's post on CO2 snow in Antartica.
  7. The only reference I have found to CO2 ice in polar icecaps is from Mars, where the CO2 ice component of the polar caps is melting, revealing that the majority of the Martian icecaps are actually water ice.

    Hardly relevant to Earth, however, as surface temperatures here don't go low enough to freeze CO2 (Brrrr...).
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  8. Daniel Bailey - Interestingly enough (thanks to the wonders of Google) it turns out that WUWT posted a retraction on Goddard's statement. The partial pressure of CO2 is a primary factor in the triple-point (solid-liquid-gas) relationship for CO2. And the partial pressure of CO2 in the atmosphere is far far too low - sublimation occurs much faster than deposition, and dry ice will not form with Earth atmospheric mixes and temperatures.

    It's nice to see that sometimes, on occasion, WUWT does post a correction. Perhaps that group isn't a total loss...
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    Moderator Response: [DB] Thanks for the update (converted to link). Hadn't gone there since that original CO2post.
  9. Here's a reference that shows meltwater from ice takes up atmospheric CO2 -- and that an ice-free Arctic will lose that ability, making things even worse. Talk about feedbacks!

    “The total loss of summer sea ice from the Arctic, predicted to occur within the next few decades, may have dramatic effects on the ability of the Arctic Ocean to sequester CO2 from the atmosphere.

    “We could see further increases in CO2 accumulation in the atmosphere, if reductions in this “the sea-ice pump” are not compensated for elsewhere.”
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  10. NOTE: I wanted to have the quote and link at the bottom of this post read first, please do so. For some reason my entire comment would not preview if it led off. Sorry.

    I have always seen your credible blog posters discredit the referenced statement/author/website for false information rather than attacking the messenger (me). As this was not done, I was skeptical of the criticism. In retrospect, now it appears you only bring anti-AGW web site/studies/authors to task and not pro-AGW. As I was trusting of web sites basically controlled by the US Government, apparently, incorrectly believing that if they were not the most credible source of information, who was? In the past I have been skeptical of any sites that smacked of special interests and bias. Now you have taught me to be skeptical of the government sites, as well as how you apply your own bias of heavy criticism of anti-AGW anything, while you give a virtual free pass to pro-AGW anything. With that being said and understood, I do find your site to be the most helpful I have seen in sorting out the hysterical propaganda from the less hysterical.

    "WHAT IS GLOBAL WARMING DOING TO THE OCEANS? It's raising the oceans' temperatures ever so slowly, but also, it's making it easier for the ocean to absorb carbon dioxide (CO2)."
    Gov. AGU statement
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    Moderator Response: [DB] Fixed link (you were missing the closing double-parenthesis from the URL tag). Also, please refrain from using all-caps. Thanks!
  11. Regarding my belief that there was CO2 in ice, another NAS affiliated web site, states: “Atmospheric CO2 measured from bubbles in Dome Fuji ice shows the same pattern as the temperature time-series.” You tell me ice has no CO2 to release as it melts. Somehow I got the impression that they were measuring CO2 in ice. My bad. I thought NOAA was supposed to be a credible Government scientific organization, again, affiliated with the NAS. So I was not skeptical of their statement. I'm learning. Must be skeptical. Can't trust anyone. What the words say is not to be taken literally (or something).
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    Moderator Response: [DB] Fixed link (the system was not recognizing the italic double-quotes you were using).
  12. #110

    Context is paramount. At our current level of understanding, global warming is beimg caused by anthropogenic CO2 emissions. Increased atmospheric CO2 concentration makes it easier for the oceans to absorb CO2 despite the increased temperature that would otherwise cause the oceans to become a net source.


    The gas composition analysis of ice core samples is done through relative comparison of the minute gas pockets trapped in the ice crystal matrix. Melting ice is not a significant source of CO2.
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  13. @111

    I think you just have a basic misunderstanding. The gas bubbles in ice represent what was in the atmosphere at the time they were captured, which includes all gases. Releasing those gases together as the ice melts is not going to increase the parts per volume of those gases in the atmosphere.
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  14. #112 Prior to finding the reference of CO2 in ice core samples I had only heard there was no CO2 in ice. Recently I read that when ocean water freezes, there are pockets of unfrozen water that is trapped. This is supposed to allow concentrations of salt to form as the remaining water freezes. This suggests that the small amounts of CO2 present in the water would also be trapped. Do you have a link that would address any of this and the miniscule amounts involved that you state exist in the core samples. Am I correct that these ice core samples are not created directly from salty ocean water?
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  15. stephenev,

    The ice cores are from glaciers not frozen seawater.
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  16. #114

    It is correct to state that the Vostok ice core samples were not created directly from salty ocean water. The Vostok station is located in the center of the Eastern Antarctic ice sheet, hundreds of miles from the ocean.

    I apologize for not providing any supporting links as this is being tapped out from my phone, which does not support copy & paste.
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  17. stephenwv - The ice cores are taken from glacial and continental ice sheets, as floating ice doesn't tend to have been consistently present for tens or hundreds of thousands of years; a requirement when establishing a time-line.

    See the wiki Ice core page, also for related published work see the NOAA page on this.

    Ice cores trap tiny bubbles (I considered a Don Ho reference here...) of atmospheric gases as they form and compact (compact due to accumulating snow on top of them). Depending on the rate of snow accumulation at that spot the bubbles represent a few 10's to perhaps 100's of years sample (depending on the core site).

    Analysis of relative oxygen isotopes indicate local temperatures, amounts of CO2 show atmospheric concentrations, beryllium-10 concentrations are linked to cosmic ray intensity, which can be used as a solar activity proxy, dust is an indicator of volcanic activity, and so on.

    Note, however, that whatever gases melting ice releases (a very very small amount) is of the relative concentrations from when it formed. That means the CO2 concentration in such released melts is lower in CO2 (190-290ppm) than in the present atmosphere (395ppm).
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  18. The following journal article regarding sea-level acceleration from the Coastal Education & Research Foundation (CERF) was pointed out to me by a skeptical friend. Not being a scientist, I don't know how to respond. Any thoughts on these findings?
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  19. MMead, try this response to the paper:
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    Moderator Response: [muoncounter] Tamino's response was briefly noted on the latest sea level rise thread, which has excellent background information.
  20. MMead at 10:37 AM, somehow you've messed up the link, it directs straight back to the comments page.
    You can find out how to properly link by clicking on the tips for posting images or hyperlinks at the bottom of the comments panel.
    I have provided the link below and have tested it.

    However as it is a paper that finds decelerating trends in sea level rises, you should instead post it in a thread that addresses the controversy of whether any sea level rising trends are accelerating, or decelerating as your paper indicates.

    Sea-Level Acceleration Based on U.S. Tide Gauges and
    Extensions of Previous Global-Gauge Analyses
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  21. Stu and johnd, thank you for your replies. I thought I entered the link according to the tips provided, but being a technological dinosaur, I apparently did it incorrectly. My apologies and thanks for correcting it.
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  22. MMead at 07:18 AM, it's quite possible that you did enter it correctly, but sometimes gremlins do appear that cause links not to work as intended.
    At times the moderators will correct such broken links as is often noted on some posts, but obviously not always.

    I try to use the preview panel to make sure the link works, or even check it immediately as the post appears just to prove it out.

    If you are wanting more discussion about the study you presented, it may yield more results if you repost it again on a more appropriate thread as it appears that it has not found much interest to comment here. Out of sight, out of mind perhaps?
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  23. It is good to glean information from arguments of people with different stand on an issue. I just hope that there be a sort of compilation or summary of all threads as it will become a daunting task of reading through all 800+ comments with some arguments going back 360 degrees and coming up with our own conclusion.
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    Moderator Response: (DB) A brief executive summary of climate science can be found on the SkS home page under the Big Picture button/link.
  24. Hey there.

    I do not believe that CO2 drives climate and I have many good reasons such as....


    The IPCC underestimates Solar forcing by up to six times...

    Doctoring of Data to show alarmist results (straight from Forbes if you've got a problem with it you are more than welcome to attempt to sue them)


    Real world Data

    AGW is based on increasing downwelling radiation, while over the 14 years of this study, CO2 increased 5% but Downwelling radiation decreased...

    Predictions repeatedly fail

    The top Japanese experts thing AGW is no better than Astrology...

    James Hansen just put out a paper admitting that climate models greatly exaggerate man made global warming...

    And Solar scientists don't believe in AGW...In fact it seems mostly only Climate scientists do...

    So there you have it, I think we've been paying too much attention to the cries of an infant science while mature ones tell us to hold off...
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    [DB] Quite frankly, your comment betrays a lack of knowledge of the science of climate change, which is well-discussed here at Skeptical Science on many hundreds thousands of threads. 

    Please use the Search function to find individual threads for each of your points, such as CO2 Is Not The Only Driver Of Climate.  As constructed, your comment is essentially a Gish Gallop thus needing no refutation. 

    If anyone wants to respond to one of Cole's points, please do so on a more appropriate thread with a pointer here.  Thanks!

  25. Cole, you seem to believe "if I read it on the interwebs and want it to be true, then it must be true."
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  26. Hi. Love this web site. I commonly link others to it. Thanks for all the work you put into it.

    Here's my comment:
    I think it would be worth pointing out, if you agree, that so-called "skeptics" of global warming / climate change and the anthropogenic component of them, are not really skeptics at all, but denialists. Skepticism (about any one topic) is a temporary condition, open to change when the weight of evidence is clear. Whereas denialism is a permanent condition, immune to change no matter what evidence comes to light. So, what you are really doing is getting skeptical about global warming denialism.

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    [DB] Thanks for taking the time to post a comment.  We previously touched upon this situation in this post: Are you a genuine skeptic or a climate denier?

  27. Glad to be here John. And, good to see you on the Climate Show. Keep the faith... "Nature knows no indecencies; man invents them." - Mark Twain's Notebook
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  28. This is my first posting. I am not a scientist. I'm deeply committed to the seriousness of Climate Change and would like to add my weight but I am drowning in the science. I think it is the very complexity of the science in this debate that keeps it from being taken as seriously as it needs. I think we regular folks need an attention getter, 'an asteroid', figuratively speaking. Please indulge me a moment. As I have read the pros and cons from so many informed persons, it is apparent that one needs more education in climate science than I possess to follow the debate at ground level, so to speak. But like many persons, who I assume the science community would want to reach, I possess a logical mind. If higher-end estimates of Global Warming prove to be true, I think this would constitute the most significant challenge mankind has ever faced. How does the average person get past the science and search for the truth? Too many still feel helpless; that whatever climate change there is, is simply a natural fact of life on earth, which we will all have to live with, but can't alter. And many are counted among the millions who still believe that global warming is untrue or a 'hoax'. The debate rages even after the results are in and scientists have made their point. Its confusing. So I try to imagine a parallel scenario, easier for my limited scientific mind to grasp. A poor analogy perhaps, but let's say tomorrow, a gathering of the world's leading astrophysicists announced that after ten years of examining the data, there was a 90% probability of earth's collision with a one-mile-wide iron asteroid in a hundred years. The debate would be different. For one thing, it would be short, not decades long. We'd be checking the data, doing our homework as individuals and families, and establishing a global consensus. We'd be listening to out top scientists and mathematicians. We'd have less patience with unqualified opinions that confuse, and the audience these persons would draw would shrink dramatically. We would get on with what mankind might do to mitigate the problem before it shows up on our grandchildren's doorstep at 27,000 MHP.

    Some of the upper-end estimates of global warming during the next 100 years are barely less onerous to humanity than my poor asteroid example. So what's the problem? Logic might answer that question as well. On one side we have a dedicated group of Climate Scientists who are telling us what their research indicates. Collectively, they have limited financial resources, but they do have education, dedication, and years of hard won facts. Are they perfect? No. But are they right to a reasonable, logical certainly? Yes. On the other side of the fence, we have the largest man-made entity on this planet, the Fossil Fuel Industry. And in their corner, we also we have the Auto Industry, the Electric Utility Industry, and most Governments. If this were a prize fight, I know where my money would be. Logic tells us that money is what is controlling this debate. An unlimited supply of money to recruit, and finance, and confuse people like me who are just trying to sort out the truth and try leave my grandkids a reasonably civilized world. I, after all, helped to create the problem. So I look at the the facts (or non facts) of climate change logically. Some say the world is too big for man to have a significant effect on our climate. Logic tells us that mankind has developed the technical capability to do just that. Few if any, for example, argue that the climate would change if mankind engaged in all-out nuclear war. That's probably why we haven't done it yet. Logic points to many aspects of this issue which are measurable. We may argue the methods somewhat, but 2% is not 1% and words can't change that, no matter the money paid and the credentials touted. We can measure CO2 over time. We can measure temperature and sea level changes. We can input new data from the past by analyzing Ice-core samples and input new paleoclimatological data from past millinea. And we know carbon chemistry. Even I know if you burn fossil fuels, CO2 is released. If you burn a little, the earth stays in a state of relative balance. If you burn a lot, CO2 increases. We understand the physics of a greenhouse gas. CO2 and methane are biggies. The more greenhouse gases in the atmosphere, the hotter it gets. And logic helps us sort out 100 years of 'the hottest year on record', or 'the strongest storms', or 'biggest floods'. The earth is talking to us and its telling us the climate is changing, and it ain't linear. Maybe we are, after all, just like the frog in the 'slowly heating pot of hot water' experiment. Maybe, even if we're looking at a 6 degree ambient atmospheric temperature increase, it happens so slowly in any one persons experience, that its just too hard to focus and 'suffer now to save later'. 'They' say the frog just sits there and slowly boils to death. Is that us? I think we need an asteroid to get everyone's attention. What would that be?
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  29. 128, Charlie,

    You make a lot of fair points, with only one quibble (people will likely start to feel climate change in unpleasant ways withing 30 to 50 years, not 100, so if you are a man in his fifties, your children will likely suffer directly, and if you are in college yourself then you will suffer... not greatly, perhaps, depending on your luck, but it will begin to intrude on lives in nasty ways before 100 years pass).

    But you identify three problems.

    The first is that the science is too complex. True, but unfortunately it is what it is.

    This is not an issue in medicine, where you don't understand everything about how the human body works, but you trust the doctor. Or law, or finance, or anything else. You trust someone who does know. (See this article for more.)

    Which leads to the second problem, which is that unlike your personal health or your asteroid problem, there is a group that benefits financially from CO2, no matter how dire the effects on the globe and humanity, so they are actively working to confuse you. The science is only that complicated if you have to get into it knee deep, which is what you have to do because the denial industry tries to fabricate 10 arguments for every piddling detail within the science.

    But your third problem, the idea that people need a shock effect that they can see and relate to to actually take action... that is, sadly, a part of human nature, but one for which there is no solution. Climate change is slow. Natural climate change takes thousands to millions of years. Anthropogenic climate change is still going to take more than a human lifetime to begin to show the true peril it represents.

    There's no getting around that. The thing is, if you jump off of a really tall building, it's going to be a while before you feel the effects. Until then, it's a really fun ride. But that doesn't mean you do it.

    Human intelligence is founded on being able to understand and predict events. It's based on knowing that if you stick your hand in the pretty red flickering light (i.e. a fire) it is going to hurt.

    So that's really where we stand. People need to think. They either need to learn the science (properly, not by believing the first bit of comfortable denial tripe that they hear) or else to trust the experts that do know.

    The third course... failing to learn, but distrusting those who are qualified in favor of those who tell you what you want to hear (and what they want you to think) is an unfortunately common aspect of human nature, but in this case it is one that is going to define our future.

    The most you can do as an individual is to learn as much as you can, figure out whom you can really trust, and to try to convince as many other people as you can to do the same, and to recognize that it is important. It may not seem like it now, but eventually we're going to hit the pavement, and the only way to stop that is to have never jumped off the ledge in the first place.
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  30. Thank you Shaerica for the balanced point of view. I fear you are correct in the end. As individuals, we may only be able to inform the people whose respect and trust we enjoy and try to get them, in turn, to pass it on. I agree with your assessment---tomes of material to get mired in. I limit my exposure by studying the source first. That generally takes care of the great percentage of 'informed sources,'---a great time saver. I still think we need an 'asteroid'. First atlantic hurricane with of 200+ MPH when it hits a major city. I'm not hoping for it on compassionate grounds, but that ought to do the trick.
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  31. 130, Charles,

    Unfortunately, even a huge hurricane will be written off by deniers as just a fluke (and they'll find anecdotal evidence of a 1743 hurricane that was even worse, or argue that while the wind speed was high, the actual loss of life and total precipitation were dwarfed by some MWP hurricane).

    The "asteroid impact" you are worried about will probably need to be something like a radical and unexpected sea level rise, or the abrupt transition of a huge swath of the Amazon to savanna as a result of repeated, extreme droughts... or maybe ten years of continuous, worsening water shortages in Texas (which would be a lamentable poetic justice for some, seeing as the state has enjoyed immense profits from fossil fuels in its history).

    But those events are unlikely in the near term, and only an uncertain maybe within 30 or 50 years. The sad fact is that AGW is more like lead poisoning than cyanide.

    If you want a good, approachable start to the science, though, I suggest to anyone and everyone that they start with Spencer Weart's : The Discovery of Global Warming
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  32. Here we go again :-(

    More hacked emails released
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  33. Help me with this one. The greenhouse effect if roughly 33 degrees centigrade which is the result of greenhouse gasses in the atmosphere. The planet has warmed from an increase in greehouse gas concentrations from roughly 15,250ppm before human influence to about 15,385ppm today. (water vapor is in the neighborhood of 1.5%) That is an increase of 0.9%. So the planet should be roughly 0.3 degrees warmer as a result than it would be otherwise. Because there is a "human fingerprint" we have to assume that carbon dioxide traps more heat than an equal amount of water vapor. Has this ratio been determined scientifically or is it based on observed warming?
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    [DB] Thanks for taking the time to post a question/comment!

    "The planet has warmed from an increase in greehouse gas concentrations from roughly 15,250ppm before human influence to about 15,385ppm today."

    Umm, no.  The current atmospheric CO2 levelsfor October 2011 are 388.92 pp.  Pre-industrial concentrations were about 38% below that. Also, the planet has warmed due to a number of combining factors, just one of which is the rising CO2 levels.  It is fair to say, however, that the majority of the warming experienced globally over the past 40 years is largely due to GHG's, of which CO2 is the chief.

    "So the planet should be roughly 0.3 degrees warmer as a result than it would be otherwise."

    You assume an instaneous, or linear response.  There is a 30-40 year lag in effects, largely due to the thermal inertia of the oceans, but also due to the effects of aerosols, which act to delay the onset of the warming effects of rising levels of CO2.  And actually, the planet has warmed some 0.6 degrees since pre-industrial (with another 1.x something "in the pipeline").

    "Because there is a "human fingerprint" we have to assume that carbon dioxide traps more heat than an equal amount of water vapor."

    Umm, you need to remember that rising CO2 levels cause warming, a forcing, which then act to increase water vapor levels (warmer air holds more moisture) which then act to also raise temperature levels (a feedback).  Further feedbacks (melting permafrost and changing land/use patterns due to human factors and drought) can also release more CO2 yet, further amplifying the warming.  Think of CO2 as the temperature control knob of planetary temperatures.

    I also recommend watching this video on why CO2 is the biggest climate control knob in Earth's history and reading The Big Picture.

  34. imthedragn, where'd you get the 1.5% water vapor statistic? I think I've usually seen around 0.4%. In any case, all greenhouse gases are not created equal.

    You also say that 0.9% of 33 C is only 0.3 C... but what logic underlies the assumption of a Celsius scale for this 'analysis'? If we switch to Fahrenheit then 33 C becomes 59 F... or if we go over to Kelvin it is 306 K. 0.9% of 306 K is 2.75 K... which is also 2.75 C. :]

    In short, your underlying calculation (and most of the values) is clearly incorrect.
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  35. CBD.. The 1.5% is just a number I threw out to as a basis of scale. I nor anyone else knows the exact average atmospheric H20 content. I have seen numerous sources that indicate water vapor as between 1 and 2 percent and as high as 4%. I just grabbed 1.5% as a starting point. The actual numbers don't really matter as much as the point that co2 has a greater effect than an equal amount of water vapor. I have been struggling for year to find something difinitive. So far everytyhing seems to point to pure conjecture based on observed warming. Your comments nonetheless are appreciated. I agree that my values and calculations are incorrect, they weren't meant to draw any conclusions, only to make an oversimplified point.
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  36. [DB] Thank you for your response. I will definately follow those links. I understand that humidity precipitates out of the atmosphere while GHGs linger for decades. You mention that rising temperatures cause higher humidity which causes even more warming. Wouldn't any rise in humidity cause enough warming to raise humidity? if raising temperature raises humidity which further raises temperature, then humidity alone should cause the same effect. I am not trying to say that CO2 is not causing any wamring, I only question the warming causing humidity feedback loop. Lastly, if CO2 is more effective than an equal amount of water vapor at retaining heat, why then isn't Mars noticably warmer. Mars does have over 10 times as much CO2 in its atmosphere than Earth.
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    Moderator Response: For practical purposes, humidity cannot be raised above the level that the current temperature supports. Of course there are small and temporary deviations above that level, but they are so short-lived (about 10 days) that there is inadequate time for any significant warming. Remember also that that nominally single level really is an average across lower and higher levels spread spatially and temporally. In contrast, CO2 and other warming causes last long enough for significant warming to occur. See also the Argument "Positive feedback means runaway warming."

    Regarding Mars: Although there is relatively much more CO2 in Mars's atmosphere than in Earth's atmosphere, the absolute amount of CO2 is still far too small to, by itself, trap (delay) much infrared radiation. More importantly, there are almost no other greenhouse gases in the Martian atmosphere, so CO2 is left to do the entire job by itself. In particular, there is no H2O in the atmosphere to feed back the warming. See the online text "The Planets" by Seligman.

  37. 136, imthedragn,

    A rise in humidity would cause warming, but what would cause the rise in humidity other than warming? And as soon as something else (anything else) swung temperatures back down, humidity would drop.

    The key to this is that humidity is almost entirely dependent on temperatures. If temperatures rise, for whatever reason, humidity will increase, raising temperatures even further. If temperatures drop, again for whatever reason, humidity will drop, decreasing temperatures further.

    Of course, unlike CO2, H2O is not entirely "well mixed" in the atmosphere. There are moist and arid regions of the earth, and since it is heavily dependent on the temperature of the air, humidity changes with altitude. Changes are seasonal and latitudinal (the further from the equator, the cooler and therefore less humidity). Water is transported by advection far more than diffusion. This is why you can't get a good, hard number for the percent H2O in the atmosphere, because it is not evenly distributed and it is constantly changing.

    The basic facts are:

    1) Humidity is dependent on temperature
    2) Increasing temperatures increase the ability of the atmosphere to hold water
    3) The change in lapse rate will also increase the ability of the upper troposphere to hold water
    4) Increasing temperatures will increase evaporation, providing the water
    5) Increases in humidity further increase temperatures
    6) H2O acts entirely as a feedback, not a forcing, because the response to temperature is so relatively fast as compared to other factors (like melting ice-albedo changes, out-gassing of CO2 from warming oceans, and ecosystem changes that release CH4 and CO2)
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  38. GREAT comments gentlemen. Look again at Mars. The realtive amount of CO2 is higher (by several thousand percent), but the absolute amount of CO2 exceeds that of the earth in excess of 10 fold. The thinner atmosphere effects the ability to retain heat. It also effects the "well mixed" amounts of CO2 in the dry upper atmosphere the same way. where the air is half as thin, the greenhouse effect of CO2 at that altitude is less than half (no idea by how much, just believe it not to be a linear realtionship)
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  39. 138, imthedragon,

    The thinner atmosphere is crucial. People often get so caught up in the radiative aspects of CO2 (and other greenhouse gases) that they lose track of the collisional transfer of energy. In the Martian atmosphere there is little to be heated except for the CO2 itself, so radiation dominates, and energy transfer up and out is quick, even if it must "make some stops along the way."

    In the Earth's atmosphere a very, very important piece of the puzzle is that closer to the surface, where the air is denser, CO2 absorbs IR, but before (usually) it is able to re-emit that energy, a collision with O2 or N2 transfers that energy to those molecules, which do then not as easily or as readily emit energy in the infrared. The end result is that surface radiation heats the CO2, and the CO2 heats the surrounding atmosphere.

    As one gets higher and higher in altitude the atmosphere becomes less and less dense, and the balance shifts, so that eventually radiation becomes the key factor, and CO2 acts to cool rather than to warm (i.e. collisions between O2/N2 and CO2 transfer energy from the O2/N2 to the CO2, which is then emitted as IR and potentially lost to space).

    Admittedly, this interaction is not crucial to the greenhouse gas effect (see Venus, which has roughly the same proportion of CO2 in the atmosphere, but where the atmosphere is far more dense and the GHG effect still dominates). But it is important to what happens on Earth, and to understanding some of the differences between the Earth, Mars and Venus.
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  40. Sphaerica, that is by far the best response I have ever seen to that question I had of Mars. The fact that surface temperatures are both much cooler and much warmer than they would be otherwise and that the "global warming" simply refers to the shift in those average temperatures really puts things in perspective form me. The remaining item in my mind that I need to clear up is defining a "static" greenhouse effect. By that I mean if we raise the CO2 level by x amount and then keep it there perpetually, the global average temperature will eventually stabailize to what. In my mind, regardless of how much you try to categorize things as forcings or as feedbacks, CO2 and water vapor both absorb infrared from a nearly identical portion of the spectrum, I still conceptualize them as if they were acting as a single gas.
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  41. So it is really the atmosphere and not greenhouse gasses that provides the stability of the temperature. Instead of frigid cold overnight and scorching heat during the day, the temperature stays more moderate because of the atmosphere even if the atmosphere were devoid of greenhouse gasses. The additional heating of the greenhouse gasses by their absorbtion of the infrared radiated from the planet's surface allows that average temperature to be nudged a bit higher.
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    [DB] "even if the atmosphere were devoid of greenhouse gasses"

    Umm, no.  Please read Atmospheric CO2: Principal Control Knob
    Governing Earth’s Temperature

  42. #140 imthedragon - it's important to remember that, although there's overlap between CO2 and water vapour, one condenses and precipitates at Earthly temperatures and one does not. Additionally, in the upper atmosphere, it's the radiation from CO2 that dominates due to pressure effects (see for example this RealClimate article or this excellent series by ScienceOfDoom). So while it's tempting to think of CO2 and water vapour similarly, you cannot, as one is doomed to be a feedback to the other's forcing, and one is not so prevalent or effective in the thin upper atmosphere.
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  43. 140, imthedragon,
    CO2 and water vapor both absorb infrared from a nearly identical portion of the spectrum
    This is wrong because, just like the radiation/collision aspect of things, the system is far more complex than that. It's not nearly as simple as just saying they overlap, so the change can't matter.

    For example, the concentration of CO2 proportionally in the atmosphere is fairly constant regardless of altitude, while the concentration of H2O drops the higher you go, because temperatures drop as you get higher and the ability to hold moisture in the air is temperature dependent.

    Why does this matter?

    Because a big part of what is changing, and causes greater surface temperatures, is that the altitude from which the planet radiates away its energy is increasing. The earth must have a mean global temperature of 255˚K when seen from space. It must, because that's the amount of energy that it absorbs from the sun. That can't change.

    What can change is the distribution of energy beneath the point where it radiates the energy into space, and the altitude where the radiation occurs.

    Picture the atmosphere, for the sake of argument, as a series of layers. Every layer absorbs IR, gets warmer, and radiates IR up and down. Above the lowermost layer, every layer is receiving IR from above and below. As you go up the air is less and less dense, with proportionally less H2O and the same concentration of but less total CO2. So as you go up more and more IR succeeds in radiating upwards, working it's way out into space, rather than downward and warming the surface.

    When there is less CO2, the layers above have less chance of trapping the outgoing energy. The radiation to space effectively occurs at a lower altitude.

    With more CO2, the layers above trap more radiation. Things progress upward, and the ultimate radiation to space occurs from higher layers.

    Add H2O, which overlaps with the CO2 absorption range. But H2O is not evenly distributed. It is more present in the lower layers, and more rarefied in the upper layers. So if you add CO2, and radiate the energy into space from high enough up, the overlap of CO2 and H2O is irrelevant.

    CO2 dominates.
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  44. 141, imthedragon,
    So it is really the atmosphere and not greenhouse gasses that provides the stability of the temperature...
    No. You are very grossly understating the role of greenhouse gases.

    As you already pointed out H2O is a very strong greenhouse gas and, as both skywatcher and I have explained, it dominates near the surface.

    So where do temperatures vary the most on earth, in a desert or in a rainforest? The latter has nice, cool trees to shade you, and yet it is stiflingly, achingly hot during the day and gives you little respite at night, too. The desert has burning sands in the day, but temperatures plummet at night.

    The difference lies in water vapor, the powerful greenhouse gas, that is pervasive in a tropical rain forest and prevents it from losing heat, but almost totally absent in a desert and so allows the heat to escape the moment the sun goes down.
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  45. Sphaerica, with respect, I believe your explanation @143 is incorrect.

    Placing imthedragon's question into context, the Earth's atmosphere contains just 8% of the CO2 contained by Mars'atmosphere. Further, CO2 provides approximately 20-25% of the greenhouse effect on Earth, or about 7 degrees C of warming. If the Earth's CO2 was doubled 3.5 times it would equal Mars' CO2, so on a simplistic view, Mars' greenhouse effect should provide about be 11 degrees warming. That is approximately double the warming it actually provides.

    A major reason for the shorfall is the lack of pressure broadening. Increased pressure widens the absorption band at the expense of reduced probability of absorption in the central peak.

    (From Science of Doom)

    Because in the central peak the atmosphere of both Mars and Earth have an optical thickness greater than 1, the effect of reducing pressure is to increase the altitude of effective emission from CO2 to space. However, it also greatly reduces the bandwidth of that emission, thereby allowing far more heat to escape directly to space from the surface, thereby greatly reducing the greenhouse effect. Mars' surface pressure is 4 to 8.7 mb (depending on season), so the effect is far greater than that illustrated in the diagram above.

    There are two other significant effects reducing the greenhouse effect on Mars.

    The first is that the adiabatic lapse rate on Mars (4.5 degrees C per km) is less than half of that on Earth, and significantly less than the environmental lapse rate of approx 6.5 degrees C/km. By itself, this factor would reduce the strength of the greenhouse effect on Mars by about 30%.

    The second is simply the other gases in the atmosphere. Given a layer of CO2 sufficiently thick to absorb all IR light in its absorption band, if we add another gas that does not absorb IR sufficient to double the atmospheric pressure, the thickness of that layer of CO2 increases. In doing so, the effective altitude of radiation of that CO2 also increases. The strength of the greenhouse effect is most simply calculated by assuming that the temperature at the effective altitude of radiation to space equals the equilibrium temperature of the planet (ie, that temperature which will result in outgoing radiation matching incoming radiation), and then deriving the surface temperature by the lapse rate. Increasing the effective altitude of radiation by adding neutral gasses therefore increases the strength of the greenhouse effect. Consequently, the large concentrations of oxygen and nitrogen on Earth increase the strength of the greenhouse effect on Earth relative to Mars, in addition to the other effects.

    As a final note, while adding neutral gases does increase the strength of the greenhouse effect, they do not have a direct effect on surface temperature (other than by equalizing the distribution of temperatures). In the absence of a greenhouse gas, adding neutral gases would have no ability to raise surface temperatures above the equilibrium temperature as greenhouse gases do.
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    Moderator Response: I suggest adding an Argument: "Why is Mars so cold when it has so much more CO2?" Include not just these reasons, but also an explanation that (and why) the amount of energy from the Sun reaching Mars is so much smaller than that reaching Earth. And give it a link to the Mars is Warming argument.
  46. Tom, my understanding is that the CO2 more or less immediately transfers energy from outgoing IR to the rest of the atmosphere. Wouldn't that heating of N2 and the O2 raise the temperature of the atmosphere from bottom to top (more at the bottom) and thus explain the higher lapse rate? Another way to look at it is that the overall mass of the atmosphere dictates the heat capacity but additional CO2 raises it slightly. Thus I think that imthedragn's point about temperature stability (141) is valid.
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  47. Eric, on temperature stability, I'm not sure what your point is. Have you read the Lacis et al paper DB linked to inline at #141? The remaining atmosphere without GHGs can provide a stable temperature ... if you like your temperature to be stable at -21C! Given the lack of water vapour in that atmosphere, I suspect the diurnal range would be pretty brutal round the mean figures too, though cloud cover would tend to moderate it.
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  48. Thanks skywatcher, I read the paper, but it merely repeats Tom's explanation about pressure broadening (as shown in Tom's diagram above). Is the lapse rate responsible for the 33C GH effect? If so, are changes lapse rate caused by uneven pressure broadening of increased CO2 (with more broadening at the bottom)? Seems like a valid but only partial explanation. What about heat transferred from CO2 to O2 and N2? I do not believe that can be ignored for both stability and warmth.
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  49. I think I can answer one of my questions. Pressure broadening in wikipedia is "Impact pressure broadening: The collision of other particles with the emitting particle interrupts the emission process, and by shortening the characteristic time for the process, increases the uncertainty in the energy emitted (as occurs in natural broadening)[3]. The duration of the collision is much shorter than the lifetime of the emission process. This effect depends on both the density and the temperature of the gas."

    Apparently the heating of the rest of atmosphere by GHGs is one part of pressure broadening. Then the other effect of the rest of the atmosphere is stability from thermal inertia. Both imthedragn and I may have been conflating warming and stability.
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  50. Eric (skeptic) @146, yes, imthedragon's point @141 is correct, if easily misinterpreted.

    In the absence of an atmosphere and ocean to both retain heat due to their heat capacity, and to spread heat around due to the motion of winds and currents carrying heat from the tropics to the poles (and to a much lesser extent, from day side to night side, the Earth would suffer similar diurnal temperature variation to that encountered on the moon, ie, between -157 degrees C and 100 degrees C. Instead of that 257 degree C range, we have diurnal temperature ranges of between 5 and 30 degrees C (approximately), and that is almost entirely due to the capacity of the atmosphere and ocean to absorb and retain heat.

    What is more, that capacity also warms the Earth. Bodies with very uneven temperatures radiate heat far more efficiently than bodies with very even temperatures. For example, even though the effective temperature of the moon, ie, the temperature it would need to be to reradiate the energy absorbed from the sun to space if it was all one temperature, is around 380 degrees C, its blackbody temperature is actually 270 degrees C. The difference is due to the very uneven temperatures on the moon.

    However, this has nothing to do with the 33 degree C difference between Earth's effective temperature and its mean surface temperature. If the Earth was of uniform temperature with no greenhouse effect, its surface temperature would be 255 degrees K. As the Earth's temperature is not entirely even, it would actually be slightly lower than that, a fact often ignored for simplicity. But without the greenhouse effect, the surface temperature could not be raised above the effective temperature, let alone by the 33 plus degrees that it has been raised.

    So, yes, the atmosphere apart from the greenhouse effect makes the Earth's surface temperature stable. And yes, the greenhouse effect does nudge the temperature higher. But the 33 degree K (12%) nudge is more than just a bit, and indeed is absolutely crucial to the possibility of life on Earth.
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