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Comments 43951 to 44000:

  1. Empirical evidence that humans are causing global warming

    Videre - it would be better if you put your questions in the relevant thread. Very very briefly (and if you have more then PLEASE respond in the right place):

    - natural flows in and out are very large, but also more or less balanced. FF is changing that. If you messed significantly with natural flows, you would be trouble fast.

    - CO2 and methane respond to change in temperature regardless of cause of change. They magnify (over very long time scales) any other forcing that changes temperature. Water vapour does same but more or less instantly. However, the feedback is not a runaway (k<<1) so equilibrium is reached. (see here for detail if you dont understand).

  2. Empirical evidence that humans are causing global warming

    That’s great, thanks. I looked at the Global Carbon Cycle link. That’s really great. What I don’t understand is that all the other parts of the carbon cycle, like the vegetation and land and the oceans and rock weathering are more than10 times the size of the fossil fuel and land use source, and I guess if they only changed like 5 or 10% they could either decrease or increase the CO2 as much as the fossil fuel burning. So if its just the fossil fuel that makes all the difference, then do we need to assume that all those other much bigger effects are staying constant within a few percent?

     

    Thanks for the link to the CO2 lag link too, but now I am more confused. It says that the initial rise in temperature was caused by astronomical things and then the ocean temperatures rose and CO2 then rose because it is less soluble in oceans if the temperature is higher. I guess that makes sense. But then does that mean that all those million years ago the same thing was going on? And I guess if the CO2 got released after the temperature went up in those long ago times and then started heating things up, I guess I don’t understand what stopped it. The other thing I guess is if the temperatures started going up and caused the CO2 to go up, how do we know that is not what’s happening now. I mean the ocean temperatures look like they are going up. How do we know, I mean from the data, that the CO2 rise in the atmosphere isn’t being caused by the rise in ocean temperature. I guess the other thing is if CO2 lagged temperatures in the past and then the greenhouse effect kicked things up a notch, so it should just keep going up. But if I look at the upper graph on the link, it looks like the temperature went up and then down a lot of times in the past 400 thousand years. So what I don’t get is, if the greenhouse effect kicks in and heats things up, then more CO2 gets released from the oceans, then more greenhouse effect kicks in, it seems like it should just keep going up and up? Or is there something else going on that is causing the temperatures to go up and down in thos 400 thousand years?  And i guess if there was something else going and we dont know what it was, how do we know its not going on now?  

    Thanks for the info on plant and animal species. I guess I was most curious about the cause effect relation between CO2, temperature, and other climate factors.

  3. Charles Krauthammer's flat-earther global warming folly

    Chrisoz @9

    Thanks for that.  I didn't know the best place to post it, and I am happy for the mods to delete it.  I just wanted to bring it to John Cook's attention.

  4. Empirical evidence that humans are causing global warming

    Videre, regarding your question #1:  No one has claimed that 400 ppm or 1,000 ppm of CO2 are bad for life in general.  But all individual species have evolved to thrive in certain environments, including a certain range of CO2 levels.  When any aspect of their environment changes "slightly" and/or "slowly," individual animals and plants might be able to cope, and even if individuals cannot cope, their species might be able to evolve to cope.  But if some aspects of their environment change "too much" and/or "too fast," individual animals cannot cope well or at all, and species cannot evolve fast enough to avoid extinction.  Making the whole thing even more precarious are the interdependencies of plant and animal species.  If just one species' numbers fall, or if their characteristics or behavior change, a large number of other species can be affected even to the point of extinction.  The big problem for us and all other current life is that CO2 is rising so fast that many species cannot evolve or move or otherwise adapt fast enough to the temperature and other climate changes, or to the ocean chemistry changes.  For some examples, see the post It's Not Bad, and be sure to read all three tabbed panes (Basic, Intermediate, and Advanced).

    Regarding increased CO2 increasing plant growth and using less water:  Yes, there are some benefits at some levels of CO2 increase for some plants.  But it is not a uniform benefit across all levels of CO2 or plants.  And increased growth of crops often means the extra growth goes into of the parts of the plants that humans don't use, such as woody stalks of plants whose leaves and fruit we eat.  More importantly, increased CO2 does not come by itself; it causes climate changes such as increased temperature and changed precipitation patterns, and ocean acidification that detrimentally affects fish, coral, and even vast numbers of microscopic creatures on which other creatures in the food pyramid depend.

  5. Charles Krauthammer's flat-earther global warming folly

    Fair enough Mr Kraut-hammer.  You don't beleive in climate change so forget climate change.  Look at the damage you are doing to your country which has nothing to do with climate change.

    http://mtkass.blogspot.co.nz/2010/10/forget-climate-change.html

  6. Charles Krauthammer's flat-earther global warming folly

    chriskoz @8:

    Krauthammer is one of a dozen or so ultra-right-wing appologists that we can all name who can be depended on to faithfully ignore facts to spout thier wingnuttery. Such people are not worth the space at SkS.

  7. Empirical evidence that humans are causing global warming

    This is good information. One thing I am trying to understand. If I look at the current understanding of CO2 levels over millions of years, reconstructed by a variety of methods like ice cores, plant stomata, and geochemistry, all put together, it looks like the levels of CO2 went up and down a lot and were way higher in the past than they were now, like 1000 or 1500 ppm. A recent paper on it is at

    http://ajsonline.org/content/311/1/63.short

    but there are lots of other papers like that too. So what I am curious about is

    1) During a lot of those times millions of years ago, the earth was fairly lush and had a lot of flora and fauna, and I guess evolution was taking place. I think man is supposed to have evolved about then.  But if 400 ppm or 1000 ppm are bad for life, why was there so much life going on then? I mean even now there’s a lot of stuff being published about how trees and plants and other flora are using water better, growing faster and things like that, for example the USDA just said trees are using water a lot better at

    http://www.nrs.fs.fed.us/news/release/trees-water-atmospheric-co2

    2) The CO2 levels went up and down a lot it looks like over millions of years so. I guess that means that a lot of natural processes affect CO2 levels? Or is it just man that does it? I mean what was making the CO2 go up and down for all those past millions of years?

    Just curious.  Thanks for your reply.

     

    Moderator Response:

    [TD] Excellent questions.  For answers to your question 2, see the post How do human CO2 emissions compare to natural CO2 emissions? (after you read the Basic tab, click and read the Intermediate tab) and the post Understanding the long-term carbon-cycle: weathering of rocks - a vitally important carbon-sink.

    For one specific example, see CO2 lags temperature - what does it mean?

  8. Empirical evidence that humans are causing global warming

    @Terranova #48:

    My satement about the rapidity of climate change being generated by mankind's activities is based upon a body of science very nicely articulated by Gavin Schmidt and Joshua Wolfe in their book, Climate Change: Picturing the Science, W.W. Norton Company Ltd, 2009.

    Here's what they say: 

    “Over eight glacial cycles in 650,000 years, global temperature and the amount of CO2 in the atmosphere have gone hand in hand. When temperatures are high, so are CO2 amounts and vice versa. This obvious connection is part of a coupled system in which changes in climate affect CO2 levels, and CO2 levels also change climate. The pacing of these cycles is set by variations in the Earth’s orbit, but their magnitude is strongly affected by greenhouse gas changes and the waxing and waning of the ice sheets.

    “Despite these large natural CO2 variations, atmospheric CO2 variations remained relatively stable over the 12,000 years from the end of the last ice age to the dawn of the industrial era, varying between 260 and 280 ppm. Methane, too, was stable during this period varying from 0.6 to 0.7 ppm. These trace-gas concentrations are well known from analyzing air bubbles trapped in ancient snowfall. This relative stability came to an abrupt end with the onset of the industrial era. At that point, we started transferring to the atmosphere carbon that had been stored in underground reservoirs for millions of years. These modern increases have occurred in a geologic blink of the eye, dwarfing the rate of increase coming out of the last ice age. Plotted on the same graph as the ice age change, the industrial era increases look like vertical lines.”

  9. The Consensus Project self-rating data now available

    Yeah Tom.I realised after posting the comment that i was going for the earliest point where there was a clash, rather than the most recent.

    I have added some more graphs to the TCP datavisualisation that show the accumulation over the years since 1991. It's currently being tested.

  10. Climate Change Denial now available as Kindle ebook

    Thanks chriskoz. Great idea.

  11. Charles Krauthammer's flat-earther global warming folly

    mandas@7,

    A news like yours belongs to SkS Weekly Digest or SkS Weekly News Roundup threads. Please post it there (and mods should delete it from here together with my comment herein) thanks.

  12. Charles Krauthammer's flat-earther global warming folly

    It'e worth mention the little fact that before 2012 election, Krauthammer predicted that the election would be “very close” with Mitt Romney winning the popular vote by “about half a point & Electoral College probably a very narrow margin".

    We know know, by  comparing to e.g. Nate Silver, that Krauthammer "prediction" had nothing to do with scientific polling & binomial distribution analysis but rather with unrealistic wishful thinking.

    Krauthammersince addmitted his prediction was incorrect but is still claiming that " that "Obama won but has no mandate." (source). So, in his illusionary world of "no presitential mandate", the only appropriate thing is to negate and deny what Obama says. I rest my point. It'w worthless to spend any more time listening to that man's comments.

  13. Rob Honeycutt at 16:33 PM on 11 July 2013
    Empirical evidence that humans are causing global warming

    Terranova @48...  "You cannot dismiss the contribution of water vapor."

    Definitely not dismissing it in the least.  I'm just saying that for the purposes of understanding what human factors of impacting changes in global temperature, the fact that WV is not on the spectral graph has no bearing on the point being discussed.

  14. Rob Honeycutt at 16:27 PM on 11 July 2013
    Empirical evidence that humans are causing global warming

    William...   "Where I live, H2O is a very long lived gas."

    Your comments demonstrate a fundamental lack of understanding of the physics being discussed.  WV is not a long lived gas, and as has be stated by others here, is also a condensing gas.  CO2, CH4, etc. are all long lived non-condensing gases in our atmosphere.

    Think about it this way.  What is the WV content of the atmosphere where you are when the temperature goes below zero C?

  15. Charles Krauthammer's flat-earther global warming folly

    John

    I know this is off topic, so I apologise for that.  But I had to provide this link to this thread at WUWT.  The conspiracy theorists are out in force today: http://wattsupwiththat.com/2013/07/10/macquarie-university-responds-to-murry-salby-termination-issue/#comment-1361244

  16. Philippe Chantreau at 13:08 PM on 11 July 2013
    Empirical evidence that humans are causing global warming

    Jason says " If humanity was busily attempting to artifically cause global warming by increasing atmospheric H2O levels, it would fail,"

    True but it's ironic that we kinda are attempting to do just that. Burning hydrocarbons can be summarized by the simplified relation: CH + O2 ---> CO2 + H2O.

    So we do release large amounts of water vapor in the atmosphere through the combining of atmospheric oxygen with fossil hydrogen. As I recall, the decrease in atmospheric oxygen has even been observed.

    So, William, even if your argument had any validity in physics (which it doesn't), it would constitute even more of a reason to decrease fossil hydrocarbon consumption.

  17. Empirical evidence that humans are causing global warming

    John @ 20: "Problem is that when those events occurred in the past, they gnerally occurred over a geological time scale."

    Terranova @ 48: "JH at 20: prove that statment. No models, but proof."

    Here you go, Terranova: http://tinyurl.com/l5wz6zc

    Ask a broad question, get a broad answer.  Did you want John to do your thinking as well?  Btw, science is not going to provide you with proof for a positive hypothesis.  Perhaps you meant "evidence."  If you want absolute certainty, go find a priest.

  18. Empirical evidence that humans are causing global warming

    William Haas, you seem to think that where you live is isolated from the rest of the climate system.  Are you sure you want to claim that dropping CO2 completely from the atmosphere would have no appreciable effect on your local water vapor concentration?  H2O is a powerful greenhouse gas, but it's also a fast feedback--not a forcing.  It responds very quickly to other forcings.  Its residence time makes it unable to produce any climate-scale trend in global energy storage (not even close).  It follows GHG forcing (rising rapidly).  It follows solar forcing (flat or falling for fifty years).  Harp on WV all you want, but it doesn't do the driving.

  19. Empirical evidence that humans are causing global warming

    William,

    One other point:

    H2O does not need any other greenhouse gas to exist in the atmosphere in order to provide its greenhouse gas effect.

    That's actually not true. With no CO2, the earth would freeze into a snowball and at low enough temperatures there will be no H2O in the atmosphere. The reason the earth escaped snowball earth situations in the past was because CO2 and methane released from vocanoes was not being taken up by rock weathering (due to the rock being covered in ice) allowing the concentrations to reach high enough levels that the greenhouse effect could melt the ice. The transitions between snowball earth and hothouse earth can't be explained without those other greenhouse gasses.

    So while H2O provides over half of the total greenhouse effect currently, it only does so thanks to the other greenhouse gasses. Again with the turbo analogy: no matter how powerful a turbo is, it has exactly zero effect when the car is switched off. Drive at 200 km/h and it could well be causing the engine to produce more than twice as much power as an equivalent engine without a turbo, but it's still dependent on the accelerator to do its job.

  20. Empirical evidence that humans are causing global warming

    William,

    The fact that H2O levels are high where you live is really missing the point. How long would an artifically induced change in those levels last?

    The answer is "a few weeks". If humanity was busily attempting to artifically cause global warming by increasing atmospheric H2O levels, it would fail, because any extra beyond what the atmosphere can carry will simply precipitate out. To increase H2O levels long term requires increasing the temperature, which is exactly how H2O acts as a feedback to warming by CO2.

    Contast this with CO2. It will take thousands of years for an increase in CO2 levels to revent naturally. During that entire time, the greenhouse effect is enhanced.

    As I mentioned before, H2O is the turbo, CO2 is the accelerator. Travelling at 200 km/h the turbo is probably responsible for quite a lot of the engine's power output, but that doesn't change the fact that the turbo is still a slave to the accelerator and it's the accelerator that's responsible. Nobody's ignoring H2O, we're just focussing on what actually matters when it comes to driving climate change.

  21. William Haas at 12:30 PM on 11 July 2013
    Empirical evidence that humans are causing global warming

    Honeycutt #47, Thank you for reading my post and commenting.  Where I live, H2O is a very long lived gas.  It is always there in very abundant quantity.  An individual molecule may leave the atmosphere but it is always replaced by another one,  H2O is the primary greenhouse gas and has a whole slew of LWIR absorption bands  H2O does not need any other greenhouse gas to exist in the atmosphere in order to provide its greenhouse gas effect.  H2O is the weather maker.  Ignoring it leaves a big whole in the argument.  "Dwarfs all other greenhouse gasses" cannot be inferred from the chart because the greenhouse gas that is responsible for most of the greenhouse effect was filtered out of the chart.

    Moderator Response:

    [GPW]: William, there are a few other points I'd like to make about water vapour (UK spelling). CO2 is now a precursor of warming, WV is a function of it. CO2 is well-mixed globally, WV is not. The residence time of CO2 is centuries or even millennia; the residence time of WV is days or weeks.

    We humans are not directly adding WV to the atmosphere (although it increases through chemical reaction and increased evaporation). We are adding CO2, methane etc. And finally, the reason WV was left out was explained by DSL earlier (thanks DSL), and in the paper from which the graph was obtained (post #10). I'll repeat the extract of the paper once more:

    From the paper: "The contribution of water vapour to the increase in greenhouse radiation has not been included since it is a part of the natural climate feedback. There is some argument to suggest that tropospheric water vapour has already increased by several percent; hence, the corresponding flux contribution may need to be included, but this effect is beyond the scope of current models."  

  22. Empirical evidence that humans are causing global warming

    Terranova @48, from forcings alone, we expect 3.7  Wm-2K-1.  That is, for each one degree C increase in temperature, we expect a 3.7 W/m^2 increase in outgoing radiation.    The observed ratio is 0.75 Wm-2K-1, the difference being the net effect of all fast feedbacks, including the water vapour feedback, so my calculation already includes water vapour.  It does not include slow feedbacks such as glacial melt so the final equilibrium response will be greater than that indicated by the calculation, although it will take centuries and possibly millenium to reach that equilibrium response.   

  23. Empirical evidence that humans are causing global warming

    Terranova,

    You cannot dismiss the contribution of water vapor.

    I wouldn't dream of it, water vapour is a significant feedback that approximately doubles the warming effect that increased CO2 would have on its own.

    But pointing it out in this context is like a driver complaining to the cop who just pulled him over for speeding that it's the turbo's fault that he was going so fast and not the position of his foot on the accelerator.

  24. Empirical evidence that humans are causing global warming

    Rob at 47

    TC at 46

    William at 45 made a point that is valid, and not moot.  You cannot dismiss the contribution of water vapor.  

    Mind you, I do not disagree that human actions have contributed to increased CO2 in the atmosphere, and the increased CO2 has led to some increase in temperature.

    And, JH at 20: prove that statment.  No models, but proof.

  25. Rob Honeycutt at 10:23 AM on 11 July 2013
    Empirical evidence that humans are causing global warming

    William @45...   Being that WV (which you're referring to) is not a long lived gas, it responds to the forcing from these other gases.  So, your point is moot.  Including WV doesn't change the accuracy of the statement.

  26. Empirical evidence that humans are causing global warming

    eklectikus @33, from 1900, total forcings have increased by approximately 1.56 W/m^2.  The current TOA energy imbalance is approximately 0.63 W/m^2 meaning there has been an increase in outgoing radiation of 1.2 W/m^2 due to increased temperatures of about 0.7 C over the twentieth century.  Therefore, each degree C of increased temperature results in about  1.32.  That means it would take a  2.8 C increase in temperature to compensate for a doubling of CO2.  It would also take a 1.35 degree increase to compensate for the increase in CO2 forcing since 1970.

    It is not that there is no empirical evidence.  It is that some people are eclectic about the evidence they will look at.

  27. Charles Krauthammer's flat-earther global warming folly

    I detest the moral bankruptcy of the argument that China is emitting more than the US, so the US need to nothing.  In fact, the Chinese individually (ie, per head of population) are emitting much less than US citizens individually.  Therefore it is incumbent on US citizens individually to reduce their emissions more than Chinese citizens individually; and on the governments of the respective nations, as agents of the people, to assist them in doing so.  Ignoring the per capita emissions tacitly endorses the claim that US citizens are entitled to a greater share of world resources (in this case energy resources) than Chinese citizens as a matter of policy.  Hence the moral bankruptcy of the argument.

    Not only is the argument morally bankrupt, it is also entirely hypocritical.  No supporter of the argument would endorse a global agreement on CO2 emissions which entitled Tuvalu or Monaco to the same national emissions as the US.  Doing so would limit the US to 0.5% of global emissions, compared to their current 18.5%.  They would undoubtedly reject such an arrangement as unjust based on differences in population; thereby rejecting the uniform application of the principle they want to apply to China to excuse their excess emissions.

    Somebody who trots out that argument deserves nothing but contempt. 

  28. The Consensus Project self-rating data now available

    Paul D @10, based on the interactive history, in the decade from 1961 to 1970, 20% of papers with a position where skeptical.  While still a majority opinion, that suggests acceptance of AGW was hardly a consensus at that stage.  Further, despite the evident overwhelming majority of papers endorsing the consensus from 1990, evidence from other sources suggest the consensus among scientists did not form until after 1995 and possibly not till after the Third Assessment report.  It is very evident, however, that once the number of studies per decade started increasing, the consensus formed very rapidly.

  29. Charles Krauthammer's flat-earther global warming folly

    men. Oops.

  30. Charles Krauthammer's flat-earther global warming folly

    The media outlets that carry such columns are in effect aiding and abetting the deniers. Krauthammer and George Will are two similar peas in the same pod when it comes to global warming denial. I take comfort that they are both old me.

  31. The Consensus Project self-rating data now available

    dana @9, the claim that "skeptics" are "more likely to pretend to endorse it in the abstract while claiming they rejected it in the full paper" is not supported by Poptech' sample.  One of Poptech's sample (Scaffeta) outrageously misrepresents the nature of the scientific consensus so that he can falsely claim an error in the abstract rating.  Shaviv's abstract, however, concludes:

    " Subject to the above caveats and those described in the text, the CRF/climate link therefore implies that the increased solar luminosity and reduced CRF over the previous century should have contributed a warming of 0.47 ± 0.19°K, while the rest should be mainly attributed to anthropogenic causes. Without any effect of cosmic rays, the increase in solar luminosity would correspond to an increased temperature of 0.16 ± 0.04°K."

    The increase over the 20th century was 0.7 K, so the paper attributes greater than 50% of warming to natural causes under an assumption the authors are willing to entertain. That indicates the paper should be rated (IMO) as at most a 5 (implicitly rejects), and certainly not, as it was actually rated, at 2 (Explicitly endorses).

    In like manner, Idsos' abstract describes the impact of enhanced growth on the seasonal cycle in CO2 and should probably (and at most) have been rated neutral, but was actually rated 3 (implicitly endorses).

    These two examples represent genuine mistakes.  Of course, Poptech has only found two genuine errors from among a very large number of abstracts rated as endorsing the consensus.  As always, he avoids mentioning the denominator.

  32. William Haas at 07:13 AM on 11 July 2013
    Empirical evidence that humans are causing global warming

    The statement: " But the spike for CO2 on the left dwarfs all the other greenhouse gases, and tells us something very important: most of the energy being trapped in the atmosphere corresponds exactly to the wavelength of energy captured by CO2." is wrong because the primary greenhouse gas in our atmosphere was not included.

  33. The Consensus Project self-rating data now available

    Nichol@5

    "How far would you need to go back to the time when there was still a reasonable controversy over climate change among climate scientists?"

    Try the An Interactive History of Climate Science gizmo.

    I suggest about 1900 or 1901 and the Angstrom/Arrhenius disagreement.

     

     

  34. James Madison at 04:47 AM on 11 July 2013
    Charles Krauthammer's flat-earther global warming folly

    ahh, I see, beer is not just for breakfast anymore, eh?

    If this is what one understands after reading the Krauthammer piece, then, well, one will never understand why climate change and its solutions are not taken seriously by the majority.

  35. Empirical evidence that humans are causing global warming

    #43 Amen.

  36. Dikran Marsupial at 04:22 AM on 11 July 2013
    Empirical evidence that humans are causing global warming

    Eclectikus, there are "skeptics" who claim that there is no such thing as the greenhouse effect, for example "Atmospheric "greenhouse forcing" does not warm the planet, never has and never will. In fact, the very idea that there is a greenhouse effect in our atmosphere is absurd.".  So while skeptics are generally letting go of climate myths such as "there is no empirical evidence" one by one, there is still a need to deal with these myths for the sake of those who have heard them from the misguided and want to hear the other side of the story.

    Please do not further disrupt the discussion of the science by trying to hold an off-topic meta discussion about what the site should be for.  SkS has been around for a while, and a fair bit of thought has gone into who the intended audience actually is, and which arguments ought to be addressed.

     

  37. Empirical evidence that humans are causing global warming

    Thanks heb0 #40. I'm an old reader of this blog, and just wanted to point out what I pointed out. In this case it's more like to tell my mechanic that the spark plug that he put to my car was secondhand. Question of nuances.

  38. Empirical evidence that humans are causing global warming

    DSL #37
    I understand that there is people with no background in Science, and that they form their opinion on the debate based on their political bias, but I did not know that this site was dedicated to those people, in fact, I'm pretty sure that that kind of people do not read these entries, and in the rare event that they stumble upon them, they will understand nothing. So if it comes to send a message, I think is better that the message be correct, and in someway to imply that skeptics discusses the anthropogenic CO2 causes some warming is fallacious. The dispute comes in how much warming, not in ellemental physics.

    Of course there has been a lot of improvement over the last years, in Climatology, and in all... but still we are in the first stadiums in terms of empiric verification, probably (surely) is not a scientists fault, is by the very nature of this Science. So a minimum of caution on predictions should be compulsory.

    If there were evidence of catastrophic character of the case, there would be no discussion, no one can be interested in destroying a planet or its inhabitants / customers. And use weather events of the present and the recent past does not seem very tight to the scientific method.

    Thanks for the link, I leave it as homework for tonight.

  39. Empirical evidence that humans are causing global warming

    @Eclectikus - The style of presentation of this website is to address specific myths about global warming. You're bringing up questions that this article doesn't claim to address and then comaplining whenever they aren't answered in it. A bit like throwing a fit at your local mechanic's shop because they don't stock croquet sets.

    If you're interested, there are other articles on this site that address the questions you're asking:

  40. Empirical evidence that humans are causing global warming

    In addition to the ASRB network [MeteoSwiss] reference @38 it may be useful to mention a very short and recently published overview [free access!] on the current status of measurements of radiation profiles by Philipona:

    Philipona, R., A. Kräuchi, and E. Brocard (2012)
    Solar and thermal radiation profiles and radiative forcing measured through the atmosphere
    Geophys. Res. Lett., 39, L13806, doi:10.1029/2012GL052087

  41. Empirical evidence that humans are causing global warming

    bouke @26: I always thought it was too difficult to measure this accurately enough. Could you provide a reference to this?

    The "classic" reference would be:

    Philipona, R., B. Dürr, C. Marty, A. Ohmura, and M. Wild (2004)
    Radiative forcing - measured at Earth's surface - corroborate the increasing greenhouse effect
    Geophys. Res. Lett., 31, L03202, doi:10.1029/2003GL018765.

  42. Empirical evidence that humans are causing global warming

    Eclectikus, "we" know it, but I talk with people every day who confidently claim that human CO2 does not contribute to global warming, and in fact that it's all a hoax.  This website is aimed partially at those people and partially at the people who are lying to to the claimers.

    I disagree on the no progress in thrity years claim.  Articulating the strength of the various forcings has come a very long way in thirty years.  You're going to have a hard time arguing that the last thirty years' worth of sensitivity, feedback, and modeling work has all been redundant and pointless.

    "catastrophic" as you define it is no definition.  All you're saying is "well, catastrophic as other people use and define it."  What does "catastrophic global warming" mean to you?

    Sure, CO2 concentrations are important for life at both ends of the ppm range.  Yet pushing the extremes of that range is not what the current problem is all about.  Within the context of rapid climate change via anthropogenic global warming, discussing the extreme ends of the range is irrelevant--basically a red herring made of straw.  Discussing the effect of the likely range of change on plant life is relevant.  

  43. Charles Krauthammer's flat-earther global warming folly

    Krauthammer is worried about the cost of transitioning to renewables because of "the problematic nature of contradictory data."  Is that like the data presented by weapons inspectors before the U.S. invasion to find Iraqi WMD?  The data that there WERE no WMD?  April22nd is now celebrated as 'Krauthammer Day', when he opined: "Hans Blix had five months to find weapons. He found nothing. We’ve had five weeks. Come back to me in five months. If we haven’t found any, we will have a credibility problem." uhh... ok...

    http://crookedtimber.org/2010/04/22/have-a-blessed-charles-krauthammer-day/

    And what did Krauthammer learn after spending $3 trillion in Iraq to obtain zero WMD? In 2004, he opined "we should have invaded Iran"!!  It should be obvious that 'the problematic nature of contradictory data' has never bothered Krauthammer before, and does not now.

    Krauthammer: "I’m not against a global pact to reduce CO2. Indeed, I favor it."  I like these 'standard disclaimer' lines at the end his piece.  As in: "The science on global warming isn't sufficient to do anything about CO2  ...  except a GLOBAL PACT REDUCING IT!!"  (by force of American military might, perchance?  What's not to love, for a neocon like Krauthammer?). 

  44. The Consensus Project self-rating data now available

    Not only is Poptech's sample of 7 much smaller than our author self-rating sample of 1,200 (and over 2,100 papers), but his sample is biased toward "skeptics" who are more likely to reject the consensus, and also apparently more likely to pretend to endorse it in the abstract while claiming they rejected it in the full paper.  Not exactly a compelling argument against our paper and conclusions.

  45. Empirical evidence that humans are causing global warming

    DSL #35
    But that is not the point of this entry. To say that there is "empirical evidence that humans are causing global warming", is meaningless. Of course that human CO2 contributes to Global Warming, we know this from Arrhenius times. The discussion arise when we try to quantify the warming, and in that direction we have advanced little over the last thirty years, in terms of empirical evidence.

    Well, I mean "catastrophic" in the sense of need to scare people. And there is no need without empirical evidence.

    There is no basic misconception, CO2 concentrations are important for life not only in the terms you are pointing at, but also in absolute value. Both sides should be taken into account. And 400 ppm is only round number, nothing else.

  46. Empirical evidence that humans are causing global warming

    Eclectikus, no comprehensive counterargument that accounts for physics and observations has been offered by anyone.  No matter what other forcing is discovered, the enhanced GHE must be accounted for.  It's power is well-demonstrated to be within a range that would make it the dominant forcing of the last fifty years.  Solar variation (orbital + output) is the only other comparable forcing, and it has been flat or falling for fifty years.  

    As far as "catastrophic" is concerned, you're going to have to provide a definition.  Everyone who uses the word seems to have a different definition.  Some people even like to define it differently for different rhetorical objectives.  Also, you are under a basic misconception: the absolute ppm for CO2 is not the issue re extinction.  The issue is the rate of increase and the resulting rate of increase in global energy storage.

  47. Empirical evidence that humans are causing global warming

    If the avg temp of the moon is -36 C ((100 + -173)/2), why doesn't physics tell us that without an atmosphere the earth's temp wouldn't also be -36 C?  Something is missing from the presentation. 

  48. Empirical evidence that humans are causing global warming

    Just one straw man more, any skeptic would agree with the title of this post. What most skeptics thinks is that:

    - There are no empirical evidence that humans are the main factor caused the global warming of the second half of pass century.

    - There are no empirical evidence of that this small anthropic component global warming might become catastrophic, rather the opposite.

    And there isn't.

    Too much CO2 in the atmosphere? Come on, we are closest to the minimum needed for life existence (150 ppm?) that of where we are now from the real value of worries about extinctions (1000 ppm?). Try this.

  49. Empirical evidence that humans are causing global warming

    guinganbresil - In anticipation of possible comments (having Googled SkS for previous discussions on the subject and your comments), I will note that cloud changes would be a feedback to temperatures, not a forcing, and that despite attempts to show negative cloud feedback by Lindzen and Choi 2011, or Spencer and Braswell 2011, the evidence indicates that any such cloud feedback would be small and likely positive (as per Dessler 2011). 

    Spectral reductions in effective emissivity are indeed direct evidence for an enhanced greenhouse effect. 

  50. Empirical evidence that humans are causing global warming

    stbloomfield, yah I'd agree with that.  Gpwayne probably didn't address it because for people who have been around the science for a while, the anthro element is bat-upside-the-head obvious.  Also, SkS regulars sometimes forget that not everyone looks through the whole (or even 1/100th of) site before commenting.  It's now huge.

    Moderator Response:

    [GPW]. I think the issues raised merit further consideration, but can I also point out that we're reading this rebuttal out of context - as a stand-alone post. Its primary use is as part of the multi-level rebuttal here:

    http://www.skepticalscience.com/empirical-evidence-for-global-warming-intermediate.htm

    It strikes me that the discussion has been of an intermediate level, while the rebuttal is rather more basic. In context, the issues raised may be addressed in the intermediate version, which in context is only a tab away.

    Writing the basic level rebuttals always involves some compromise. They are circulated to many working scientists and science professionals for comment and approval prior to publication, and many who review the work want something added, some clarification, some elaboration. Of course, if we accomodated all the suggestions, the rebuttal would no longer be basic. 

    It seems that writing about science for the general public requires some compromises that will always be a little unsatisfactory. But thanks for all the constructive criticism. I'll have a think about them and see if I can improve the text.

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