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Climate Hustle

Empirical evidence for positive feedback

Posted on 30 November 2007 by John Cook

In our recent post on model uncertainty, we found uncertainty is skewed towards higher climate sensitivity (and hence greater temperature change). However, this is based on the assumption that the climate system has net positive feedback. Do empirical observations confirm the existence of positive feedbacks - and more importantly, a net positive feedback?

Water Vapour as a positive feedback

Water vapour is the largest positive feedback in our climate system. The amplifying effect of water vapor is detected in Soden 2001 which observed the global cooling after the eruption of Mount Pinatubo. The cooling led to atmospheric drying which amplified the temperature drop.

Satellites have observed an increase in atmospheric water vapour by ~0.41 kg/m² per decade since 1988. A detection and attribution study (Santer 2007) found the primary driver of 'atmospheric moistening' was the increase in CO2 caused by the burning of fossil fuels. More on water vapour...

Carbon cycle feedback

That CO2 lags temperature is a popular skeptic argument but the implications are often overlooked. If rising temperatures lead to more CO2 outgassing from the oceans and other sources, that means current global warming will lead to more CO2 being released, amplifying the warming. While the mechanisms are not fully understood, the amount of CO2 change from changing temperatures and subsequent feedback have been observed in ice core records. Torn 2006 looks at the last 360,000 years and finds a warming of 1.5–4.5°C is amplified by CO2 feedback to 1.6–6.0°C. Scheffer 2006 focuses on the Little Ice Age, from 1500-1600 AD and estimates CO2 feedback will amplify warming by an extra 15 to 78%. More on CO2 lag...

The ocean's diminishing ability to absorb CO2

While the ocean absorbs around half of human CO2 emissions, observations indicate the oceans are losing their ability to absorb CO2. Quéré 2007 found the Southern Ocean has reached its saturation point, diminishing its ability to absorb more CO2. Similarly, CO2 absorption by the North Atlantic has dropped even more dramatically, halving over the past decade (Schuster 2007). If this trend continues, it potentially leads to a positive feedback where the oceans take up less CO2 leading to CO2 rising faster in the atmosphere. More on the carbon cycle...

Plankton growth slowing

Microscopic ocean plants called phytoplankton account for about half the transfer of carbon dioxide (CO2) from the environment into plant cells by photosynthesis. Land plants pull in the other half. However, warmer water creates more distinct ocean layers and limits mixing of deeper nutrient-rich cooler water with warmer surface water. The lack of rising nutrients keeps phytoplankton growth in check at the surface. Satellite observations of plankton growth have observed the rate at which plant cells take in CO2 has declined more than 6 percent globally over the last two decades (Gregg 2003).

Arctic sea ice melt

As Arctic sea ice melts, more ocean is exposed. Sea water is more effective at absorbing sunlight than ice which reflects sunlight back into space. Hence as sea ice melts, temperatures rise which causes more melt and so on. Arctic sea ice loss has not only has exceeded IPCC model projections - it has fallen below even the extreme lower limit of predictions (Stroeve 2007).

Melting Permafrost

The Arctic permafrost contains more carbon locked away in frozen soil than the entire atmosphere (Zimov 2006). On top of this, thawed permafrost can release its carbon as methane, 20 times as potent a greenhouse gas as carbon dioxide. Methane has been observed to be bubbling from Siberian thaw lakes five times higher than previously thought (Walter 2006).

Melting snow cover extent

A study on Northern Hemisphere snow cover extent over the period 1972–2006 (Déry 2007) found significant declines in snow cover during spring over North America and Eurasia. It also found an enhanced snow-albedo feedback over northern latitudes that acts to reinforce initial warming. Eg - as the snow melts, the ground and sea absorbs more warmth from the sun.

Putting it all together - climate sensitivity

While empirical observations confirm the existence of distinct positive feedbacks, the crucial question is what is the net positive feedback? Another way of asking this is what is climate sensitivity? Climate sensitivity is typically defined as the amount of temperature change for the doubling of atmospheric CO2. If there was no net positive feedback, climate sensitivity would be around 1°C. A number of studies calculate climate sensitivity directly from empirical observations, independent of models.

  • Hansen 1993 looks at the last 20,000 years when the last ice age ended and calculates a climate sensitivity of 3 ± 1°C.
  • Lorius 1990 examined Vostok ice core data and calculates a range of 3 to 4°C.
  • Hoffert 1992 reconstructs two paleoclimate records (one colder, one warmer) to yield a range 1.4 to 3.2°C.
  • Gregory 2002 used observations of ocean heat uptake to calculate a minimum climate sensitivity of 1.5.
  • Tung 2007 performs statistical analysis on 20th century temperature response to the solar cycle to calculate a range 2.3 to 4.1°C.

So climate sensitivity is around 3°C. The warming from a doubling of CO2 amounts to around 1°C with positive feedbacks contributing another 2°C of warming. More on climate sensitivity...

UPDATE 5 Apr 2008: Tamino gives a good overview of feedbacks, both positive and negative.

UPDATE 22 Apr 2008: there is new evidence that the Arctic floor is thawing and releasing methane

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Comments

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Comments 51 to 83 out of 83:

  1. "On the other hand, carbon dioxide emits heat radiation to space. In the stratosphere this emission becomes larger than the energy received from below by absorption. "

    You don't have that information. Certainly not from that graph.
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  2. My point Phillipe is that the assumption that warming would cause more economic hardship than benefit is not at all evident from the historical or the archeologic record. The assumption made above my comment was that warming would have overwelmingly negative impacts. I find that unlikely to say the least. Your counter examples are also regional and focus on inadequate rainfall.

    To get any net negative economic effect you have to assume that there will be some significant regional changes in rainfall and that the changes will produce negative effects. For example that deserts would expand more than arable land elsewhwere would grow. That is already a mighty long and unlikely string of assume.
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  3. From reading your posts, it is obvious that I understand these things much better than you, GMB. You should shoulder the money to actually get that paper from AGU, it's not that expensive and you might actually understand something, provided you can focus your attention long enough to read it.

    I understand your point, WA. There are a lot of unknowns in this issue. The historical and archaeologic records apply to periods during which the human population was a tiny fraction of what it is now and what it will be in 2040. Thus, its usefulness has limitations.

    For myself, I am skeptical of catastrophic scenarios, but I do not see any reason to believe that there will be more benefit than hardship either. Any change requiring "geographic" adaptation will run into geopolitical considerations that have no comparison in history (esp. for the number of people involved). Furthermore, you don't really know how unlikely the adverse changes you mentioned actually are.

    There are also other considerations. Oil just hit $100/barrel. How high will it go? With China and India increasing their oil consumption at an enormous pace, what is the chance that other countries that are lagging will ever be able to afford any oil? What will be the price of a barrel in 20 years? Even if reserves are found and exploited in the Arctic, and the shales are sqeezed to the last drop all over the world, is there any possibility that 9 billion people can live like us now for any length of time?
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  4. Oil will go a lot higher. The price will go up soon, often and by large margins. The only thing which might delay this is an American recession which appears to be happening even now. Oil will keep going up because the normal market corrections have been hampered by this science fraud. Since the science fraud that this "global warming" racket involves is part of a wider energy-deprivation-crusade.

    We would by now be bristling with nuclear power reactors and coal-liquification plants. "Peak Oil" would have been a concept with some predictive value but it would have been nothing that need concern the public since substitution towards liquified coal would have begun many years ago.

    This Malthusian/Marxist racket, posing as science, though oddly incapable of finding evidence for itself, has already slaughtered people by the millions insofar as it bureaucratised DDT. Over at Tim Lamberts site they are voicing their grave opposition to malaria eradication. This is a poisonous movement and these are very sick sick people.

    Dude if you knew more than me you'd just explain the diagram. What we see is that its no evidence for anything. It won't even tell you the time period involved. No evidence has been presented that CO2 is cooling the stratosphere. For that we would need to have something similiar that was working over a number years giving enough time for the CO2 level to change.

    Also we would need something which went out of its way to show both incoming and outgoing absorption. Not just pick out the 15 microns and ignore the other parts of the absorption spectrum.

    Now have you got any evidence that CO2 is warming anything globally?

    We've got to have everyone admit they were wrong so we can get this energy production off the ground.
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  5. "My point Phillipe is that the assumption that warming would cause more economic hardship than benefit is not at all evident from the historical or the archeologic record."

    Thats totally understating the matter. Don't softpedal these lunatics. The historical and archeological record speaks with one voice on the matter.

    But its not a question of WARMING VERSUS COOLING. Its a question of whether the extra CO2 will mitigate the natural cooling.

    The idea that extra CO2 will cause net economic costs is self-evidently ludicrous. And we have to come down on these science fraudsters with extreme predjudice.

    Don't pussyfoot around with these people WOL. They ARE charlatans. You know enough to know that the warm times are always the good times and the times with good rainfall.

    Whereas the Cold times are all about extreme weather events and drought.
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  6. We might compare the campaign to restrict industrial-CO2-release to the book of Mormon.


    http://www.youtube.com/watch?v=G1mFdO1wB08&feature=related

    No archeological support can be found for the Book Of Mormon. The events within it leave no remnants of the technology, coinage, animals or plants that are talked about within it.

    Yet the Mormons still go in for this crap.

    Same goes here. No evidence whatsoever has been found in support of the contention that industrial-CO2-release ought to be restricted.

    But these alarmists, far worse and more harmful nutters than Mormoms, continue to go in for it anyway.

    Now French fellow. Do you have that evidence or not?

    Come up with the evidence or admit you are wrong.
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  7. Here is another interesting piece of evidence, measuring escaping long wave radiation:
    Abstract: "Here we analyse the difference between the spectra of the outgoing longwave radiation of the Earth as measured by orbiting spacecraft in 1970 and 1997. We find differences in the spectra that point to long-term changes in atmospheric CH4, CO2 and O3 as well as CFC-11 and CFC-12. Our results provide direct experimental evidence for a significant increase in the Earth’s greenhouse effect that is consistent with concerns over radiative forcing of climate."

    Harries et al, Increases in greenhouse forcing inferred from the outgoing longwave radiation spectra of the Earth in 1970 and 1997, Nature. 2001 Mar 15;410(6826):355-7
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  8. So whata are they saying here. The oceans are a great deal warmer then in 1970 and they ought be releasing a lot more energy. Its not good enough to make the claim that things have changed due to industrial-CO2 without actually demonstrating this.

    How are they backing the claim up?

    Don't be calling it MORE EVIDENCE when you didn't have any evidence in the first place and are yet to show why this latest is evidence.
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  9. What are they saying there? It's really obvious: more heat is retained. They measured how much. The heat is retained in the bands of the gases mentioned and consistent for each with the increased concentration of the gas, also measured.

    You can make the claim that additional heat retained will not affect the climate. I find it a less plausible claim than the opposite.
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  10. OK, after reading through this series of posts I am convinced that Philippe is a saint and empowered with superhuman patience (and GWB, I have read the paper the Philippe links to in post #57 and as far as I can tell, your comment does not make sense).

    Philippe: . Here is another paper that presents an interesting result: It is not without its problems (one of which is the command of the English language) but it does a good job of measuring a very difficult quantity.

    I wanted to pick up a earlier thread about CO2 fertilization. There is a lot of misconception regarding CO2 fertilization. First, we need to recognize that there are two main types of plants that use carbon in a different manner – C3 and C4 plants. The C4’s are more efficient at using CO2 and thus elevated levels do not do them much good. Now, most of the plants are C3s but some of our most important commercial crops (e.g. sugarcane and corn) are C4s.

    In the C3 case, the main benefit from CO2 is that the plants are able to survive better in water stressed areas. If there is more CO2, the leaf stomata can close more and prevent transpiration.

    However, in regards to additional growth from CO2 fertilization, this is a good thing if you are trying to grow flowers or perhaps raise oranges. But enhanced CO2 growth is a problem because the nutritional density is changing (nutrition is primarily based on nitrogen, so more CO2 doesn’t do much good). So in fact an animal has to eat more of the material to get the same nutrition.

    John Cook - Sorry if I am repeating the stuff that you already have on here - I didn't have a chance to research. Busy times here and all!

    Regards,
    John Cross
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  11. You're too kind, John. I did lose it at some point, but nothing like the verbal assault I had to endure could have justified. All that stuff was edited (although I'm glad the fiat lux comment was kept, it is kinda funny). The paper you linked looks might interesting, thanks for that.
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  12. Look Phillipe. If the oceans had accumulated greater heat and were radiating out greater heat....... Its obvious that this in itself would give the result that you see.

    For Petes sakes man. Its like you cannot seem to grasp the obvious.
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  13. I think its time to remind people of the theses for which we need to find evidence for.

    1. Have we any evidence for the likelihood of catastrophic warming?

    2. Have we any evidence that suggests that a little bit of human-induced warming IS A BAD THING during a brutal and pulverising ice age?

    3. Have we any evidence that industrial-CO2-release is BAD for the environment when so far its wall-to-wall evidence that it enhances the biosphere.

    4. Do we even have any real evidence that the extra industrial-CO2-release heats up the planet on a global level in any substantial way?

    So far the science tells us that there is simply no chance of catastrophic warming since we live on a planet with a one-way catastrophic cooling bias.

    So far the science tells us also that industrial-CO2-release is good for man and the environment.

    These two propositions are so uncontested by the scientific evidence that this movement is shown to be an obvious malevolent and repulsive fraud.

    >>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>>

    So where is the evidence that goes contrary to all this? No-ones got it and they are all bullshitting about it.

    Now about this new study which this Frenchman has failed to link. Here we see no attention to inward absorption whatsoever. Thats a total gyp right there. Only outwards absorption is even so much as considered. Only looking at one side of the income statement. This despite the fact that two out of the three spectra that CO2 absorbs are not relevant to outward absorption and ought to be more relevant to blocking inwards absorption for a planet at our current temperature.

    What we see in the study is nothing new at all. What did we EXPECT from such a study?

    WHAT WOULD WE HAVE EXPECTED IN ADVANCE FROM SUCH A STUDY?

    If there is more of some gasses we would expect them to be absorbing a little more of the outwards radiation (and the inwards radiation too for that matter). Did we find this? Yes we did, big deal.

    And if the oceans have accumulated more heat energy since 1970 we would expect the amount that these gasses are absorbing to be greater again to reflect this accumulated heat energy.

    Did we find this? Yes we did big deal.

    But did we find anything to contradict the actual hypotheses we are trying to refute or add credence to?

    Now we didn't. So the science-fraud remains the same.
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  14. So if the oceans were radiating greater heat, you'd see less heat radiating out to space? That makes perfect sense in your mind I'm sure.
    Do you even read what you post? you make no sense whatsoever. What is relevant pertains to heat, LW radiation. I did post the link to that paper. Your abusive language and your incoherence speak volume. If you did not appear to be also relatively simple, I'd say you're a mole trying to discredit the all skeptic side. Enjoy the ranting, I have better things to do than read your delirium.
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  15. No if the oceans were radiating greater heat you'd see a more active absorption in the bands of greenhouse gasses present. Which is what you have seen is it not?

    Your jumper works better if you aren't suffering hypothermia already. Same principle.
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  16. You haven't posted a link.

    But in any case what I want to see is some plausible evidence in the first place.

    I cannot see how this CO2 would be all that relevant unless it was so abundant as to increase substantially air pressure or we are talking about the planet being so hot as make the other two absorption spectrum relevant…..

    …. or again so cold as to make the first absorbtion region more relevant.

    Its not really anything much of a greenhouse gas for this planet once the early work has been done to get the planet above 0 degrees Celsius.

    And yet those with a contrary view don’t bother showing why it is that they take this view from first premises.

    They certainly don’t disaggregate matters for the different parts of the earths surface or yet even for the different times during the day.

    Once we ignore the phrase “greenhouse gas” and disaggregate the specific absorption regions of CO2 we find that these energy-deprivation-crusaders don’t even have the beginnings of a case.

    Can anyone come up with even so much as the beginnings of plausibility to this this global warming racket SPECIFICALLY WITH REGARDS TO THE THREE ACTUAL ABSORPTION SPECTRA OF CO2.

    Now are any of you able to make that case?

    The absorption spectra of OZONE is just right to heat up the earth so long as we could get heaps of ozone actually at surface level. Which would of course be poisonous.

    But what I’m saying is that the light frequency of the area that OZONE absorbs at is far more relevent to the temperature coming off the earths surface.

    But 2 of the three absorption regions for CO2 are just not relevant at all for Earth. For Venus yes. But not for earth except to block incoming.

    And the one that is relevant is more relevant for heating the earth above zero. Not for heating it above where it is now.

    At least thats what it looks like to me. But I cannot find any of these fraudsters making the case from the ground up.

    Its hard enough to get them to make any sort of scientific case. They prefer to talk about whether to destroy the economy in its entirety, or whether to force multi-billions of costs upon us in terms of carbon sequestration.
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  17. Hi John,

    It's generally agreed that 1° increase would occur from a doubling of CO2 alone.

    What most of the best skeptic arguments hinge on is questioning how much additional forcing is caused through feedbacks? If CO2 ppm are 3/4's of the way to doubling and we haven't experienced a 2.5° - 3.0° temperature increase then it invites the question as to whether these projected feedback loops are as intense as modeled or perhaps there are counterveiling phenomena.

    Likewise skeptics cite the differential between temperature anomalies in the Northern vs. Southern hemispheres and the closer correlation with aerosols. Since August 2007 V. Ramanathan has authored papers citing mid-to-upper tropospheric soot as having:

    - 50% role in heating over the Indian ocean, half of what's ascribed to CO2
    - 40% role in atmospheric heating globally

    Ramanathan is quite blunt in stating that this was contrary to the conventional wisdom that soot's heating effect was counterbalanced by other aerosols as well as its own shading effects. Wouldn't that impact the role of CO2 in general climate models?

    Others have likewise has found soot-fall to be particularly pernicious on the ground, with soot causing up to 90% of the Arctic melt-off, industrial soot having an 8x more powerful warming effect on snow and ice than that from wood fuels. Significantly, Hansen cites 25% of centennial global warming being due to the general Arctic melt-off.

    None of these statements seek to exculpate CO2, but it draws into question the margin of warming that CO2 is in fact responsible for. Surely Ramanathan's and Hansen's findings are reputable and yet they seem to me to weaken the brief for dangerous CO2-driven global warming.

    Best regards,

    /leebert
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  18. Hi John,

    It's generally agreed that 1° increase would occur from a doubling of CO2 alone.

    What most of the best skeptic arguments hinge on is questioning how much additional forcing is caused through feedbacks? If CO2 ppm are 3/4's of the way to doubling and we haven't experienced a 2.5° - 3.0° temperature increase then it invites the question as to whether these projected feedback loops are as intense as modeled or perhaps there are counterveiling phenomena.

    Likewise skeptics cite the differential between temperature anomalies in the Northern vs. Southern hemispheres and the closer correlation with aerosols. Since August 2007 V. Ramanathan has authored papers citing mid-to-upper tropospheric soot as having:

    - 50% role in heating over the Indian ocean, half of what's ascribed to CO2
    - 40% role in atmospheric heating globally

    Ramanathan is quite blunt in stating that this was contrary to the conventional wisdom that soot's heating effect was counterbalanced by other aerosols as well as its own shading effects. Wouldn't that impact the role of CO2 in general climate models?

    Others have likewise has found soot-fall to be particularly pernicious on the ground, with soot causing up to 90% of the Arctic melt-off, industrial soot having an 8x more powerful warming effect on snow and ice than that from wood fuels. Significantly, Hansen cites 25% of centennial global warming being due to the general Arctic melt-off.

    None of these statements seek to exculpate CO2, but it draws into question the margin of warming that CO2 is in fact responsible for. Surely Ramanathan's and Hansen's findings are reputable and yet they seem to me to weaken the brief for dangerous CO2-driven global warming.

    Best regards,

    /leebert
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  19. "It's generally agreed that 1° increase would occur from a doubling of CO2 alone."

    Both the skeptics and most of the alarmists make this claim. But its a totally dubious and unscientific claim for starters.

    It appears to assume that the molecules in the air are totally static. It assumes that pockets of molecules won't move upwards as a result of being warmer than the molecules around them.

    This one degree increase is a flat earth calculation. Its as if the sun is twice as far away, the earth is flat, and its always noon and so the whole flat world is the equator.

    It also takes no account whatsoever of imbedded energy in the oceans or in the entire planet.

    Everything is wrong with this assumption. Everything about this assumption is unscientific. So this particular paradigm isn't getting past its first assumption.

    But it just gets worse from there. Because while on the instantaneous level water vapur is a greenhouse gas.... What the water vapour is really doing is conveying energy out into space. So anyone not taking a mentally deranged instantaneous snapshot of the matter will realise that resultant increased water vapour is a negative, rather than a positive feedback scenario to whatever the CO2 is going to do.

    The process of wind whipping along the ocean and creating water vapour is a process of REFRIGERATION.

    This is why this pandemic of lying continues. Because the skeptical side of the argument knows that the other guys are wrong since thats what the empirical evidence says. But the situation can't progress, because the political motivation of the committed leftist liars has so "polluted the air" as it were, that no-one will dare putting up alternative paradigms to the hairbrained standard model.
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  20. what a joke this site is --why bother to read it
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  21. you have already decided on the ANSWER,,,then you have a ,6 grade mentality pretend to discuss it all as suposedly free discussions,,but you leave the intelligent posters out
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  22. Re # 68

    leebert, the pre-industrial atmospheric CO2 concentration was around 280 ppm, and we're at ~ 386 ppm. So we're only just over a third of the way towards doubling. Not 3/4's of the way!

    It's straightforward to calculate the temperature rise at equilibrium predicted from a rise of CO2 from 280 ppm to 386 ppm, assuming a climate sensitivity of 3 oC temperature rise per doubling of atmospheric CO2. This is near 1.4 oC.

    Since we're pumping CO2 into the atmosphere far faster than the earth can come to thermal equilibrium with the new forcing (from 386 ppm of CO2 and rising), we still have quite a bit of warming "in the pipeline" even if the atmospheric CO2 levels were to stop dead at 386 ppm. We've had around 0.8-0.9 oC of warming so far. We have another 0.5-0.6 oC in the pipeline.

    So the warming since the pre-industrial era is consistent with a climate sensitivity near 3 oC.

    One of the worrying things highlighted by Ramanathan is that the large mass of atmospheric man-made aerosols is protecting us somewhat from the full effect of our raised greenhouse gas levels. In other words we might have a bit more than 0.5-0.6 oC of warming "in the pipeline", which would indicate that the climate sensitivity is somewhat above 3 oC of warmning per CO2 doubling. As Ramanathan has argued, while it would be nice to rid the world of the brown cloud aerosol contribution which has a net warming effect, the total aerosol effect is a cooling one, and it's difficult to see how one could specifically eliminate brown clouds which tend to arise as a result of generalised aerosol formation.
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  23. re 72...recent research has shown cloud cover is affected by natural aerosols emitted by plants. See comments on the "It's aerosols" thread.
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  24. Well, I couldn't find the appropriate thread, so here's an animation film I've just discovered from Leo Murray, about AGW and the 'tipping point': "Wake Up, Freak out - then Get a Grip"

    Is it accurate with climate science in general, and especially Hansen theory ?
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  25. This can't be good.

    Thawing permafrost will accelerate global warming in decades to come, says new study

    One- to two-thirds of Earth’s permafrost will disappear by 2200, unleashing vast quantities of carbon into the atmosphere, says a study by researchers at the Cooperative Institute for Research in Environmental Sciences (CIRES) National Snow and Ice Data Center (NSIDC).

    “The amount of carbon released is equivalent to half the amount of carbon that has been released into the atmosphere since the dawn of the industrial age,” said NSIDC scientist Kevin Schaefer. “That is a lot of carbon.”
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  26. IIRC, 52 PPM by itself.

    Coupla beers ago I'd have actually looked it up. ;)

    The Yooper
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  27. Water vapor and CO2 'feedback' is miniscule. It takes 341.5 W/m^2 to produce no more than 1.1 W/m^2 of intrinsic effect. The additional effect from the CO2 'warming' is (1.1^2)/341.5 -> .0035 W/m^2, or mouse nuts. The same is true of water vapor, relative to GHG effects. Beside, the effects of GHG directly affect the system gain and not the feedback anyway.

    While there was some contraction of average N hemisphere snow/ice a few years ago, it represented a relatively small fraction of change, relative to the whole, moreover; S hemisphere ice was been growing at the same time.

    Alpine glaciers in the Sierra Nevada mountains have been growing for 3 consecutive years and this winter has seen record snow cover and cold over most of N America and Europe.

    Do the math folks. Consider how small these changes are relative to the peak extents of summer and winter. There's nothing at all unusual or unexpected about the direction, rate or magnitude of any changes we see.

    The most convincing empirical data is that without clouds, the global temperature would be higher owing to a lower albedo. Clouds provide the predominate feedback mechanism and the net effect of more clouds makes the surface cooler and makes the planet look colder from space (clouds are colder than the surface when seen from space). This manifests the clear signature of net negative feedback.
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    Moderator Response: [muoncounter] This thread is about evidence for feedbacks. Please see Are glaciers growing for evidence that they are not or to substantiate your claim. Please see A positive outlook for clouds for evidence that water vapor feedback is significant or to substantiate your claim. Please avoid rehashing discussions that already have long complicated threads unless there is some new published science or evidence on the topic.
  28. muoncounter,

    I know that the Sierra alpine glaciers are growing because my friends and I have been skiing them all summer for 20+ years and there's a clear progression from year to year. They grew for a while, shrank or stayed about the same for a decade and have started growing for the last 3 years and most likely again this year.

    As for positive water vapor feedback, this is absolutely incorrect when clouds are considered a water vapor influence. Look at the work of Spencer, Lindzen and others for more details, or just look at the actual data (instead of highly processed anomaly plots). Of course, this presupposes you have a strong background in thermodynamics, control theory and more, rather than just faith in another persons interpretation, This article claims empirical evidence supporting positive feedback, but the evidence cited is nothing more than unsupportable conclusions based on preconceived bisses.
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  29. co2isnotevil - Regarding cloud feedback, I suggest you look at (and comment upon) What is the net feedback from clouds, and in particular Clement et al. (2009). The data indicates that low level clouds are decreasing with warming, producing a positive feedback.

    Glaciers - 95% of the worlds glaciers are retreating. Perhaps you are skiing on one of the 5% that isn't? Projecting local conditions to global ones without supporting data is a common error.

    I'm not going to go into the water vapor and CO2 feedback claims you make, aside from noting that everyone in the field disagrees with you. This was more than sufficiently covered in overly long discussions here and here.
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  30. co2 "I know that the Sierra alpine glaciers are growing"

    Odd that there is no empirical scientific evidence to support this anecdotal evidence. In fact, there is quite a bit of evidence to the contrary:

    See this photo comparison from the Univ. of Portland:

    Comparisons of the repeat photography reveal that all ten of the glaciers have experienced a reduction in ice volume and surface extent over the past century.

    See also the 2009 report of the World Glacier Monitoring Service: all records for US glaciers in 2009 show mass loss. Are you perhaps confusing glacial movement with glacial growth?

    "Look at the work of Spencer, Lindzen and others for more details,"

    I seem to recall that we are still waiting for Spencer's 'magic clouds' to bring negative feedback to the rescue. Dessler and Sherwood 2009 have quite a different view on that feedback. See also Vavrus 2004:

    Compared with this fixed-cloud experiment, the simulated cloud changes enhance greenhouse warming at all latitudes, accounting for one-third of the global warming signal. This positive feedback is most pronounced in the Arctic, where approximately 40% of the warming is due to cloud changes. The strong cloud feedback in the Arctic is caused not only by local processes but also by cloud changes in lower latitudes, where positive top-of-the-atmosphere cloud radiative forcing anomalies are larger.

    Any further comments regarding cloud feedbacks, if any are still necessary, should go to the appropriate thread.
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  31. co2isnotevil@78
    Please provide some evidence to back up your assertions. Being dismissive and condescending does not add anything constructive to the discussion.
    0 0
  32. I just had a chance to review this entire thread, being inspired by chat mat who's mantra is: "there's no proof for CO2 driving global warming."

    I agree with John @60, Philippe is pretty near a saint for his repeated patient and info laden replies. I just wanted Philippe know that folks do read that stuff and his efforts are appreciated and helpful.
    ~ ~ ~ ~ ~ ~ ~

    #61 Philippe Chantreau at 12:18 PM on 10 February, 2008
    ". . . . (although I'm glad the fiat lux comment was kept, it is kinda funny)"
    ~ ~ ~
    Yes it was! [thumbs up smilie]
    ~ ~ ~ ~ ~ ~ ~

    #63 GMB at 14:36 PM on 10 February, 2008
    "So where is the evidence that goes contrary to all this? No-ones got it and they are all bullshitting about it."
    ~ ~ ~
    The problem with evidence is that until you decide to study it in good-faith it doesn't do you any good. The evidence is out there you just need to be willing to read it.
    0 0
  33. I would suggest that this page is updated with the newest research in this topic.
    0 0

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