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Thread: Climate Change / Global Warming Discussion

  1. #2011
    Member tigerade's Avatar
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    Quote Originally Posted by dhrivnak View Post
    Tigerade; by chance do you have any good links or references on the Climate Sensitivity? In reading about WSJ piece from Judith Curry about relatively low climate sensitivities My WSJ op-ed: Global warming statistical meltdown | Climate Etc..

    It seems to me that their analysis using the low ends of input reference temperatures and lowering "normal" probability levels to 17%-83%, and only looking out 70 years their paper says we should remain under the 2 degree alarm point if we double CO2. I know that is a lot of assumptions but I have not found many good papers on what the expected sensitivity is. Do you have any suggested links.

    Thank you.
    Sorry for the slow response, crazy busy week for me. There is considerable uncertainty over how much the climate will warm if CO2 levels are doubled from per-industrial levels, which at this point they almost certainly will be. Notice that I said that there is uncertainty over how much warming, not whether or not there will be warming. So when you ask about climate sensitivity, you'll always get an answer that is in a range. It's also important to note that the word "uncertainty" in this case does mean range.

    Back in the 1890's, Arrhenius predicted about 5-6 degrees of warming if carbon dioxide levels were doubled:
    The History of Climate Science

    Through further work Arrhenius determined that if you halved the amount of atmospheric carbon dioxide, the temperature of Europe could drop by as much as 4-5C. But could such a change, big enough to cause an ice age, occur? He turned to colleague Arvid Hogbom (1857-1940), who had been investigating natural carbon dioxide cycles, to see if it could. Hogbom had, at the time, started to consider carbon dioxide emissions from factories (simple enough if you know, for example, how many tons of coal each factory burns a year). He had been surprised to find that man-made emission rates were very similar to those occurring in nature. Back in the 1890s, that of course represented a tiny fraction of the fossil fuels that we burn today; but what, they asked themselves, might happen if mankind burnt ever-increasing amounts over many centuries? Side-tracking from the ice-age research, Arrhenius ran calculations to see what a doubling of carbon dioxide levels might do to temperatures. He came up with an answer of 5-6C of warming as a globally-averaged figure.

    Back then, at 1890s burning-rates, they didn't see this as a problem: firstly at those rates it would take thousands of years for the doubling to take place and secondly the oceans were thought to be able to absorb five-sixths of the emissions. By the time the hypothesis appeared in a popular book that was published in 1908, the burning-rate had already gone up significantly, so in accordance with that change they revised the doubling-time down to a few centuries, but it was still something of a scientific curiosity, the stuff of after-dinner conversations.
    Of course, Arrhenius had the disadvantage of working with late 19th century technology. This changed when Dr. Gilbert Plass released the paper in the 1950's: "The Carbon Dioxide Theory of Climatic Change"
    The Carbon Dioxide Theory of Climatic Change - PLASS - 2010 - Tellus - Wiley Online Library

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    By the mid-1950s, scientists had the huge advantage of the calculating power of computers. This made it possible to dissect each layer of Earth's atmosphere and work out how it might absorb infra-red radiation. Physicist Gilbert Plass undertook the task: firstly his work (published as a paper entitled The Carbon Dioxide Theory of Climatic Change, in the journal Tellus in 1956) confirmed that more carbon dioxide would have a warming effect and secondly that doubling levels of that gas would result in a warming of 3-4C. That, at mid-1950s emissions rates, would be a rise of around 1.1C per century. Plass wrote that if at the end of the 20th Century the average temperature had continued to rise, it would be "firmly established" that carbon dioxide could cause climate change. But again, the response was luke-warm. The lack of attention to water-vapour and cloudiness led to criticisms of crudeness, and again the matter of the ocean absorbing the extra gas was raised in objection to Plass' suggestion that the extra carbon dioxide would remain in the atmosphere for a thousand years
    Ok, so now I'm sure your question is that "Well that's what the calculations were in the 1890's, 1950's, but what about today?". Good question. Here is a 2008 paper.

    http://www.iac.ethz.ch/people/knutti...ti08natgeo.pdf

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    This is complex stuff, and I don't dare claim to be an expert. However, this SKS article gives a good explanation of our knowledge about climate sensitivity:

    How sensitive is our climate?

    Climate sensitivity is the estimate of how much the earth's climate will warm in response to the increased greenhouse effect if we double the amount of carbon dioxide in the atmosphere. This includes feedbacks which can either amplify or dampen that warming. This is very important because if it is low, as some climate 'skeptics' argue, then the planet will warm slowly and we will have more time to react and adapt. If sensitivity is high, then we could be in for a very bad time indeed. There are two ways of working out what climate sensitivity is. The first method is by modelling:
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    Climate models have predicted the least temperature rise would be on average 1.65C (2.97F) , but upper estimates vary a lot, averaging 5.2C (9.36F). Current best estimates are for a rise of around 3C (5.4F), with a likely maximum of 4.5C (8.1F). The second method calculates climate sensitivity directly from physical evidence, by looking at climate changes in the distant past:

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    These calculations use data from sources like ice cores to work out how much additional heat the doubling of greenhouse gases will produce. These estimates are very consistent, finding between 2 and 4.5C global surface warming in response to doubled carbon dioxide.

    [top]Its all a matter of degree

    All the models and evidence confirm a minimum warming close to 2C for a doubling of atmospheric CO2 with a most likely value of 3C and the potential to warm 4.5C or even more. Even such a small rise would signal many damaging and highly disruptive changes to the environment. In this light, the arguments against reducing greenhouse gas emissions because of climate sensitivity are a form of gambling. A minority claim the climate is less sensitive than we think, the implication being we dont need to do anything much about it. Others suggest that because we can't tell for sure, we should wait and see.
    In truth, nobody knows for sure quite how much the temperature will rise, but rise it will. Inaction or complacency heightens risk, gambling with the entire ecology of the planet, and the welfare of everyone on it.

  2. #2012
    Senior Member dhrivnak's Avatar
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    Thank you very much Tigerade. This is perfect. Now to get the masses to understand.

  3. #2013
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    Saw this as a commercial before movie previews at the theater (saw Gone Girl - good movie) and was shocked to see it in such a public place, but glad it's getting play time. I think it's put together quite well and I love the angle they are using.

    Harrison Ford is The Ocean €” Nature is Speaking

    They have several other videos from - Julia Roberts, Kevin Spacey, Edward Norton, Penelope Cruz, and Robert Redford.

    Nature Is Speaking
    Last edited by ggies07; 2014-10-18 at 03:36 PM.

  4. #2014
    Junior Member James Anders's Avatar
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    Currently own 2013 Subaru BRZ and 1992 Acura NSX

  5. #2015
    Member tigerade's Avatar
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    Hal Lewis is no longer alive. This letter is 4 years old. Also, Dr. Lewis was an expert in nuclear physics. That does not make him a climate scientist and I am not aware of any peer-reviewed research Dr. Lewis has published on climate. There is nothing wrong with being an expert in nuclear physics, but that doesn't make you an expert in climate.

    Scientists are not like "Brains" in the show "Thunderbirds":
    9. Climate Change - Meet the Scientists - YouTube

    Also, there was nothing in the letter that addressed the physics of heat-trapping gases or how climate changes. The whole thing read as an opinion piece, and that's because it was an opinion piece. A vitriolic attack on the APS, and if he was so adamant that APS was being paid off by someone then why did he not provide any specific examples? When I say that organizations like Heartland Institute receive money from the fossil fuel industry, I can provide specific documents to that being the case. It would have been wonderful for Dr. Lewis to have done the same.

    And if he thought that "ClimateGate" was evidence against global warming, then he must be joking:

    6. Climate Change -- Those hacked e-mails - YouTube
    7. Climate Change - e-mails and science censorship - YouTube
    8a. Climate Change - Phil Jones and the - YouTube

    And see the APS response here:

    October 12, 2010

    WASHINGTON, D.C. — In a recent letter to the American Physical Society (APS) President Curtis A. Callan, chair of the Princeton University Physics Department, Harold Lewis, emeritus physics professor at the University of California, Santa Barbara, announced that he was resigning his APS membership.
    In response to numerous accusations in the letter, APS issues the following statement:
    There is no truth to Dr. Lewis’ assertion that APS policy statements are driven by financial gain. To the contrary, as a membership organization of more than 48,000 physicists, APS adheres to rigorous ethical standards in developing its statements. The Society is open to review of its statements if members petition the APS Council – the Society’s democratically elected governing body – to do so.
    Dr. Lewis’ specific charge that APS as an organization is benefitting financially from climate change funding is equally false. Neither the operating officers nor the elected leaders of the Society have a monetary stake in such funding. Moreover, relatively few APS members conduct climate change research, and therefore the vast majority of the Society’s members derive no personal benefit from such research support.
    On the matter of global climate change, APS notes that virtually all reputable scientists agree with the following observations:

    • Carbon dioxide is increasing in the atmosphere due to human activity;
    • Carbon dioxide is an excellent infrared absorber, and therefore, its increasing presence in the atmosphere contributes to global warming; and
    • The dwell time of carbon dioxide in the atmosphere is hundreds of years.

    On these matters, APS judges the science to be quite clear. However, APS continues to recognize that climate models are far from adequate, and the extent of global warming and climatic disruptions produced by sustained increases in atmospheric carbon loading remain uncertain. In light of the significant settled aspects of the science, APS totally rejects Dr. Lewis’ claim that global warming is a “scam” and a “pseudoscientific fraud.”
    Additionally, APS notes that it has taken extraordinary steps to solicit opinions from its membership on climate change. After receiving significant commentary from APS members, the Society’s Panel on Public Affairs finalized an addendum to the APS climate change statement reaffirming the significance of the issue. The APS Council overwhelmingly endorsed the reaffirmation.
    Lastly, in response to widespread interest expressed by its members, the APS is in the process of organizing a Topical Group to feature forefront research and to encourage exchange of information on the physics of climate.

  6. #2016
    Senior Member Raffy.Roma's Avatar
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    @James

    Robert asked us always to make some comments when reporting an article in this thread.
    PLEASE NOTE: Posts are the copyrighted intellectual property of the author and are intended as part of a conversation within this forum. My words may NOT be quoted outside this forum without my expressed consent.

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