[Vision2020] Climate Science: Introduction to Feedbacks: 150 Responses "...exactly the right level for interested laymen."
Paul Rumelhart
godshatter at yahoo.com
Sun Oct 10 21:32:39 PDT 2010
I've had a few life issues get in the way, but I'll respond to this
quickly. If you want me to show my work, I can do so. The IPCC reports
provide equations for estimating the radiative forcing for CO2. Change
in temperature for an increase in CO2 can be stated as the degree change
in temperature equals the radiative forcing in Wm^-2 multiplied by a
constant that is referred to as "climate sensitivity". In equation form
it's: dT = lambda * RF
Given a starting and ending CO2 value in parts/million, using the
equations given by the IPCC, you can determine the radiative forcing for
any increase in CO2 particulate count. (RF = 5.35 * ln (C / C0) is the
simplest one). Doing this, I get a value of 3.708 W/m^2. This agrees
with the IPCC values that I've seen lately.
That just leaves the sensitivity value (lambda). I've seen various
values used based on guesses about feedbacks (0.8 is common). But you
can calculate it yourself. You look at the temperature and CO2 ppm for
pre-industrial times (280ppm and 13.6C) and the temperature and CO2 ppm
today (385ppm and 14.5C) and you can calculate both the change in
temperature and the radiative forcing for those values and can compute
lambda based on those values. I did this and got a value of 1.516.
Multiplying the lambda value and the radiative forcing found earlier you
can calculate the expected temperature increase from pre-industrial
times to a doubling of CO2. I get approximately 2.2C. But this is the
increase from pre-industrial times, so if you subtract the temperature
increase we've already seen (0.9C) you get a value of 1.3C. This is
slightly higher than the 1.2C I've seen referred to elsewhere, perhaps
if I'd used one of the other equations provided by the IPCC (they had
four or five choices) I'd get that value.
This is usually just under the low end of the expected temperature
increases given by the IPCC, because all of the climate models assume
positive feedbacks will come into play and increase this number anywhere
from 1.5C to 6.5C or more.
Paul
Ted Moffett wrote:
> Please offer a reference from a credible peer reviewed science journal
> article that states that "No feedbacks, or balanced positive and
> negative feedbacks, mean warming of about 1.2C for a doubling of CO2
> from pre-industrial levels." The news article you offered as though
> it represented reliable science reporting states differently:
>
> http://www.chron.com/disp/story.mpl/nation/6841153.html
>
> "All agree concentrations of CO2 in the atmosphere are increasing, and
> there's a general agreement that a doubling of CO2 levels this
> century, by themselves, will produce an increase of 1.5 to 2 degrees
> Fahrenheit in global temperatures."
> ------------------
>
> Also, I'm puzzled why you write "It seems odd to me that more work
> wasn't done early on regarding
> feedbacks, since they are so critical to the question at hand."
>
> Climate feedbacks have been studied intensively for decades by climate
> scientists. Without an understanding of the dominant climate
> feedbacks, there would be no reliable basis for the conclusions of
> numerous major scientific organizations, that human increases in
> atmospheric CO2 are highly probable to dramatically alter climate. It
> appears you think you know more about this subject than the scientists
> involved with the National Academy of Sciences, or scientists at MIT
> (read MIT paper sourced lower down), who are taking human impacts on
> climate very seriously, as this NAS release states from May 19, 2010,
> regarding a series of reports on climate change:
> http://www8.nationalacademies.org/onpinews/newsitem.aspx?RecordID=05192010
>
> ----------------
> "My gut feeling is that since in the past CO2 levels have been much
> higher than they are now and the system didn't end up with boiling
> oceans or a snowball earth, that the idea of tipping points and
> runaway feedbacks is a fantasy."
>
> Regarding the preceding statement, to claim that because a snowball
> earth or boiling oceans from CO2 levels much higher than they are now
> did not occur in the past, that the idea of tipping points is a
> fantasy, is simply false. If inducing sea level to rise dramatically,
> as has occurred in the past linked to increased atmospheric
> CO2, involves a "tipping point," this is no fantasy. Consider the
> Paleocene-Eocene Thermal Maximum about 55 million years ago, when CO2
> levels were much higher, an Earth where there were little or no polar
> ice caps, and ocean levels were far higher. The following
> scientific article from "Nature" (
> http://es.ucsc.edu/~jzachos/pubs/Zachos_Dickens_Zeebe_08.pdf
> <http://es.ucsc.edu/%7Ejzachos/pubs/Zachos_Dickens_Zeebe_08.pdf> )states
> that "During the most prominent and best studied hyperthermal, the
> Paleocene-Eocene Thermal Maximum, ...the global temperature increased
> by more than 5 C. in less than 10,000 years. At about the same time,
> more than 2000 Gt C as CO2---comparable in magnitude to that which
> could occur over the coming centuries---entered the atmosphere and oceans"
> -----------
> The news article you offered, "2 climate studies offer hope on global
> warming" is a good example of misleading pseudo-science reporting.
> For example, the following statement from the article in a discussion
> of feedbacks, gives the reader the impression scientific understanding
> of climate feedbacks is so uncertain that the balance of positive to
> negative feedbacks is still highly debated, as they quote Lindzen,
> whose climate science work has been discredited by extensive peer review:
>
> "For some scientists, including the skeptical Richard Lindzen of the
> Massachusetts Institute of Technology, the jury on feedbacks remains out.
>
> “Climate science is a field that is not highly developed,” he said.
> “Really, it's still in its infancy.”
>
> Other climate scientists would disagree, but as the two new papers
> this week show, researchers are still grappling to understand the
> balance of feedback loops"
>
> While there is a degree of uncertainty, and climate science continues
> to make new discoveries, there is a large consensus among climate
> scientists that the climate feedbacks from human CO2 emissions are
> mostly positive, as the following paper from MIT concludes:
>
> http://globalchange.mit.edu/files/document/MITJPSPGC_Rpt169.pdf
>
> News release from MIT on this scientific paper:
>
> Climate change odds much worse than thought
> New analysis shows warming could be double previous estimate
>
> http://web.mit.edu/newsoffice/2009/roulette-0519.html
> ------------------------------------------
> Vision2020 Post: Ted Moffett
>
> On 10/2/10, *Paul Rumelhart* <godshatter at yahoo.com
> <mailto:godshatter at yahoo.com>> wrote:
>
>
> Understanding feedback in climate science is essential not just
> for laypersons but for climate scientists as well. It's really
> the crux of the whole debate. No feedbacks, or balanced positive
> and negative feedbacks, mean warming of about 1.2C for a doubling
> of CO2 from pre-industrial levels. Not much to worry about, it
> might even be beneficial to humanity. Negative feedbacks reduce
> this value down from 1.2C to even less warming. So the whole meat
> of global warming comes down to positive feedbacks. How strong
> are they? Are they strong enough to overcome the negative
> feedbacks? Etc.
>
> The climate models, whose results have driven the fears of climate
> change, have always assumed positive feedbacks. They just differ
> on how large of a magnitude those values will have. Too large,
> and you get into "tipping point" territory.
>
> Simply identifying all of the possible feedbacks is difficult, let
> alone modeling them. Feedbacks can cause other feedbacks,
> positive or negative, in a cascade of secondary effects. Granted,
> modeling the behavior of what is basically the prototype for
> complex systems is difficult. Which is why I've always wondered
> why they are so sure the end result is catastrophic.
>
> It seems odd to me that more work wasn't done early on regarding
> feedbacks, since they are so critical to the question at hand.
> Lately, there has been some work done on feedbacks, some of which
> aren't modeled by current climate models.
>
> For example, here is a news report about two papers that give some
> more data on two separate feedbacks which aren't currently
> modeled. One would tend to increase the positive feedbacks from
> the models, the other would tend to decrease them:
>
> http://www.chron.com/disp/story.mpl/nation/6841153.html
>
> My gut feeling is that since in the past CO2 levels have been much
> higher than they are now and the system didn't end up with boiling
> oceans or a snowball earth, that the idea of tipping points and
> runaway feedbacks is a fantasy. That doesn't mean that smaller
> positive feedbacks won't be catastrophic, but at least the worries
> about the climate snowballing out of control seem unfounded.
> Maybe in a couple of decades we'll have been able to model things
> much more closely and will be able to pin the numbers down much
> better. Until then, I'd rather we worked on reducing gasoline
> consumption because of pollution and geo-political concerns, and
> ramping up nuclear energy to reduce the need for coal.
>
> Paul
>
> Ted Moffett wrote:
>
> Some people will argue that climate science is too complex and
> specialized for an educated layperson to comprehend, so the
> subject should be left to those with PhD level knowledge. Of
> course, such an argument, when applied broadly, is a major
> blow to the democratic principle that an educated public can
> make informed choices at the ballot box regarding the
> positions politicians assume on domestic economics, education,
> international politics and war, gender, "race" and sexual
> orientation equality, freedom of religion, and so forth; and
> any scientific issue that effects the public: stem cell
> research, genetic engineering of plants, animals or perhaps
> human beings, the safety or not of new IV Gen. fast nuclear
> reactors, the brain development of a human fetus regarding how
> this impacts the ethics of abortion, whether anthropogenic
> climate warming has a high probability of being a significant
> problem in the future, and so forth.
> If a layperson, meaning someone who is well educated but not
> at the PhD level on a given issue, cannot conduct an informed
> broad survey of expert opinion, to arrive at a rational
> objective assessment of the likelihood of there being a
> consensus view, then perhaps society should be managed by
> committees of PHd level experts, not by elected politicians,
> given many politicians and the public at large simply cannot
> comprehend highly technical problems sufficiently enough to
> make rational informed decisions. Perhaps this argument has
> some similarities to the argument of Plato in the "Republic" (
> http://faculty.frostburg.edu/phil/forum/PlatoRep.htm : "This
> rule by society’s best minds is the core concept of Plato’s
> so-called “philosopher kings.” )
> Committees composed of PHds in ethics, law, religion,
> economics, international politics, military strategy,
> education, numerous specialized scientific fields, and so
> forth, would make the important decisions governing society
> for us... Perhaps in some sense this is happening now, given
> the US Congress', and the US public's, manipulation by
> powerful economic and political interests.
> Regardless of the truth of this admittedly thorny question, I
> assume that, given the possible planetary altering magnitude
> of anthropogenic climate warming, for centuries and
> potentially millennia, that will profoundly impact the US, it
> behoves every citizen, every voter, to educate themselves as
> much as possible regarding the climate science involved,
> because the problem boils down to whether the science is
> reliable or not. Anthropogenic climate warming is not similar
> to many other pollution or industrial development problems,
> where we can pollute or impact an ecosystem with future plans
> to realistically recover the ecosystem. Once powerful climate
> feedbacks begin to accelerate impacting global climate (albedo
> reduction from ice loss, ocean warming and carbon sink
> reversal, etc.) the problem is likely to be significantly out
> of humanity's control, unless by extreme and untested
> geo-engineering. There is no compromise or negotiation with
> the physics of Earth's climate system. Regardless of how
> emotionally politicized this issue has become (rather
> irrationally political, it seems), it is fundamentally a
> scientific question, that should be resolved first, if
> possible, before assuming that strong action is indicated to
> address the problem, involving economics, technology,
> lifestyle and the political arena.
> The following scientific presentation on climate feedbacks
> can perhaps be understood by an educated layperson:
> Introduction to feedbacks
> http://www.realclimate.org/index.php/archives/2010/09/introduction-to-feedbacks/#more-4993
> ------------------------------------------
> Vision2020 Post: Ted Moffett
> ------------------------------------------------------------------------
>
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