Re: When London is submerged and New York is awash...
From: Jonathan Kirwan (jkirwan_at_easystreet.com)
Date: 01/14/05
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Date: Fri, 14 Jan 2005 11:22:53 GMT
On Thu, 13 Jan 2005 16:19:51 -0800, John Larkin
<jjlarkin@highSNIPlandTHIStechPLEASEnology.com> wrote:
>If you were to take some nice measurable parameter, say mean world
>temperature or percent surface glaciation or sea level or something
>like that, and graph it over the last million years maybe, the
>variations would be stunning. I'd think that covering half of North
>America with glaciers for a few millenia qualifies as "climate" as
>opposed to "weather." We even had a mini-ice-age around 1700.
>
>Thinking of such a measurable parameter as a signal, there's no
>distinction between weather and climate but the observer's time scale.
>The overall signal is noisy and chaotic, perhaps fractal on time,
>perhaps having numerous periodicities.
>
>It's obvious that the predictability of weather drops radically with
>the prediction time, hitting zero in something like a week or so. You
>conjecture that predictability somehow returns at longer time scales.
>That sort if thing is certainly possible, but it assumes a signal that
>has high-frequency noise but predictable slow behavior; I don't think
>the geological record indicates anything like that. I also don't trust
>dynamic simulations of chaotic systems that are untested and
>untestable and politically divisive.
All I can suggest to you, John, is that you read the TAR with some thoroughness.
The section from Working Group I, in particular. I can't spoon feed you; the
earth is pretty complex. But over time, scientists have gotten a much better
handle on some of that complexity. You really need to get some respect for the
concept of climate, separate from weather. And I can't ram that into you. You
will have to burnish it in yourself, just as you have what you know about
electronics. It takes time and effort, no escaping it.
What is present now *is* worthy of your respect. But you will only see that
when you take some time to see. Let me point out a single detailed thread, in
order to make my point above.
In 1971, a peer-reviewed research paper (short, but to the point, by Rasool and
Schneider) pointed out that it appeared that the greenhouse effect of CO2 was
saturated and that dumping more CO2 into the atmosphere wouldn't make any
difference, at all. It also covered some ideas on aerosols, as well, and these
indicated a cooling effect. The news reports of this paper started talking
about "global cooling" instead of "global warming."
Was the science good? Yes, as far as it went. In fact, the thrust on aerosols
is still useful. But the fact was that the R&S paper didn't predict the future
climate of the Earth. It did attempt to predict the climate sensitivity to CO2
and to aerosol forcings. The predicted CO2 sensitivity in R&S is today regarded
as 'rather low' and a footnote in R&S admits this and points out that even at
the same time other authors (Manabe and Wetherald) found sensitivities three
times as large.
A second footnote [footnote 14] in R&S, though, was really far more serious and
it gets to the nub of today's view of R&S. The footnote points out that the
sort of model used is only a 1D radiative model and is only suitable for
examining the effects of __small__ perturbations about current climate values.
Now, as an engineer, I'm sure you understand the difference between small signal
simulations for AC, for example, versus large signal analysis which cannot
ignore the non-linearities. The authors (R&S) were well aware of the
limitations of what they'd done and new that it was merely a 1st step, so to
speak.
What accounts for the differences with Manabe and Wetherald for example are
different CO2 abs coeffs, different lapse rate specs, and different CO2/H20
overlaps, to name a few. And the R&S model used is a 1D model that lacked
significant feedbacks (for one example, the albedo of ice.) It's a highly
simplified model.
Of course, the newspapers didn't understand any of this. They just saw the
"cooling" and reported that as the news of the day.
Meanwhile, criticism of R&S appeared in Science by three other climate
scientists and R&S not only agreed with much of it, but in their letter as a
response included a new very serious problem no one else had highlighted.
The concluding section contains some guesses towards future aerosol levels.
Quoting: "Even if we assume that the rate of scavenging and of other removal
processes for atmospheric dust [conflated with 'aerosol' in the article, I
believe -- JK] particles remains constant, it is still difficult to predict the
rate at which global background opacity of the atmosphere will increase with
increasing particulate injection by human activities. However, it is projected
that man's potential to pollute will increase 6 to 8-fold in the next 50 years.
If this increased rate of injection... should raise the present background
opacity by a factor of 4, our calculations suggest a decrease in global
temperature by as much as 3.5 C. Such a large decrease in the average
temperature of Earth, sustained over a period of few years, is believed to be
sufficient to trigger an ice age. However, by that time, nuclear power may have
largely replaced fossil fuels as a means of energy production."
It's clear now, a third of a century later, that the R&S estimates of the
effects of CO2 were wrong. However, they *were* right on the central point that
the current levels of CO2 are indeed largely saturated in the main 15 micron
region. However, what they didn't know at the time was that the edges of that
band __are not__ saturated. In fact, a substantial effect remains from that
portion.
The R&S paper was simply mistaken about the net effect of CO2. Subsequent
work using so-called line-by-line calculations, using the latest emission
spectra from HITRAN and with realistic atmospheric conditions of pressure,
temperature, water vapor, etc., and detailed analysis of the depth that each of
these wavelengths reach in the earth's atmosphere go FAR BEYOND where R&S could
have hoped to have done, back in 1971. And today, these results clearly show
that there is a substantial, remaining forcing effect from additional CO2
releases in our atmosphere.
In other words, John, it takes a much deeper study to fully apprehend how it is
that the calculations are arrived at for the CO2 forcings alone. The details of
this aren't trivial. And this is just one part of the broader picture. But the
fact that the complexity today includes 3D spatial gridding, as well as time,
and carefully propagates wavelengths to compute which layers of the atmosphere
receive which energies from space ... none of this means it is wrong or poorly
done. It isn't. Each step of the way, many scientists carefully examine the
assumptions and the modeling and the choice of parameters that mediate between
different modeling scales of space and time, for example. And problems are
routinely reported, new areas suggested for further research, etc.
But enough time has now transpired that the central result is known. There is
still much more to do, wide uncertainties that need to be narrowed, more
assumptions to be vetted through new experimental testing, etc. But the central
result is know. The anthropogenic impact on the net forcings over
pre-industrial times is substantial and very likely more than 50% of that total
over the last 50 years, even including the cooling of human released aerosols
(which has a substantial, opposing effect.)
>So, tell me, what caused the mini ice age? What caused the *big* ice
>ages? What would be the natural trend NOW without human effects? Is
>the conjectured human-caused warming aiding or bucking the natural
>trend?
You can actually find information on the estimates in the TAR that I already
mentioned and in some of the reports I've cited. Particularly in:
"Historical evolution of radiative forcing of climate"
http://folk.uio.no/gunnarmy/paper/myhre_atm_env01.pdf
Go look.
In addition, even that report is years old (2001). I also cited another report
that is 2004 and deals with new, better understandings of solar forcings.
Frankly, I get tired of repeating myself about looking at the reports, though.
There is so much excellent science done on the subject now and there is no real
excuse for not spending some time with it, if interested or if you plan to
express an opinion that you wish to be taken as an informed one.
On solar forcings, there is a new site here that includes a detailed overview
going back billions of years at:
http://www.nap.edu/books/0309095069/html/
You might also try that site. I mentioned it before, but then I'm never sure if
anyone ever bothers to read.
I cannot force-feed knowledge. No one can. It must be earned. Go read.
Learn. The information is there for the taking, readily available, well
prepared, and excellent.
Jon
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