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Re: [Phys-l] gigo

Let's forget the fringes here--those who would even deny that there has been some warming, that humans have zero effect on the climate, but also those who are call for almost immediate cessation of all carbon emissions, who claim the sky is falling. Long term we know that we will seriously decrease our carbon emissions simply because we are going to run out of coal and oil in the next century or two and unless we tap the ocean methane, natural gas as well (actually relatively soon). Keeping that in mind, then the question becomes HOW MUCH of the current warming is due to human activity especially in light of the fact that we have been in a warming trend since the last ice-age and as pointed out--the curve is not far off that natural warming. To pick up on a sub-thread, is half a degree over a century really above the noise when all natural factors are taken into account. All this leads, I think, to legitimate questions about how much action do we need to take and how soon do we need to do it. While I personally am in the 'better safe than sorry' camp, there are HUGE financial interests at play here--on both sides of the issue.

I note that you average over 20 years to say we're within predictions (but guess that depends on the particular model) but not necessarily over the last 10 years. While we certainly aren't cooling, the 'respite' from increasing temperatures has come at a somewhat inopportune time ,as has a global recession, to spur real, large scale changes. This also couples with rapid development in the East and simply put, a lack of viable alternative to accomplish immediate, massive shifts away from fossil fuels. I'm hoping that the factors you quote below account for only a fraction of the observed warming because its going to take quite some time (I think a century or so) to really and substantially move away from the fossils.


----- Original Message ----- From: "A. John Mallinckrodt" <>
To: "Forum for Physics Educators" <>
Sent: Wednesday, October 13, 2010 1:03 PM
Subject: Re: [Phys-l] gigo

The characteristics of a waterfall depend on minute details of rock sizes, shapes, and placements, wind currents, temperature, etc. but one needn't know more than the general contour from precipice to pool and the flow rate to know 99% of everything most people might care about.

In the case of global warming we know that CO2 concentrations are far larger than they have been at any point in the last million years, we know how much radiative forcing the increased concentrations of CO2 and other greenhouse gases cause, we know the temperature rise to be expected from that increased forcing, and we are seeing temperature rises pretty much in keeping with those expectations. Under the circumstances, it seems to me that those who claim there is no human component to the observed warming have a pretty serious obligation to explain how that could be. To give their clams any credence without demanding that explanation seems to me to indicate a lack of appropriate skepticism.

John Mallinckrodt
Cal Poly Pomona

James Espinoza wrote:

If a model does not take into account the sun, or clouds, or cosmic rays, or
changing orbits,or is incomplete in some other way, and only carbon dioxide
matters, how confident can one be about the predictions?
... When it comes to global warming it appears that many scientists have
lost their skepticism, which I always tell my students is essential in science,
and physics in particular.
Forum for Physics Educators