Re: Democratic candidates address the issue of global warming while Republicans snooze...

On Thu, 3 Jan 2008, Islander wrote:

Jean Smith wrote:
In article <0KSdnSrtBYQBU-banZ2dnUVZ_oWdnZ2d@xxxxxxxxxxxxxx>,
Islander <nospam@xxxxxxxxxxx> wrote:

California Poppy wrote:
The issue of global warming may or may not be true. Sadly, the bad
science in Gore's movie makes it difficult to tell. There have been
warm times in earth's history as well as ice ages. But, we dont' know
enough about them to make any certain statements. The idea that human
activity has caused the current global warming (if it is real) has not
been proved. Making all of the changes that it implies could wreck
our economy. So, I favor waiting for scientific proof. Remember that
in the '70's they were saying we were heading into an ice age.

Who was saying that we were heading into an ice age in the '70s?

Go to the website below to follow links to specific references.

http://www.realclimate.org/index.php?p=94

The global cooling myth

Every now and again, the myth that "we shouldn't believe global warming predictions now, because in the 1970's they were predicting an ice age and/or cooling" surfaces. Recently, George Will mentioned it in his column (see Will-full ignorance) and the egregious Crichton manages to say "in the 1970's all the climate scientists believed an ice age was coming" (see Michael Crichton¹s State of Confusion ). You can find it in various other places too [here, mildly here, etc]. But its not an argument used by respectable and knowledgeable skeptics, because it crumbles under analysis. That doesn't stop it repeatedly cropping up in newsgroups though.

I should clarify that I'm talking about predictions in the scientific press. There were some regrettable things published in the popular press (e.g. Newsweek; though National Geographic did better). But we're only responsible for the scientific press. If you want to look at an analysis of various papers that mention the subject, then try http://www.wmconnolley.org.uk/sci/iceage/.

Can you help with the precession theory of orbital forcing? Googling other sources contained claims that said that the northern hemisphere should be building icesheets and others denying it.

I think you may be referring to theories about the change in the axis tilt of the earth which gives us our seasons. Milankovich, a Serbian civil engineer and mathematician, published pioneering work on this in 1930, suggesting that the changes in the polar ice sheets, and possibly ice ages, might be caused by the wobble of the earth as the axis tilt changes over major and minor cycles. The changes are slight, from about 21.5 degrees to about 24.5 degrees and there are a variety of sub variations within this change.

One of these minor variations is called precession and is due to the effects of the gravity of the moon and the sun on a bulge in the Earth's surface at the equator. There are also smaller effects due to Jupiter and Saturn. At present this causes southern hemisphere seasons to be slightly more severe than northern seasons, assuming no other effects are at work.

How much this might affect the climate warming that we are presently seeing is controversial. These cycles are very long, on the order of thousands of years, and the effects are small relative to the major change that we have seen over a relatively short period of time in increasing CO2 levels.

I have a problem with this theory because while winters are colder, the tilt also causes the summers to be warmer. Any long term climate change from this effect must be secondary in scale.
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