The near coincidence of the perihelion (the EarthÂs closest approach to the Sun) and the winter solstice reminds me of some recent conversations with one of my conservative relatives who listens to talk radio. We disagree on whether global warming is human caused or whether it is simply the result of natural climate cycles. To be clear, I am no global warming apologist. The human planetary chemical experiment of increasing CO2 levels 30% over a century and a half is the most likely cause IMHO, and the appropriate precautionary principle response would be a massive and expensive conversion to renewable energy and sustainable technology. But, some would say that global warming is caused by changes in the Earth's relationship to the Sun, invoking a form of the Milankovitch cycle. Thus, there is nothing that requires a response, since the change is Âall natural. << http://en.wikipedia.org/wiki/Milankovitch_cycles >> This was brought home to me today (and tomorrow) by the relative closeness of the Sun's perihelion to the winter solstice. In another book I am currently reading, the author states that the Sun's solar longitude moves by 1.7463 degrees every 100 years. So, about 5,200 years ago, perihelion would have coincided with spring (about 90 degs of solar longitude away from its current solar longitude), and about 10,000 years ago, at the end of the last ice age, perihelion would have coincided with summer solstice. The solar aphelion (the EarthÂs farthest passage from the Sun) would have coincided with the winter solstice. Again, although I believe in human chemical-based cause for global warming, the current position of the solar perihelion would seem to support the idea that global warming is a consequence, at least in part, of natural climate cycles. - Canopus56(Kurt) __________________________________________ Yahoo! DSL  Something to write home about. Just $16.99/mo. or less. dsl.yahoo.com