PPRuNe Forums - View Single Post - Global Warming - split from the A380 thread
Old 5th August 2006 | 13:54
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Dr Dave
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Thanks for the kind words. Taking the above two posts in order:

1. The graphs - yep, they are fascinating and complex. The c.100,000 year cyclicity is caused by cyclicity in the orbit of the Earth around the sun. There are three known such cycles, which alter the distribution of radiation reaching the Earths atmosphere. This cyclicity is responsible for the ice-ages.

However, the pattern is even more complex because you will see that Earth cools slowly, but warms rapidly - i.e. we slowly descend into an ice age, but come out of it quickly. Why should this be? The answer is not fully established but may be linked to carbon dioxide. However a couple of years ago the late, great and sadly missed British scientist Nick Shackleton demonstrated that carbon dixide changes occur before temperature. So, the theory is that changes in orbit leads to changes in biological productivity, and this drives the pattern of change that results. Of course, this scenario is bad news for us...

Incidentally, if you look carefully at the graph in the top right corner you will see an indication of where atmospheric co2 is now...

Regarding the article - yes, it is excellent. There is much that I aghree with there, including the central point that anthropogenic global warming is unproven, and that there is a political band wagon in operation that can be very dangerous indeed. The moves by green groups in the European parliament to apply arbitrary taxation to airline travel is such an example of an ill-judged and misconceived political reaction to the science.

As a young scientist I was told that in order to deal with multiple scenarios all of which fit the available data, one should apply the so-called "Occam's razor", which is that the simplest explanation that fits all the available facts is usually the right one. I suspect that you apply the same logic when, for example, you have a multiple systems failure in the cockpit. For a long time the anthropogenic global warming hypothesis failed the razor - i.e. there were other explanations that appeared to fit better. But, in recent years, as the climate data, the models, the experiments, etc have improved, it now passes the test (with flying colours). The other scenarios require such complexity, and so many assumptions, that they just don't pass muster.

Needless to say that doesn't mean that the theory be proven wrong in the fullness of time, but theres not much evidence of that happening at the moment.