On Thu, 22 Sep 2005 23:54:32 GMT, clay wrote:

looking at the graph, it appears that there is a similar pattern from
low to high from 1960 to now, as there was about the period from 1910 to
where it peaks (almost the same as now) around 1948. And then it begins
a definite downward trend for the next 25 years or so. So how do they
assume that the trend will continue to climb from this point in time on?

The "observed" has clearly been climbing since about 1900.
The "model" prior to 1950 or so is based on uncertain estimates.
The effects of CO2 & the greenhouse effect are well known,
documented & researched.
Notice the sharp rise after 1950 as the world's population
grew and more people used more fossil fuels releasing more CO2.

Prior to 1950 a lot of coal was freely burned and it's ash &
byproducts may have had something to do with providing a bit of
cooling to somewhat offset the CO2. My guess and just a guess.

BTW, I don't think that this is worst case by a long shot .....
--
Cliff