Tuesday, March 14, 2006

Time Scales

The Climate Change Debate is being discussed on several discrete fronts. Richard Lindzen (see previous post) stresses the scientific community's inherent weaknesses as well as some of the statistical boundaries that are not being reported properly. I tend to focus on the time element of climate change, probably because I am a trained geologist. I donot understand how some researchers believe that a short-lived research program can produce significant results (until I read Lindzen's section on research funding!). And by short-lived I would include the 1,000 year "hockey stick" approach (which in itself appears to have fallen foul of Lindzen's observations of poor statistical analysis).

So, here are a range of time scales to think about, starting short, ending long:

1 day - the life cycle of a daily newspaper

1 week - the life cycle of a weekly magazine

1 month - the life cycle of a monthly magazine

1 year - the minimum time weather patterns can be compared

25 years - one human generation (could range from ~15 up to ~50)

70 years - life span of a human being (based on three score years and ten)

250 years - the period of time since the Period of Enlightenment began (~1750 AD)

1000 years - the duration of a game of hockey played by scientists who "can't find" their original data

6010 years - the precise duration of the Universe according to fundamentalists and creationists (4004 BC + 2006 AD)

10,000 years - the duration since the "end" of the last glacial period (See Note* below)

100,000 to 200,000 years - existence of homo sapiens (not very precise due to poor fossil record)

65 million years - approximate time that dinosaurs have been absent from the Earth (so much for the movie One Million Years BC!)

600 million years - the period of time that life has flourished on planet Earth

4,000 million years - the period of time some form of life has been present on planet Earth

4,600 million years - the period of time since planet Earth formed around the sun

15,000 million years - the period of time since the Big Bang

* This item is confusing in that the "end" of a glacial period is hard to define. It's a bit like the Grand Old Duke of York when "half way up" was neither "up" nor "down". Global ice ages have a periodicy that is somewhere between 100,000 and 40,000 years from peak to peak. The concept of the end of a glacial period implies a reaction to significant warming, melting of ice and reduction and regression of the ice sheets. Thus is could be said that the present cycle of "global warming" started 10,000 years ago.


Anonymous Jim Masterson said...

I have two comments:

1) 30 years is the minimum time for a trend to be climatically significant. Usually longer time periods are better.

2) The Wilkinson Microwave Anisotropy Probe [WMAP] (easy for you to say, see http://map.gsfc.nasa.gov) places the Big Bang at 13,700 million years ago (give or take 200 million years). This is one data point with a reasonably tight precision. Probably a more "accurate" number would be 15,000 million years--give or take 5,000 million years. It’s amazing how scientific numbers lack error ranges in the popular press. It’s also amazing how most people confuse precision with accuracy.

10:58 AM  
Blogger Paul Ashton said...

Jim, your comment concerning accuracy and precision is so true. When did anyone print the standard deviation around a mean in a newspaper?

11:50 AM  

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