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Re: [LUG] OT: Snow was Why don't they learn

 

On Thu, 2010-01-07 at 18:06 +0000, Simon Waters wrote:
> Philip Whateley wrote:
> > 
> > What I found interesting was the recent British Antarctic Survey Ice
> > Dome C data for the last 800000 years.
> > 
> > It shows that every inter-glaciation temperature spike for the past 500k
> > years has gone to around 5degC above present. 
> > 
> > It would be interesting to know whether the predicted anthropogenic
> > 2-3degC rise is in addition to the 5degC we can expect as a result of
> > solar activity, or whether the 2-3deg is the net effect of solar
> > activity, greenhouse gas emissions and particulate emissions reducing
> > solar absorption.
> 
> The temperature rise forecast is CO2 forced, so it is a warming that is
> expected over recent historical averages including any expected changes
> in climate due to additional CO2 (and methane), but I don't think there
> are any substantive changes in natural climate expected over the time
> scales of interest (i.e. next 100 years).
> 
> The larger historical fluctuations as I understand it are on a much
> longer time scale (100,000 year cycle).
> 
> I don't think the fluctuations you mention are due to solar activity but
> due to variations in the earth's orbit (Milankovitch cycles).
> 
> The peak of the current interglacial was 21,000 years ago as I
> understand it. Where did you get the idea it would get 5 degrees warmer
> naturally, or are you meaning in 75,000 years when the cycle would repeats?
> 
> http://stratus.astr.ucl.ac.be/textbook/chapter5_node13.html
> 
The data from the ice core samples (available for download from
http://news.bbc.co.uk/1/hi/in_depth/sci_tech/2009/copenhagen/8393855.stm)
shows an interglaciation spike beginning about 19,000 years bp. The data
is based on deviation from the average for 1900-2000, as zero. The data
shows the the current (baseline) temperature some 3 to 5 degrees cooler
than the last 4 interglaciation spikes.

The data also shows some other interesting anomolies, such as CO2 peak
lags temperature peak by around 30,000 to 40,000 years?

Phil




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