Re: population growth & physics ed

[David Dockstader <DRDOCK00@UKCC.UKY.EDU>]

On Sat, 13 Jul 1996 17:25:26 -0700 Leigh Palmer said:
> ....and also misleading. Tell me about this 130 years of record-keeping. You
> sound as if you believe measuring Earth's temperature has been done in the
> same manner for 130 years, and that there is an unbroken record covering the
> period of measurements done by that method.
When people want to get around this problem they look at the geologic record.
The usual considerations are:  1. Carbon dioxide and Oxygen-16/18 ratios in
ice cores from glaciers.  We now have cores from Greenland (all the way to the
bottom of the ice, and Antarctica which provide a record for over 200,000 years
2. Sea level.  When it's warmer the ice melts and sea level rises.  The level
of sea level is recorded in beach terraces.  3. O-16/18 ratios in foraminifera
recovered from sea floor sediments.

>                   ... The best work that has been done has detected a rise
> in temperature over this century of about one half degree Celsius (with
> large uncertainty). Whether this rise is large or not is seldom mentioned,
> but it is not a large rise even by historical standards. It is thought that
> a larger excursion occurred in this millenium (I forget the year) which was
> so striking it produced what is called "the year without a summer"...
> Leigh

During the year without summer the temperature supposedly dropped
around 2 degrees Celsius.           This was the direct result of the eruption
of Krakatoa in Indonesia in 1883 and can not be compared to a long term global
trend in terms of significance.   Changes of as little as 4-5 deg C mark the
difference between ice ages and interglacials.  In terms of melting of glaciers
changes in weather patterns, rain fall, and crop production I think most of us
would see a half a degree as significant.

The correlation between Carbon dioxide levels and temperature are pretty well
established.  The exact mechanisms are less well understood since the carbon
cycle is pretty complex.  What are really speculative are the economic issues.
What people want to know is how many dollars will it cost if we ignore the
problem and how much will it cost to solve the problem and at what level of
solution does the ratio  become 1:1.

What should we teach in a Physics class?  We can certainly teach how the
greenhouse effect works and the role of various atmospheric gasses in
controlling our climate.  We can also expose students to data showing
carbon dioxide and possibly ave temp rising.  Should we mention projections
when we don't know how they were made?  Should we discuss economic issues?
How do we leave students with the understanding that science can contribute
to our understanding of environmental problems, but usually can not give us
nice neat solutions?