Global Warming?

[Brad De Long]

>Dear Doug and the Left Business Observers,
>
>A few "old timers" have asked me an interesting question.
>
>Vice-President Al Gore has stated that the earths temperature hasn't
>been this warm in 400 years.  The "old timers" want to know what caused
>the earth to be this warm 400 years ago?  After all there was little or
>no use of fossil fuels used back then.  No internal combustion engines.
>No airplanes.  Hmm.  Space rockets?
>
>Sincerely,
>Tom

Climatologists don't know.

One suspicion is that the sun was a little bit brighter. Another suspicion
is some subtle and poorly-understood interaction of the axis of the earth's
spin with the eccentricity of the earth's orbit.

But before the 1400-1800 period, things were definitely a bit warmer than
they are right now...

Brad DeLong

Professor J. Bradford De Long
Department of Economics, #3880
University of California at Berkeley
Berkeley, CA 94720-3880
(510) 643-4027; (510) 283-2709 voice
(925) 642-6615; (925) 283-3897 fax