"Graham P Davis" wrote in message
...
John Hall wrote:
In article ,
Alastair McDonald k
writes:

What was it that caused the warming in that decade, or is that a mystery
too?


Lamb doesn't give any possible reasons in "Climate, History and the
Modern World" that I could see. He mentions that there was a general
improvement to some extent from about 1700, peaking in Europe in the
1730s. He also mentions the tendency for big variation from year to year
in the early 18th century.


I've built a graph based on the 1975 GARP analysis of 700,000 years
data. This analysis used cycles of 100,000, 20,000, 2,500, 200, and 100
years. Adding these cycles as best I could - not having the original
data and having to rely on a small graph published 25 years ago - I get
a global maximum temperature occurring towards the end of the 1730s.
Other peaks from 1700 to 2100 are 1855, 1940, and 2050, with the latter
being the highest of the slowly increasing series.

It looks as if you are describing the 90 year cycle, except that 2050
does not fit. During the 17th Century there were less major eruptions
than normal, and that may have allowed the Earth to warm up prior to
1730. One is tempted to suggest that the warming caused the
eruption, by raising surface temperature and via the lapse rate in
the upper crust, increasing the melt in the magma chamber.

If this is correct, then global warming could induce more volcanic
eruptions, for instance at Yellowstone which is now overdue.

Cheers, Alastair.