"Ian Bingham" wrote in message
...
The HadCRUT series of world temperatures show that average world
temperature stopped rising around 2000, and if anything has been slowly
falling since. The question is not so much where the heat energy has gone
(it has evidently gone into beefing up the atmospheric circulation, both
horizontal and vertical) as why temperatures stopped rising when they did.
What happened around 2000 to cause that change?

Ian Bingham,
Inchmarlo, Aberdeenshire.

What happened around 2000 was a very strong El Nino in 1998. This raised
global temperatures to a level only rarely exceeded since. Ignoring the
exceptional 1998 value, temperatures rose from -0.1 in 1975 up to +0.5 in
2005, at a steady rate of 0.2 K per decade. Temperatures have failed to
rise in the following decade ending now. This anomally is know as the
"hiatus" and is currently unexplained. See:
http://www.cru.uea.ac.uk/documents/4...=1363599322327

There was a previous hiatus from 1945 to 1975, which is believed to have
been caused by the aerosols (soot?) from coal fired power stations, ended
when Clean Air Acts were introduced throughout the Western World. It is
claimed that the Asian Brown cloud has not increased the quantity of black
carbon in the atmsophere, but perhaps these hiati are due to SO2 in the
stratosphere from the combustion of sulphourous coals rather than soot in
the troposphere.

Alternatively, if you consider the hiatus as starting around 2005, then the
exceptional summer melt of Arctic sea ice occured then. The summer melts
have remained at around that level since then, so that area of summer sea
ice may have been a tipping point, where the amount of annual melting ice is
enough to keep the ocean surface cooler. (Ths is a bit speculative.)

Plenty of other causes for the hiatus are proposed, some of which have been
expounded here by regulars. The Met Office's answer is:
http://www.metoffice.gov.uk/media/pd...al_warming.PDF

Cheers, Alastair.