"Brendan DJ Murphy"
wrote in message
...
Can somebody please explain exactly what is
being shown he

http://tinyurl.com/rekh

I assume it shows the difference between the
"current" sea surface temperatures and "normal"
sea
surface temperatures.

My questions is, how do they define "normal" ?

I noticed just yesterday that the Baltic Sea was
a VERY dark blue colour (about -2 deg C from
normality on the scale)
Today, the same area is predominantly a cyan
colour ( ie: 0 deg C away from normal.)

Does this imply that the Baltic Sea has actually
risen in temperature?
Or perhaps it has just remained the same
temperature at a time when it normally should drop
in
temperature.

Is "normailty" defined as the average
temperature for the same date over x number of
years? If so,
what is the value of x ?

There is/are no absolute value(s) of x. If skies
have been clear SST _estimates_ may be quite
accurate (satellite). If not, the error bars are
large (dependent on a few ships, buoys at best).
This is the situation for the daily estimate of
SST.

For the climate/mean values of SST the situation
is a little better, but not much. Therefore, the
SSTA may be larger or smaller than estimated.
Worst case - actual SST is over estimated and
climate SST is underestimated or visa versa.
Persistence, may be the best way to gauge real
anomalies, check daily.