keith_nuttle wrote:

If you read the original article you would see that the difference in pH
they are talking about is in the neighborhood of 0.03 pH units. This is
insignificant and does not indicative anything except the precision of
the pH measurement and the sampling. Since the difference is the
precision of the measurements there is nothing to do with global warming.

In a controlled laboratory environement you can measure with .001
precision. But that's not easy.

pH is a theoretical amount of Hydrogen molecules in the solutions. In
practice pH is a measure of the impurities in water, and is
significantly affected by the temperature of the solution. It is also
affected by the actual materials in the solutions as the the amount of
Hydrogen ions are affected by the interactions of the compounds in the
solutions.

You are mixing several things together. pH is a negative logarithm of
H+ ions activity in water. Period. Presence of other substances may
change this activity, but you are not measuring these substances, you
are measuring pH.

pH is measured using the electrical properties of the solution. Because
of the quality of the electronics the precision of the measurements are
several powers more accurate than the precision of the chemical
properties that are being measured.

No idea what you mean by "precision of chemical properties". No such
animal AFAIK.

The electronics are standardized against two reference solutions. The
accuracy of these solutions is about +/- 0.01 based on the suppliers of
the standards. See a typical specification sheet for one of those
standards is at

http://www.coleparmer.com/catalog/pr...sp?sku=0594242

http://www.ph-meter.info/pH-electrod...ration-buffers

Calibration buffers have pH measured with +/- 0.001 accuracy, and
that's the real limit of pH measurements. Hard to reach, but it can be
done.

In practice the precision of laboratory measurements of pH is about +/-
0.03 one one sample. When you take dozens of samples there is
additional error. So you can see the differences they are trying to get
funding to study is nothing but the precision of the measurement of the
pH. (If you google you can find many papers on the laboratory precision
of pH measurements.)

See above. Attainable limit is 30 times lower than you suggest. 0.03 is
a good accuracy in the standard lab environement.

Now, if someone can explain to me how they can say there is a 0.4 degree
change in the mean temperature of the earth when the daily temperature
difference across the surface of the earth is about 100 degrees. I don't
know much about temperature reading and statistics.

Simplest approach will be to average all measurement done by all
meterological services in the whole world during whole year. As they
stick to precise termometers and to precise procedures, data are
comparable on a year to year basis (or - more general - any period to
period basis). And I suppose the real thing is done in similar way,
probably with weighted averaging to account for non-uniform
distribution of measuring points.

Borek
--
http://www.chembuddy.com
http://www.ph-meter.info