Sea levels

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In reply to Carolyn Taylor’s letter (“Cold hard facts”, 25 May), I would like to point out again that a small amount of ice loss is well within natural variability.

Adding 150 cubic km of ice loss to 60 km per year is still an absolutely infinitesimal volume of liquid and would still be less than the figure I quoted of 0.000022 per cent of oceanic volume.

It simply cannot be measured in terms of effect on sea levels. Spreading 150 cubic km over an ocean surface of 361,900,000 square km would not register on any satellite reading.

Carolyn Taylor quotes Grace accuracy in measurements of mean sea level at less than 1 mm. The Jason 2 as used by University of Colorado quotes 0.4mm of accuracy. The interesting thing is that if you read the actual measurement stages and the process of arriving at 0.4mm, the Jason 2 technology sheet enumerates measurement errors of 1cm and less than 3cm for staged processes, and by averaging a few hundred thousand measurements they arrive at 0.4mm.

There is, of course, no way of certifying the validity of this measurement accuracy. It is purely statistically derived. The same will apply to Grace.

Furthermore, a recent paper by Christopher S Watson et all has postulated that mean sea level 1993-2014 has averaged as low as 2.6mm per annum rather than 3.2mm +/- 0.4mm so nothing is set in stone. Sea level gauges are more like 2mm per year.

There is an unavoidable uncertainty in such measurements and applied statistics, and the figures are so small that it could all be due to natural variability anyway.

The climate has changed naturally from the birth of mother Earth and will continue to do so whatever we do.

It is important to bear in mind that even though sea levels rise by somewhere between 2 and 3mm per year they have done so since the last ice age and there is no acceleration involved.

John Peter

Monks Road


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