Sea level dispute

Had John Peter (Letters, 27 July) taken more than a “cursory look” at the data on Global Mean Sea Level he might have noticed that the information was published by the University of Colorado, not Columbia, as he stated, and only covered the period since 1993.

Had he looked further and consulted the scientific literature on this subject he would have found ample evidence that indeed the rate of sea-level rise is increasing.

For example, a graph (2008) shows that it took about 42 years (from 1900 to 1942) for sea levels to rise 50mm. Subsequent 50mm rises took 28 years (1942 to 1970) and 24 years (1970 to 1994). The current rate, at 3.1mm per year is 50mm in 16 years. That data shows an increasing rate of sea level rise.

The authors, who include John A Church, state: “There has been little net rise over the past several millennia until the 19th century and early 20th century, when… data indicate an increase in the rate of sea-level rise…

“Sea levels are currently rising at the upper limit of the projections of the Third Assessment Report of the Intergovernmental Panel on Climate Change (TAR IPCC), and there is increasing concern of potentially large ice-sheet contributions during the 21st century and beyond, particularly if greenhouse gas emissions continue unabated.”

Similarly, while John Peter might expect the Antarctic sea ice extent to reduce, because of “the warming Antarctic Ocean”, the fact is that it is not, and those who have bothered to take more than a cursory look at the situation find it not at all surprising, since many factors influence the extent of Antarctic sea ice.

Roy Turnbull

Nethy Bridge

Inverness-shire