There are still basic misunderstandings about sea level rise, as exposed by Rob Colmore, once again, and Alastair Bourne with his insults [Weekend Sun, September 13]. For instance, satellite altimetry has revealed that sea level rise across the world's oceans is uneven - contrary to popular belief - due mainly to changes in prevailing weather systems and ocean currents as the planet warms. This is a separate issue from localised tectonic rises and falls which can also cause inconsistent tide gauge records from place to place – equally confusing to some people.

Further variations in sea levels are due to unloading of parts of the earth's crust as the great ice sheets melt, shedding over 500 gigatonnes of ice into the ocean every year. Additionally, as Wesley Parish [Weekend Sun, September 6] points out, recent research indicates the sea floor itself is sinking at varying rates with the extra load as the ocean volume increases.

Sceptics with a poor grasp of science should remember that, by insulting the scientists and politicians with the guts to take a stand against climate change inaction, they have only succeeded in making the issue disappear in their own heads. How infantile is that?

Peter Otway, Omokoroa