Are sea level rises real? If so, what problems are caused?

Changing sea levels reshape whole coastlines, often affecting densely populated areas. Scientists want to understand sea level as thoroughly as possible, given the climate change problem, and have gathered increasing amounts of data. G Best’s letter (‘Where is the evidence of rising water levels?’, Open Lines, 17 Feb) says rising sea levels are ‘scares’ and requests the evidence. Maybe he thinks sea level rise does not exist because he has not noticed it with his own eyes? I can assure him that there is plenty of reliable evidence showing it!

DEFRA, the Environment Agency and South West Observatory data has identified which regional coastal sites and features are most at risk from sea level rise within the next 20 years. Sites at high risk according to them include: Westbury Court Garden, Bossington, Lundy Access Road, Godrevy, Penberth, St Michael’s Mount, Mullion Harbour, Cotehele Quay, South Milton Sands, Black Ven/Lyme Regis, Golden Cap, Studland, and Brownsea. Sites at medium risk include: Middlehope & Sandpoint, Brean Down, Woolacombe, Boscastle Harbour, Wembury, Greenway Quay, Burton Bradstock.

South West sea levels are set to rise between 20-80cm by the 2080s, depending on whether and by how much we all cut or increase emissions. Newlyn in Cornwall has one of the longest sea level records in the UK and sea level here was 161mm higher in 2006 than when records began in 1916 on average. Average wave height increased, from 1.8m in 1962 to 2.3m today (Seven Stones Light-vessel). Such changes may adversely affect sea defences, harbours, homes, businesses, infrastructure, maritime heritage as well as natural assets and biodiversity according to the Proudman Oceanographic Laboratory.

The National Trust has published research into the long-term future of the coastline and the impact that climate change (through sea level rise, coastal flooding and increased erosion) was predicted to have on this coast over the next century. In the south west 279 kilometres of National Trust coastline are at risk from erosion, with 852 hectares of Trust coastal sites becoming at risk of tidal flooding.

Information on global sea level rise, published by NASA in June 2006 showed sea level rose, on average, 3 millimetres per year between 1993 and 2005. Half of this was attributed to melting ice and the other half to thermal expansion as the ocean absorbs excess energy. Due to climate change scientists at NASA and elsewhere are particularly concerned about: thermal expansion—the tendency of warm water to take up more space than cooler water; the addition of water to the sea from melting glaciers; and changes in salinity, given that fresh water is less dense than salt water and therefore takes up slightly more space than an equal mass of salt water.