GLOBAL warming is likely to increase disruption to lifeline ferry services around the west coast of Scotland, at a cost of tens of millions a year, according to new research.
Scottish scientists used satellites to monitor wave heights around the Western Isles and predict how they might be affected by climate change.
Their results, due to presented at a conference in Vancouver next month, suggest that small increases in wave height could cause a large rise in cancellations.
They conclude bigger, more expensive boats may be needed to protect timetables, increasing pressure on subsides.
The research is part of a UK-wide project co-ordinated by the Tyndall Centre for Climate Change Research.
Although the west of Scotland is believed to be protected from rising sea levels, fishing, tourism and aquaculture could all be affected by climate change.
Scientists at the University of Highlands and Islands and Southampton Oceanography Centre analysed nine years of data to assess wave heights in the Sea of the Hebrides. Ferries from Oban to Barra and South Uist pass through these waters, while services to Coll and Tiree are exposed to similar conditions. Already about one in 20 services can be cancelled, diverted or delayed by more than an hour in a bad year.
The study found wave heights above four yards tended to be associated with disruption. A model was then used to measure the impact of changes to the North Atlantic Oscillation (NAO), a natural and recurring pressure pattern.
John Coll (Environmental Research Institute, Thurso) one of the authors, said: “Most of the global climate models simulate an increase in the NAO index. When the NAO is more positive we tend to get more Atlantic cyclones and westerly storms coming our way.
”With those come coastal impacts, Such as disruption to ferries and flights.”
In other words, their model suggested that small increases in the NAO could push significant wave heights above the critical four-yard mark far more frequently.
They estimate that disruption to services already costs £10m a year.

for further information:
John.Coll@thurso.uhi.ac.uk