What is already happening
Marine air temperature measurements made by Voluntary Observing ShipsThe World Meteorological Organisation's Voluntary Observing Ships programme is a scheme recruiting ocean-going vessels to collect and report meteorological observations. At present there are approximately 4000 ships involved in the programme. have been used in a new dataset of daily air temperatures and other marine meteorological variables currently under development at the National Oceanography Centre, Southampton. This dataset shows that the air temperature over the seas near the UK (7W:3E and 50N:60N) has risen over the period 1970 to 2006 at a similar rate to the The Central England Temperature is a time series of average monthly temperatures representative of an approximately triangular region of the United Kingdom enclosed by Bristol, Lancashire and London. Beginning in 1659, it is the world's longest continuous time series of observed temperatures.Central England Temperature (CET, Parker et al. 1992). However, there are strong regional variations in the linear warming trend over UK territorial waters. Marine air temperatures have risen faster than the CET in the Eastern English Channel and across the majority of the North Sea. The Scottish Continental Shelf, North-West Approaches and Northern North Sea have seen a slower rise than CET and the Irish Sea, South-West Approaches and the Western Channel have seen marine air temperature increasing at a comparable rate to CET. Marine air temperature spatial gradients are thus increasing in the Northern North Sea. As for sea surface temperature (Holliday et al. 2007), air temperature in the winter of 2005/6 was colder than recent years, but the second part of 2006 saw some of the warmest average monthly temperatures in the record.
Due to a decline in the number of reports from Voluntary Observing Ships our confidence in the estimates of marine air temperature has decreased over the last decade, both in UK waters and globally.
Sea surface temperature linear trends within UK Coastal Waters are broadly similar to marine air temperature in both magnitude and spatial pattern.
Sea surface temperatures (SST) in the north east Atlantic and UK coastal waters have been rising since the 1980s, most rapidly in the southern North Sea and the English Channel. Despite a relatively cold winter in UK waters in 2005/2006 anomalously rapid warming in the spring and early summer meant that 2006 became the second warmest year in UK coastal waters since 1870.
The temperature of the upper ocean (0-800m) to the west and north of the UK has been generally increasing since the 1970s. A significant period of warming occurred from 1995 to 2003. The decadal-scale pattern of temperature around the UK reflects the mean conditions of the North Atlantic which has evolved from a maximum in the early 1960s and a minimum in the 1980s and 1990s.
West of the UK the water of the deep oceanThe part of the ocean that does not cover the continental shelf margins (the shallower water adjacent to land masses). (>1000m) comes from the Labrador SeaA region of the North Atlantic Ocean located between southwest Greenland and northeast Canada. It is one of two main locations where cold, dense surface water sinks to produce south-flowing North Atlantic Deep Water, the other location being the Greenland Sea. and has cooled since 1975. North of the UK, the deep water (800 m) flows from the Nordic Seas and shows no long-term trend since 1950.
In the northern North Sea the temperature is most strongly influenced by inflowing North Atlantic water, showing similar decadal variations and a general warming since the mid 1980s. In the southern North Sea, atmospheric forcing is the dominant influence, with ocean temperatures being generally cool from 1970 to 1987 when a "switch" to warm conditions occurred.
The upper 1500 m of the North Atlantic has warmed since 1999 and remains anomalously warm up to the end of 2006, especially in the zone between 50-70°N.
What could happen
The UK Climate Impacts Programme (UKCIP02, Hulme et al., 2002) shows potential sea surface temperature (SST) rises around the UK coast under different scenarios of greenhouse gas emissions, with more pronounced warming in the southeast than the northwest. The range of future increase in SST in the southern North Sea is 1.5 - 4 ºC by the 2080s whilst that at Rockall is only 0.5 - 2 ºC. New scenarios for the UK are currently being developed UKCIP and are due to be launched in autumn 2008.