What is already happening
Air
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
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.
