Recent climate trends
Average global temperature and sea level have risen
since the late 19th century, and at an increased rate over the past
few decades.
- Warming of the global climate system is unequivocal, with
global average temperatures having risen by nearly 0.8 ºC
since the late 19th century, and rising at about 0.2 ºC/decade
over the past 25 years.
- It is very likely that man-made greenhouse gas emissions caused
most of the observed temperature rise since the mid 20th century
(IPCC Fourth Assessment Report, 2007).
- Global sea-level rise has accelerated between mid-19th century
and mid-20th century, and is now about 3mm per year. Human
activities have likely contributed between a quarter and a half of
the rise in the last half of the 20th century (IPCC Fourth
Assessment Report, 2007).
Observed trends for the UK
Average UK temperature has risen since the mid 20th
century, as have average sea level and sea surface temperature
around the UK coast. Over the same time period, trends in
precipitation are harder to identify.
- Central England Temperature has risen by about a degree Celsius
since the 1970s, with 2006 being the warmest on record. All regions
of the UK have experienced an increase in average temperatures
between 1961 and 2006 annually, and for all seasons. Increases in
annual average temperature are typically between 1.0 and 1.7
°C, tending to be largest in the south and east of England and
smallest in Scotland.
- All regions of the UK have experienced an increase over the
past 45 years in the contribution to winter rainfall from heavy
precipitation events; in summer all regions except north east
England and north Scotland show decreases.
- Severe windstorms around the UK have become more frequent in
the past few decades, though not above that seen in the 1920s.
- There has been considerable variability in the North Atlantic
Oscillation, but with no significant trend over the past few
decades.
- Sea-surface temperatures around the UK coast have risen over
the past three decades by about 0.7 ºC.
- Sea level around the UK rose by about 1mm/yr in the 20th
century, corrected for land movement. The rate for the 1990s and
2000s has been higher than this.
- The annual number of days with air frost has reduced in all
regions of the UK between 1961 and 2006. There are now typically
between 20 and 30 fewer days of air frost per year, compared to the
1960s, with the largest reductions in northern England and
Scotland.
- There has been a decrease in the average number of Heating
Degree Days (HDD), and an increase in the average number of Cooling
Degree Days (CDD) in all administrative regions of the UK as a
whole, between 1961 and 2006.
- There has been a slight increase in average annual
precipitation in all regions of the UK between 1961 and 2006,
however this trend is only statistically significant above
background natural variation in Scotland where an increase of
around 20% has been observed. Likewise for an increase in average
winter is only statistically significant in Northern England and
Scotland where increases of 30 to 65% have been experienced.
- Average annual and seasonal relative humidity has decreased in
all regions of the UK, except Northern Ireland, between 1961 and
2006, by up to 5%.
