Summary

• Warming of the global climate system is unequivocal, with global average temperatures having risen by nearly 0.8ºC since the late 19th century, and rising at about 0.2ºC/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.

• Global sea-level rise has accelerated between mid-19th century and mid-20th century, and is now about 3 mm per year. It is likely* that human activities have contributed between a quarter and a half of the rise in the last half of the 20th century.

• Central England Temperature has risen by about a degree Celsius since the 1970s, with 2006 being the warmest on record. It is likely that there has been a significant influence from human activity on the recent warming.

• Temperatures in Scotland and Northern Ireland have risen by about 0.8ºC since about 1980, but this rise has not been attributed to specific causes.

• Annual mean precipitation over England and Wales has not changed significantly since records began in 1766. Seasonal rainfall is highly variable, but appears to have decreased in summer and increased in winter, although with little change in the latter over the last 50 years.

• 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 NE England and N Scotland show decreases.

• There has been considerable variability in the North Atlantic Oscillation, but with no significant trend over the past few decades.

  Severe windstorms around the UK have become more frequent in the past few decades, though not above that seen in the 1920s.

  Sea-surface temperatures around the UK coast have risen over the past three decades by about 0.7ºC.

• Sea level around the UK rose by about 1 mm/yr in the 20th century, corrected for land movement. The rate for the 1990s and 2000s has been higher than this.

*These findings of IPCC AR4-WG1, discussed in this report, use IPCC terminology to express likelihoods: very likely = >90% probability, likely = >66% probability.

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