Weakest solar cycle in 100yrs could intensify drought
News from NASA this week that on-going weak solar activity will continue, leading to the weakest solar cycle in around 100 years, could have important implications for the UK's weather.
Research over the last few years has pointed to a link between low solar activity, and incidences of 'blocking' weather patterns.
In three out of the last four winters, the jet stream has been much weaker than normal, leaving us more exposed to colder air from the north and the east, as 'blocking' areas of high pressure become established.
In these situations, winters are not just colder than average but drier, too.
It's these weather patterns that have led the government to warn of the risk of stand-pipes in the streets next summer should winter again be dry in southern and eastern areas.
It suggests the government could be right to be worried about the risk of low winter rainfall in coming years, and the implications for water supplies in parts of the UK.
Normally our winters are dominated by a strong jet stream, bringing mild air and rain in from the west.
Winter rainfall is crucial in that evaporation is very low, and plants and trees don't take up much of the water in the ground, and this is the time when ground water levels and reservoirs normally recover.
In summer, evaporation and water taken up by plants and trees in all but the very wettest summers outweighs any rain that falls.
The theory that weak solar activity could impact our weather gained credibility when Professor Mike Lockwood of Reading University published research two years ago.
He found a correlation between weak solar activity and the occurrences of 'blocking' weather patterns, leading on average to colder & drier winters.
Professor Mike Lockwood said that weak solar activity does not guarantee colder winters, but suggests that such winters could become more frequent.
There could also be implications for weather at other times of the year.
The intense heat wave that Russia and parts of Eastern Europe experienced in summer 2010 was also caused by a similar blocking high.
Professor Lockwood told the New Scientist following this event 'there's enough evidence to suspect that jet stream behaviour is being modulated by the sun.'
And it's certainly a headache for computer models that predict our future climate based on increasing levels of man-made greenhouse gases.
They are unable to model the impact of weak solar activity, simply because the precise mechanism of how this affects climate patterns is unknown.
These climate projections suggesting that winters will become milder and wetter, with summers drier and warmer, have been of little use to the water authorities in the south and east of the UK who are trying to cope with successive dry winters.
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