Now I don't want to get involved in the global warming debate, but having an obvious interest in trying to predict snowfall some understanding of how the earths' temperature fluctuates would be useful. Which means you come across both sides of the argument quite frequently. The current sticking point seems to be is how much influence the sun plays in the warming of the earth. One side says very little compared to manmade influence the other says it has total influence and man is but negligible in the equation. Now as said I don't want to get involved but one thing that both sides agree on is that the energy being received from the sun has been waning as it passes through the low point of its 11 year cycle. However there is a lot of argument that this downward trend in solar activity is going to be more distinctive and last far longer.
The question is, what does that mean to us who look forward to cold times?
Dr Scaife from the UK met office says that the UV output from the sun (which varied greatly with overall solar activity) does have an effect on over all winter temperatures, but not in a direct way. The UV is absorbed by and thus affects the temperature of the Stratosphere. When there is less UV the Stratosphere is cooler, the effects of which percolate down through the atmosphere, changing wind speeds, including the jet stream that circles the northern hemisphere. This change or kink in the Jet stream blocks warm westerly winds reaching Europe whilst allowing in cold winds from Arctic Siberia. The key point in his argument is that although this causes Europe and North America to be colder, other areas are warmer as it is only a change in the circulation of the air not a dramatic change in over all climate.
One of the problems is that data on the UV output from the sun is hard to measure from the earths' surface and accurate readings have only been taken since the launch of the source satellite in 2003. Observations and analysis of the first few years of output from source seemed to raise more questions than answers concerning a trade off between UV radiation absorbed and energy at visible wavelengths that reach the earth. Mike Lockwood from Reading University thinks these readings could be particular to this phase of solar activity, marking the end of a phase of high output and a transition into a less active phase.
Professor Lockwood also says that although short term changes in solar output may not affect the global big picture, they can have a powerful impact on local weather patterns, particularly over Europe and Eurasia, as was suggested by Dr Scaife.
Since 1990 research by the National Solar Observatory in Arizona has been monitoring the decline in sunspot activity. Sunspots are the Harbingers of the magnetic activity on the sun that lead to the ejection of particles towards the earth, via flare events and coronal mass ejections. Their research finds that the magnetic field strength of sunspots has been declining, and if it drops too low, a level that could be reached by 2016 if the current trend continues, then there will not be enough for sunspots to form at all. A situation that has been seen before, between 1645 and 1715, a time otherwise known as the Maunder Minimum.
Well no matter what you believe mans effect on the earths' temperature is. It is looking likely that we have some cold winters ahead.