Refreshments from 7pm
The need to distinguish natural from anthropogenic causes of climate change places significant emphasis on quantifying and understanding any impact of the Sun. I will outline what is known about variations in solar output and review the evidence for solar influences on climate. The global average temperature response is modest, but detectable, on century timescales. There is, however, increasingly robust evidence for somewhat larger solar signals on regional climate, particularly in mid-latitudes with influence on the positions of the jet streams and storm-tracks.
An important factor driving this response appears to be the absorption in the stratosphere of solar ultraviolet radiation, followed by a dynamical coupling which transfers a solar signal to the atmosphere and surface below. Over the past few years the Sun has been in a state of low activity and some satellite measurements have suggested that the solar spectrum has been behaving in a strange and unexpected way. The talk will finish with a discussion of recent work on the implications of these spectral variations.