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SUMMARY:Causes of Climate Change and the Role of the Sun - Professor Joann
 a Haigh
DTSTART:20160224T210000Z
DTEND:20160224T220000Z
UID:TALK63754@talks.cam.ac.uk
CONTACT:Jamie Fox
DESCRIPTION:Do changes in the Sun affect the Earth’s climate? Variations
  in the Earth’s orbit clearly have a major effect\, controlling diurnal 
 and seasonal cycles as well as the onset of ice ages\, but what about the 
 impact of intrinsic variability within the Sun? Observations of sunspots d
 ate back to at least the 2nd century BC\, and so have speculations that su
 nspot numbers are related to weather\, although many such claims were stat
 istically dubious. Nowadays\, the need to distinguish natural from anthrop
 ogenic causes of changes in climate has placed new emphasis on quantifying
  and understanding any such relationship. Another consideration in the pas
 t was the lack of evidence of any measureable variation in the Sun’s ene
 rgy output. The advent of satellite measurements of solar irradiance\, how
 ever\, together with the collation of well-calibrated records of atmospher
 ic and oceanographic parameters\, have enabled considerable progress to be
  made in establishing evidence of solar-climate links on a range of timesc
 ales. Our research shows that when the Sun is more active the atmosphere r
 esponds by a warming of the stratosphere in low latitudes but that the pre
 dominant signal in the lower atmosphere appears in mid-latitudes. Associat
 ed with this the jet streams weaken and move polewards\, along with the mi
 d-latitude storm-tracks. We have found that an important factor driving th
 is response is the absorption of solar UV radiation in the stratosphere an
 d we have been able to identify a mechanism for dynamical coupling between
  the stratosphere and the atmosphere below.Over the past few years some sa
 tellite measurements have suggested that variations at UV wavelengths are 
 larger than previously understood. I will discuss the implications of thes
 e spectral variations for the stratosphere and describe how measurements o
 f stratospheric ozone might be used synergistically with those of solar sp
 ectral irradiance to improve knowledge of the variations in both.
LOCATION:Nihon Room\, Pembroke College
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