Solar Variability

 

Composite total solar irradiance - how the brightness of the Sun has changed over the last 35 years

Composite total solar irradiance - how the brightness of the Sun has changed over the last 35 years. Click to enlarge.

While browsing the web for links for my previous post, I came across a page on the web site of the NASA Goddard Institute for Space Studies asking the question ‘How hot was the summer of 2010‘. It’s a dense page and I don’t particularly recommend it, but on it I found the graph above. It shows the intensity of solar radiation reaching the atmosphere above the Earth for the last 35 years. It is an amazing graph. There is the clearly visible 11 year cycle of solar activity that can be seen in sunspot activity, and also some indication that the Sun is currently at a minimum in its output slightly deeper than its previous minima.

I could talk about this graph all night but I really must go to bed. But before I do, let me mention two things

  • Firstly, it has not been constructed easily! You can read about some of the details here – again a difficult page to read. My colleagues at NPL are working with this institute to try to improve their measurements and increase confidence in these results.
  • Secondly, the changes in solar intensity reaching the Earth amount to around 0.25 watts per square metre. Our best estimate for the effect of anthropogenic greenhouse gas emissions is that they are warming the Earth (technically ‘forcing the climate’) by around 2 watts per square metre – 8 times as much.

So as Zebedee used to say, “Time for bed”: Goodnight 🙂

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2 Responses to “Solar Variability”

  1. Looking at the Sun… « Protons for Breakfast Blog Says:

    […] had got off to such a slow start. The Sunspot Cycle is intriguing in itself, but because it weakly affects the amount of solar radiation reaching the Earth, it is also important for calculations about of the possible extent of Global Warming. The story […]

  2. What’s happening to the Sun? « Protons for Breakfast Blog Says:

    […] observations of the Sun from satellites show that the output of light energy from Sun also changes very slightly in synch with the sunspot numbers. Composite total solar irradiance – how the brightness of the Sun has changed over the last 35 […]

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