A brief look at the Sun’s influence on Earth’s climate

NASA produces much of the clearest writing I have seen about modern science.  Much of this gets far too little attention, IMO.  For anyone interested in understanding the dynamics of Earth’s climate, esp cutting edge climate science, their websites are a good place to start.

From the website of NASA’s Jet Propulsion Laboratory

The Active Cavity Radiometer Irradiance Monitor Satellite (ACRIMSAT) Mission will measure Total Solar Irradiance (TSI) during its five-year mission life. The ACRIMSAT spacecraft, carrying the ACRIM III instrument, will be secondary payload on a Taurus vehicle scheduled to launch in December 1999. The instrument, third in a series of long-term solar-monitoring tools built for NASA by the Jet Propulsion Laboratory, will continue to extend the database first created by ACRIM I, which was launched in 1980 on the Solar Maximum Mission (SMM) spacecraft. ACRIM II followed on the Upper Atmosphere Research Satellite (UARS) in 1991. … The Active Cavity Radiometer Irradiance Monitor (ACRIM) I instrument was the first to clearly demonstrate that the total radiant energy from the sun was not a constant.  See the NASA fact sheet for more information.  (source)

From the website of the Active Cavity Radiometer Irradiance Monitor Satellite project

The Earth’s weather and climate regime are determined by the total solar irradiance (TSI) and its interactions with the Earth’s atmosphere, oceans and landmasses.

Evidence from both 29 years of direct satellite monitoring and historical proxy data leaves no doubt that solar luminosity in general, and TSI in particular, are intrinsically variable phenomena.

• Subtle variations of TSI resulting from periodic changes in the Earth’s orbit (Milankovich cycles: ~20, 40 and 100 Kyrs) cause climate change ranging from major ice ages to the present inter-glacial, clearly demonstrating the dominance of TSI in climate change on long timescales.
• TSI monitoring, cosmogenic isotope analyses and correlative climate data indicate that variations of the TSI have been a significant climate forcing during the current inter-glacial period (the last ~ 10 Kyrs.).
• Phenomenological analyses of TSI monitoring results during the past (nearly) three decades, TSI proxies during the past 400 years and the records of surface temperature show that TSI variation has been the dominant forcing for climate change during the industrial era.
• The periodic character of the TSI record indicates that solar forcing of climate change will likely be the dominant variable contributor to climate change in the future. 

Monitoring TSI variability is clearly an important component of climate change research, particularly in the context of understanding the relative forcings of natural and anthropogenic processes. The requirements for a long-term, climate TSI database can be inferred from a recent National Research Council study which concluded that gradual variations in solar luminosity of as little as 0.25 % was the likely forcing for the ‘little ice age’ that persisted in varying degree from the late 14th to the mid 19th centuries. A centuries-long TSI database will have to be calibrated by either precision or accuracy to a small fraction of this value to be of any use in assessing the magnitude of solar forcing.   (source)

For more information

(A)  “Monitoring the Sun and Its Radiation to improve our understanding of Earth’s climate variations“, Richard C. Willson (Columbia University), on NASA’s ACRIM website, 37 slides.  I suggest starting at slide #14.

(B)  Articles (most from peer-reviewed publications) about the solar cycle appear in section 5 on the FM reference page about Science & nature – studies & reports.  They show the many sides to this, one of the least well-understood aspects of the climate sciences.

(C)  Articles about the sun from the FM site:

1. Worrying about the Sun and climate change: cycle 24 is late, 10 July 2008
2. Update: is Solar Cycle 24 late (a cooling cycle, with famines, etc)?, 15 july 2008
3. Solar Cycle 24 is still late, perhaps signalling cool weather ahead, 2 September 2008
4. Update on solar cycle 24 – and a possible period of global cooling, 1 October 2008
5. This week’s report on the news in climate science, 7 December 2008
6. Weekend reading recommenations about climate change, 13 December 2008
7. An important new article about climate change, 29 December 2008
8. About the recent conference ”Solar Activity during the onset of Solar Cycle 24″, 3 January 2009
9. NASA: Sun undergoing a “deep solar minimum”, 13 April 2009
10. The Unusually Quiet Sun finally gets some attention, 23 April 2009

Afterword

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