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Are the Ice Ages linked to changes in solar radiation?

Published: 6th Jan, 2022

  • Solar radiation received at the Earth can vary by means that are unrelated to any changes on the Sun itself.
  • The best studied of these are very long term changes in the Earth’s orbit around the Sun, which alter the distribution of sunlight both geographically and seasonally.
  • They are now believed to trigger the coming and going of the major Ice Ages.
  • As such, they may provide a powerful demonstration of the impacts of changes in solar radiation on the climate system.
  • The size as well as the number of sunspots attains maximum value at every 11 years.
  • Sunspots and other forms of solar activity are produced by magnetic fields, whose changes also affect the radiation that the sun emits, including its distribution among shorter and longer wavelengths.
  • The earth has a magnetic field with north and south poles.
  • The magnetic field of the earth is enclosed in a region surrounding the earth called the magnetosphere.
  • Due to change in magnetic field of the sun, earth’s magnetic field might get affected which consequently affects the weather because the magnetosphere prevents most of the particles from the sun, carried in solar wind from impacting the earth.
  • Judith Lean and David Rind of NASA had first attempted to correlate the sun with the climate, whose interests are in modelling the sensitivity of the atmosphere and climate to different forcings.
  • Subsequently Solanki, S.K., Schussler, M. and Fligge, M. of Max Plank Institute, Germany published their findings in Nature Journal in 2000.
  • Between 1850 and 1990 the global mean temperature at the surface of the earth was warmed by approximately 0.5° C (about 1° F).
  • During the same period, the amount of carbon dioxide measured in the earth’s atmosphere increased by about 25 percent, as a consequence of our ever- increasing use of fossil fuels.
  • This raises the possibility that the two trends are directly connected, and that the century-long warming is a long- anticipated sign of the climate system’s response to human activities
  • Like the concentrations of greenhouse gases, solar activity has risen systematically through the past 100 years, as recorded in the number of sunspots.
  • The sensitivity of climate to solar radiation changes, as defined earlier, is not well known.
  • A conservative estimate is that a 0.1 percent change in solar total radiation will bring about a temperature response of 0.06 to 0.2°C, providing the change persists long enough for the climate system to adjust. This could take ten to 100 years.
  • Changes in visible and infrared solar radiation alter the surface temperature by simple heating; other parts of the spectrum can also affect climate, through paths that are less direct.
  • An assortment of recent and historical data, including those from ice-cores, corals, and the instrumental weather record, do reveal climatic variations with periods of about eleven years.
  • A possible solar connection is also often discounted on the basis that climatic events of ten to twelve years duration are neither globally distributed nor always in phase with the ups and downs of the solar cycle.

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