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Solar flare image: NASA

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Home > Climate wiki > What causes climate change? > Sunspots & solar activity

Sunspots, solar activity, cosmic rays

Summary

  • Solar activity is a natural climate forcing. When the Sun has fewer sunspots, it’s an indicator that it gives off very slightly less solar energy, that is, less heat.
  • About every 11 years the number of sunspots reaches a high and then declines.  Sometimes these ‘solar cycles’ last for longer periods. In the late 1600s, people noticed significantly fewer sunspots over a long period called the Maunder Minimum, which corresponded with slightly lower global temperatures (Fig. 2).
  • A second slightly cooler period called the Dalton Minimum also corresponded with the so-called ‘Little Ice Age‘ in Europe (Fig. 2).
  • Sunspot activity 1880 – 1970 increased slightly, matching a slight increase in temperature. However, sunspot activity subsequently declined while temperatures continued to rise significantly (Fig. 3). This indicates that any activity associated with the Sun in the past 50 years may have slightly helped offset global warming.
  • A supernovae might have helped initiate the Quaternary Period (our current Ice Age) 2.5 million years ago.
  • Miyake Events (abrupt carbon-14 spikes in the atmosphere due to solar or cosmic particle events) have no impact on climate. 

Future sunspots?

Fig. 1: Solar Cycle 25 began 2020 (Image: NOAA
Fig. 1: Solar Cycle 25 began 2020 (Image: NOAA

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Home > Climate wiki > What causes climate change? > Sunspots & solar activity

Sunspots and solar activity

Summary

  • Solar activity is a natural climate forcing. When the Sun has fewer sunspots, it’s an indicator that it gives off very slightly less solar energy, that is, less heat.
  • About every 11 years the number of sunspots reaches a high and then declines.  Sometimes these ‘solar cycles’ last for longer periods. In the late 1600s, people noticed significantly fewer sunspots over a long period called the Maunder Minimum, which corresponded with slightly lower global temperatures (Fig. 2).
  • A second slightly cooler period called the Dalton Minimum also corresponded with the so-called ‘Little Ice Age‘ in Europe (Fig. 2).
  • Sunspot activity 1880 – 1970 increased slightly, matching a slight increase in temperature. However, sunspot activity subsequently declined while temperatures continued to rise significantly (Fig. 3). This indicates that any activity associated with the Sun in the past 50 years may have slightly helped offset global warming.
  • A supernovae might have helped initiate the Quaternary Period (our current Ice Age) 2.5 million years ago.
  • Miyake Events (abrupt carbon-14 spikes in the atmosphere due to solar or cosmic particle events) have no impact on climate. 

Future sunspots?

Fig. 1: Solar Cycle 25 began 2020 (Image: NOAA
Fig. 1: Solar Cycle 25 began 2020 (Image: NOAA
Fig. 2: Changes in sunspot activity over the past 400 years. Maunder Minimum and Dalton Minimum (Image: Wikipedia)
Fig. 2: Changes in sunspot activity over the past 400 years. Maunder Minimum and Dalton Minimum (Image: Wikipedia)
Fig. 3: The above graph compares global surface temperature changes (red line) and the Sun's energy received by the Earth (yellow line) in watts (units of energy) per square metre since 1880. The lighter/thinner lines show the yearly levels while the heavier/thicker lines show the 11-year average trends. Eleven-year averages are used to reduce the year-to-year natural noise in the data, making the underlying trends more obvious. The amount of solar energy received by the Earth has followed the Sun’s natural 11-year cycle of small ups and downs with no net increase since the 1950s. Over the same period, global temperature has risen markedly. (Image: NASA)
Fig. 3: The above graph compares global surface temperature changes (red line) and the Sun’s energy received by the Earth (yellow line) in watts (units of energy) per square metre since 1880. The lighter/thinner lines show the yearly levels while the heavier/thicker lines show the 11-year average trends. Eleven-year averages are used to reduce the year-to-year natural noise in the data, making the underlying trends more obvious. The amount of solar energy received by the Earth has followed the Sun’s natural 11-year cycle of small ups and downs with no net increase since the 1950s. Over the same period, global temperature has risen markedly. (Image: NASA)

More information

Higher levels of solar activity generally results in more intense auroras