Closer Look, FAQ, Skeptics, Solar Influence

A Closer Look: The Solar Influence

Isn’t the Sun driving current climate change?

Last updated: February 9, 2009

No. Perhaps a better question would be, “Is the Sun contributing to current climate change?” In that case, the answer would be yes.

The Sun goes through a 22-year cycle consisting of two 11-year components. At the end of each of these 11-year cycles, the magnetic poles of the Sun switch, switching the hemispheric location for the magnetic north and south poles. So, it takes 22-years for the poles to return to their original positions. Through each 11-year component sunspots proceed from their maximum to their minimum, and it is this fluctuation in sunspot activity that can influence Earth. However, while it does fluctuate slightly through these cycles, the Sun’s overall irradiance (the Sun’s output) does not change significantly. If the Sun’s overall output did change and rise, scientists agree that such a rise would need to continue for decades to have a noticeable impact on Earth’s climate.

Satellite observation of the Sun’s output began in 1978, and, as you can see on the indicators page and in Figure 1 below, the output of the Sun has not increased over the 30 years of this direct observation.

Solar irradiance, 1978 to 2008Figure 1: Solar Irradiance, 1978-2004; Source: World Radiation Center

While solar output has decreased over the last 30 years, global surface and lower atmospheric temperatures have increased.

Global temperatures, 1979-2008
Figure 2: Global surface temperatures, 1979-2008; Sources: NASA GISS, HadCRUT, UAH, RSS

Also, planetary heating originating from the Sun would warm all levels of the atmosphere. Figure 3 notes the observed warming specifically of the lower troposphere near the Earth’s surface over the last 30 years.

Solar irradiance, 1978 to 2004
Figure 3: Atmospheric Temperature Anomaly, Lower Troposphere, 1979-2008; Source: RSS

However, Figure 4 notes that the stratosphere in the upper reaches of the atmosphere has experienced a concurrent cooling during the same time period. While this cooling of the upper atmosphere is inconsistent with solar heating, it is consistent with warming derived from increases in greenhouse gas concentrations.

Solar irradiance, 1978 to 2004
Figure 4: Atmospheric Temperature Anomaly, Lower Stratosphere, 1979-2008; Source: RSS


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