The Sun’s climate role confirmed

  • Date: 06/04/21
  • Dr David Whitehouse, GWPF Science Editor

“The scientific community has been unclear on the role that solar variability plays in influencing weather and climate events here on Earth. This study shows there’s reason to believe it absolutely does and why the connection may have been missed in the past.”

Top: Six-month smoothed monthly sunspot number from SILSO.  Bottom: Oceanic El Niño Index from NOAA. Red and blue boxes mark the El Niño and La Niña periods in the repeating pattern. Source: Climate Etc, September 2019

If you ask most climate scientists, they will tell you that the Sun’s small variability is unimportant when it comes to influencing climate. They may have to change their minds if a new line of research holds up. It seems that solar variability can drive climate variability on Earth on decadal timescales (the decadal climatic variability that Michael Mann recently ‘proved’ doesn’t exist). That’s the conclusion of a new study showing a correlation between the end of solar cycles and a switch from El Nino to La Nina conditions in the Pacific Ocean. It’s a result that could significantly improve the predictability of the largest El Nino and La Nina events, which have several global climate effects.

Energy from the Sun is the major driver of our entire Earth system and makes life on Earth possible,” said Scott McIntosh, of the National Center for Atmospheric Research, a co-author of the paper. “Even so, the scientific community has been unclear on the role that solar variability plays in influencing weather and climate events here on Earth. This study shows there’s reason to believe it absolutely does and why the connection may have been missed in the past.”

The approximately 11-year solar cycle – the appearance (and disappearance) of spots on the Sun – has been known for hundreds of years. In this new study, the researchers use a 22-year “clock” for solar activity derived from the Sun’s magnetic polarity cycle, which they consider a more regular alternative to the 11-year solar cycle. This research was published last year.

Coincidence unlikely

Applying this to climate studies the researchers found that the five estimates of the end of a solar cycle that occurred between 1960 and 2010-11 all coincided with a flip from an El Nino (when sea surface temperatures are warmer than average) to a La Nina (when the sea surface temperatures are cooler than average). The end of the most recent solar cycle – happening now – is also coincident with the beginning of a La Nina event. Robert Leamon of the University of Maryland-Baltimore County said, “Five consecutive terminators lining up with a switch in the El Nino oscillation is not likely to be a coincidence.”

In fact, only a 1 in 5,000 chance or less (depending on the statistical test) that all five terminator events included in the study would randomly coincide with the flip in ocean temperatures. Now that a sixth terminator event — and the corresponding start of a new solar cycle in 2020 — has also coincided with an La Nina event, the chance of a random occurrence is even more remote.

The paper does not delve into what physical connection between the Sun and Earth could be responsible for the correlation, but the authors note that there are several possibilities that warrant further study, including the influence of the Sun’s magnetic field on the number of cosmic rays that escape into the solar system and ultimately bombard Earth. However, a robust physical link between cosmic ray variations and climate has yet to be determined.

If further research can establish that there is a physical connection and that changes on the Sun are truly causing variability in the oceans, then we may be able to improve our ability to predict El Nino and La Nina events,” McIntosh said.

Feedback: david.whitehouse@thegwpf.com

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