No, Earth Is Not About to Plunge Into a 'Mini Ice Age'

Image: NASA

Science journalism is hard. The job entails reading complex papers on unfamiliar, often arcane topics, and quickly becoming expert enough to succinctly explain those topics to your fellow laypeople. But on another level, the job is very straightforward: Find facts, and report them.

Unfortunately, a number of takes and headlines regarding a new study on solar cycles had very little to do with fact-finding.


By mid-century, our Sun might emit less UV radiation than it does today, and scientists just quantified how much less in a new paper in Astrophysical Journal Letters. The potential solar cool-off would be the result of a so-called Grand Minimum, a period in which the Sun’s magnetic activity diminishes to levels lower than is typical during a solar cycle, which takes about 11 Earth years and is characterized by increasing and decreasing amounts of solar activity.

This won’t, as the scientists made clear in a news release issued last week, halt human-caused climate change. There’s certainly no evidence to suggest it will plunge our planet into a ‘mini ice age.’

You wouldn’t know that from the headlines, though.

Image: Google

Sites ranging from the usual science-mangling British tabloids to more mainstream science news outlets seemed keen to suggest that the potential upcoming Grand Minimum could make a dramatic dent in global warming, if not reverse the trend entirely. That’s despite the fact that in the press release everybody aggregated, the scientists straight up said this wasn’t a takeaway of their work.

As an observer of the science newsverse, this was depressing but not entirely surprising. Studies on our all-powerful Sun are often wildly misinterpreted by the media—in fact, we’ve seen versions of this exact same news cycle play out before. The idea that global climate swings are controlled by the Sun is also a zombie talking point among climate deniers.


What the study actually did was use two decades of observations of 33 other Sun-like stars to estimate how much our star’s UV output could dip during a future Grand Minimum. The answer? UV flux levels could drop an additional seven percent beneath their typical solar cycle low.


As for how this could affect temperatures here on Earth, here’s a relevant passage from the news release, which follows a discussion of the Maunder Minimum, a period in the 17th century during which global average temperatures did dip, likely because of an earlier Grand Minimum:

Despite how much the Maunder Minimum might have affected Earth the last time, Lubin said that an upcoming event would not stop the current trend of planetary warming but might slow it somewhat. The cooling effect of a grand minimum is only a fraction of the warming effect caused by the increasing concentration of carbon dioxide in the atmosphere. After hundreds of thousands of years of CO2 levels never exceeding 300 parts per million in air, the concentration of the greenhouse gas is now over 400 parts per million, continuing a rise that began with the Industrial Revolution.


Thus, a main conclusion of the study is that “a future grand solar minimum could slow down but not stop global warming.”


In the paper (which does not mention global warming), the authors acknowledge their study is limited by a small sample size and potential data quality issues, and that other studies have reached different estimates of how much a Grand Minimum would affect UV flux.

At least one scientist has a more fundamental concern. Scott McIntosh, solar physicist at the National Center for Atmospheric Research in Boulder, Colorado, told Earther he doesn’t think examining other stars is a great way to predict what’ll happen with our Sun, for the simple reason that our measurements of other stars aren’t all that great.


“These astronomers have done what looks like a really detailed job,” McIntosh said. “The problem is they talk about Sun-like stars. And that’s kinda like comparing a zebra and a horse from a thousand miles away.”

Estimates of how much the Sun’s activity can or will change in the future aside, there’s also no guarantee that we will reach a Grand Minimum by mid-century. This was not something the study aimed to address.


In short: This study study was an incremental step toward a better understanding of solar minima, and it probably didn’t warrant a press release. It also didn’t deserve the coverage it received.

Maddie Stone is a freelancer based in Philadelphia.

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