Global Warming vs. Solar Cooling: The Showdown Begins in 2020

The sun may be dimming, temporarily. Don’t panic; Earth is not going to freeze over. But will the resulting cooling put a dent in the global warming trend?

A periodic solar event called a “grand minimum” could overtake the sun perhaps as soon as 2020 and lasting through 2070, resulting in diminished magnetism, infrequent sunspot production and less ultraviolet (UV) radiation reaching Earth — all bringing a cooler period to the planet that may span 50 years.

The last grand-minimum event — a disruption of the sun’s 11-year cycle of variable sunspot activity — happened in the mid-17th century. Known as the Maunder Minimum, it occurred between 1645 and 1715, during a longer span of time when parts of the world became so cold that the period was called the Little Ice Age, which lasted from about 1300 to 1850.

But it’s unlikely that we’ll see a return to the extreme cold from centuries ago, researchers reported in a new study. Since the Maunder Minimum, global average temperatures have been on the rise, driven by climate change. Though a new decades-long dip in solar radiation could slow global warming somewhat, it wouldn’t be by much, the researchers’ simulations demonstrated. And by the end of the incoming cooling period, temperatures would have bounced back from the temporary cooldown.

Sunspots, which appear as dark patches on the solar surface, form where the sun’s magnetic field is unusually strong, and the number of sunspots waxes and wanes in a cycle that lasts about 11 years, fueled by fluctuations in the sun’s magnetic field.

But during the late 17th century, the sun’s spots all but disappeared. This episode corresponded with a period of exceptional cold in parts of the world, which scientists have explained as being connected to the changes in solar activity.

Sunspot activity was high in 2014 and has been dipping ever since, as the sun moves toward the low end of its 11-year cycle, known as the solar minimum, NASA reported in June 2017. But a pattern of ever-decreasing sunspots over recent solar cycles resembles patterns from the past that preceded grand-minimum events. This similarity hints that another such event may be fast approaching, the researchers reported in the study.