The Sun could emit less radiation by mid-century, giving planet Earth a chance to warm up a little more slowly, but not to halt the trend of human-induced climate change.
This was pointed out by an investigation by the Scripps Institution of Oceanography at the University of California, San Diego, published at the end of 2017. For this team of scientists, the cooling would be the result of what they call a great minimum, a periodic event during which the Sun’s magnetism decreases, sunspots form infrequently, and less ultraviolet radiation reaches the planet’s surface.
Before analyzing the consequences that it will have on our planet, we are going to comment on why this period of less activity on the part of the star king occurs.
Scientists believe the event is triggered at irregular intervals by random fluctuations related to the Sun’s magnetic field.
There is a well-known 11-year cycle in which the Sun’s ultraviolet radiation peaks and declines as a result of sunspot activity.
During a great minimum, called the Maunder minimum, ultraviolet radiation decreases an additional 7% beyond the lowest point of that cycle. And this is what will happen by the year 2050, according to the researchers, after reviewing almost 20 years of data collected by the International Ultraviolet Explorer mission.
The results point to a high probability of a large minimum on this date, because the sunspot pattern of recent solar cycles resembles the escalations of past large minimum events.
The river Thames and the Baltic Sea, frozen
In fact, another Maunder minimum took place on Earth in the mid-17th century.
At that time, temperatures were low enough to regularly freeze the River Thames and freeze the Baltic Sea to such an extent that a Swedish army was able to invade Denmark in 1658 by walking on foot across sea ice.
Scientists are not sure if the same will happen by 2050 , but it is a reference. “Now we have a reference point from which we can perform better climate model simulations”, is extracted from the scientific document. “So we can get a better idea of how changes in solar UV radiation affect climate change.”
What consequences will this cooling have for our planet?
The reduced energy from the Sun sets off a series of events on Earth, beginning with a thinning of the stratospheric ozone layer.
That thinning, in turn, will change the temperature structure of the stratosphere, which will then alter the dynamics of the lower atmosphere, especially wind and weather patterns.
The cooling will not be uniform. While certain areas of Europe cooled down during the last Maunder Low, other areas such as Alaska and southern Greenland warmed accordingly.
Despite how much the Maunder minimum may have affected Earth last time, the researchers predict that further cooling would not stop the current trend of global warming, but could slow it down a bit.
After all, the cooling effect produced by a large 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 the air, the greenhouse gas concentration is now more than 400 parts per million, continuing an increase that began in the Industrial Revolution.
Other events that can cool the Earth
In turn, other researchers have used models to estimate what event similar to a Maunder minimum, if it occurred in the next few decades, could be significant for our current climate, which is now warming rapidly.
One of these studies analyzed the climatic consequences of a large solar minimum assuming total solar irradiation reduced to 0.25% over a 50-year period between 2020 and 2070.
This study found that after the initial decline in solar radiation in 2020, the global average surface air temperature would cool down to several tenths of a degree Celsius. However, by the end of the great solar minimum, the warming in the simulated Maunder minimum model had almost reached the benchmark simulation.
This reinforces the idea that a future great solar minimum could slow, but not stop, global warming.
Dan Lubin et al. Ultraviolet Flux Decrease Under a Grand Minimum from IUE Short-wavelength Observation of Solar Analogs, The Astrophysical Journal (2017). DOI: 10.3847 / 2041-8213 / aaa124
