A fall in the sun’s heat output to levels last felt 300 years ago would slow temperature rises in the eastern United States and Europe, though the worldwide impact would be far too small to halt global warming, a study said on Tuesday.
The report, led by scientists at the British Met Office Hadley Centre, said the possibility of a dimmer sun should be added to regional plans for coping with more winter floods, likely because of more rain and fewer frosts in a warmer world.
The study said solar output was falling from high levels in recent decades and there was a 15-20 percent chance of a decline by 2050 to match the “Maunder Minimum” of 1645-1715, the depths of a Little Ice Age when the River Thames in London froze over.
Such a natural dimming of the sun would cause a 0.1 degree Celsius (0.2 Fahrenheit) fall in average global temperatures, they estimated, a tiny brake on a 6.6C (11.9F) rise in the worst case scenario of man-made global warming by 2100.
“We can’t be saved by the sun, unfortunately,” professor Adam Scaife, a co-author at the Met Office Hadley Centre in Britain, told Reuters, commenting on the report published in the journal Nature Communications.
Even so, a new Maunder Minimum would have noticeable regional impacts in the eastern United States, Iceland and northern and eastern Europe, slowing a rise in temperatures by between 0.4 and 0.8C (0.7 and 1.4F), the report said.
Such places were likely to be kept slightly cooler because computer models suggested a big fall in solar activity would disrupt winds and suck cold air southwards from the Arctic.
“The new aspect is the regional effects, particularly in Europe in winter,” said Georg Fuelner, an expert at the Potsdam Institute for Climate Impact Research who was not involved in the study.
“These (regional) effects are interesting but we need to see how robust they will be with future follow-up studies,” he told Reuters.
Fuelner wrote a 2010 study showing that the impact of any Maunder Minimum would also be marginal compared to global warming.
Tuesday’s report said the local impacts of a dimmer sun on Europe and the United States were big enough to warrant inclusion in long-term infrastructure plans, such as storm drains in cities or river flood defences.
“Engineers need to know the full range of uncertainties,” Scaife said.