Over the past few decades, our Sun has been relatively
active, giving off high levels of the solar radiation that warms
the Earth. However, in recent years this peak activity has tailed
off, prompting scientists to wonder if the Sun is heading into a
period of lower output.
A new study says even if the Sun's activity did drop
off for a while, it wouldn't have much impact on rising global
temperatures. But it could mean a higher chance of a chilly winter
in Europe and the US, the researchers say.
The Sun's activity rises and falls on an approximately
11-year cycle, but it can experience longer variations from one
century to another. Over the past 10,000 years, the Sun has hit
around 30 periods of very high or very low activity - called 'grand
maxima' and 'grand minima'.
One of these occurred between 1645 and 1715, when the
Sun went through a prolonged spell of low
solar activity, known as the Maunder
Minimum. This didn't have much of an effect on global climate,
but it was linked to a number of
very cold winters in Europe.
In 2010, scientists
predicted an 8% chance that we could return to Maunder
Minimum conditions within the next 40 years.
But since that study was published, solar activity has
declined further, and this likelihood has increased to 15 or 20%,
says new research published today in open-access journal Nature
In fact, the Sun's output has declined faster than any
time in our 9,300-year record, say the researchers. And so they set
out to analyse what this could mean for global and regional
The researchers used a climate model to run two
scenarios where solar activity declines to a grand minimum. They
then compared the results with a control scenario where the Sun
continues on its regular cycle.
For all model runs they used the
RCP8.5 scenario to account for future climate
change - this is the scenario with the highest greenhouse gas
emissions of those used by the Intergovernmental Panel on Climate
IPCC). Global emissions are currently
tracking just above this
You can see the modelling results in the maps below.
Overall, a grand solar minimum could see global average temperature
rise trimmed by around 0.12C for the second half of this century,
the researchers say. Larger changes (shown as dark greens and
blues) are seen in some parts of the northern hemisphere.Projected difference in annual average
surface temperature for 2050-99 between RCP8.5 emissions scenario
and a) Solar scenario 1 and b) Solar scenario 2. Areas of blue and
green show regions projected to be cooler because of the solar
minimum. Source: Ineson, S. et al. (2015)