New ice age? Don't count on it

If you believe the world's newspapers today, the sun is about to send Earth into another "Little Ice Age", cooling the planet and reprieving us from global warming.
Don't believe the world's newspapers.
The reality is that, while the sun may well be about to give us a shove in the direction of cool temperatures, the evidence suggests it won't be anything like enough to drown out the warming effects of our greenhouse gas emissions.
BERLIN - JANUARY 23: Different snowmen are pic...Image by Getty Images via @daylife
It's beyond doubt that the sun has been acting rather oddly over the last few years. Ordinarily, its activity varies over about 11 years, but since 2007 it seems to have stalled.
This week a string of researchers presented new data showing that the sun still isn't perking up. That means, rather than having a solar maximum in 2013, we might not see one for a long time. Instead, the sun could go into a prolonged lull lasting several decades.
This has happened before, the most famous example being the Maunder Minimum of 1645-1715 when the sun became less luminous than normal and hardly any sunspots were seen on its surface. There is plenty of evidence that such "grand minima" cool the Earth: it's one of the more dramatic effects the sun's changing activity can have on our climate. The Maunder Minimum itself is widely linked to the Little Ice Age.
Here's where the story lurches away from reality. According to the Global Warming Policy Foundation (of whom more here), the sun's shutdown means that:

The Earth - far from facing a global warming problem - is actually headed into a mini ice age
This idea has been picked up worldwide, as a sample of headlines shows.
There's a simple problem with this claim. Let's assume that grand minima really do cool Earth's climate: not every climate scientist is convinced of that, but for the sake of argument let's go with it. Now the question becomes: how much do they cool it, and for how long?
The straightforward answer is: not enough. Last year researchers modelled what would happen to global temperatures if a grand minimum started now and continued until 2100. They found that it would lower temperatures by 0.3 °C at most.
That's not enough to compensate for our greenhouse gas emissions, which are set to raise temperatures by 2-4.5 °C by 2100. So in the most optimistic scenario, in which the grand minimum has the biggest effect possible and emissions their smallest, a rise of 2 °C would be reduced to 1.7 °C.
That isn't a new ice age: it's a slightly less severe heatwave.

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