Read some reports of our changing climate today, and you might be convinced that we're about to enter a mini Ice Age, with decades of plummeting temperatures ahead. Here's why that's a lot of hot air.
Today, the Daily Mail report that we are "heading for a mini ice age to rival the 70-year temperature drop that saw frost fairs held on the Thames [in London, UK] in the 17th Century."
They cite a report by the Meteorological Office and the University of East Anglia Climatic Research Unit about solar cycles. Currently, we should be at a maximum in the solar cycle—Cycle 24, in fact—experiencing the most heat the sun can thrown at us. For some reason, we're not: the sun has been a little erratic in the past few years.
The report goes on to explain that there is a 92 per cent chance that the next solar cycle, and those through the next several decades, will be extremely weak. Which, they deduce, means we're headed for a deep chill. That sort of logic isn't new, though. And it's almost certainly incorrect. From Michael Marshall, the environment reporter at New Scientist:
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.
Sure, the Maunder Minimum itself is widely linked to the Little Ice Age. Newspapers like the Daily Mail love to claim that this is exactly what's going to happen again.
The problem with the argument, however, is that the sun failing to put enough heat out just doesn't make that big an impact on our already-warming planet. It's one factor among many, and a relatively minor one at that. According to New Scientist, in 2010 a team of researcher modelled what would happen if we had a global temperature minimum starting now, and running to 2100. The result? The average global temperature would drop by 0.3C at most.
On the other hand, current estimates for temperature increase due to greenhouse gas emissions are 2-4.5C by 2100. Looking at the two, warming due to greenhouse gasses wins out. In fact, the two results can happily superposed, which means we can say that the smallest change in temperature would then be a 1.7C increase.