Ice ages come and go

Spring is again long in coming this year. Months of snow has piled up along the roads in dirty heaps, while lakes and coastal bays are covered in thick ice. In spite of warm winter coats, woollen hats and thick gloves, the icy easterly wind is devastating for those who venture outside. Welcome to late 17th century Europe, at the height of a mini ice age.

Could this happen again? Astronomers predict that solar activity, and hence the Sun’s energy supply to Earth, will decrease over the next 10 years. The last time the Sun was this quiet, the Northern Hemisphere plunged into the minor ice age of 1450-1850. The coldest years werefrom 1645 to 1715, when Western Europe was held in an icy grip, with millions of people starving or freezing to death.

Scientists still disagree about what exactly caused the minor ice age – and about what was happening here in Australia at the same time. Until recently it was believed that the Southern Hemisphere also cooled but to a lesser extent, with evidence that New Zealand’s glaciers grew to their greatest size at this time. But more recent re-dating of this evidence has indicated that this happened after the Northern Hemisphere’s cooling event. Deep-sea cores suggest that