Temperatures keep rising

During each interglacial period there are mini ice ages and interglacials. At the end of the last ice age, temperatures started to rise. By 4,000BC the Earth was about two degrees Celsius hotter than it is today. This period was then followed by a mini ice age. By 500BC the Earth's climate had cooled and was generally about three degrees Celsius lower than it is today.

Similarly, a particularly warm time called the Medieval Optima lasted from the 10th to 14th century, which in turn was followed by a cold period called The Little Ice Age. By the middle of the 1600s glaciers were growing rapidly worldwide, causing increasingly wintry conditions. In the early 1800s, winters were so severe that China lost its famous Jiangxi province orange crop, Sydney residents enjoyed snowy streets for the first time in recorded history and the population of Iceland fell by a half.