Question: What causes ice ages

Christina Pagel answered on 28 Jun 2013:

technically we’re still in an ice age that started 2.5 million years ago!! as long as there are permanent large sheets of ice at the Earth’s poles, the earth is in an ice age. It’s just much less cold now than it was at the height of this ice age when the ice sheets stretched down into northern france!

Apparently, the exact cause of ice ages is not known but various things affect when they happen (and when you get very cold and warmer periods within them) – these are things like atmospheric composition (how much greenhouse gas you’ve got like methan or CO2), our orbital cycle (how far earth is from the sun varies slightly over time), the movement of tectonic plates (continents) – these can change sea currents and wind patterns which are important for global temperatures …

there’s debate on when the next colder period is due – some people think in 1000 years others up to 50000 years away – and no one knows how much it will be offset by global warming!

The thing with global climate is that there are lots of feedback effects – so you can get runaway cooling and runaway heating too…