Climate change - and concerns about rising levels of carbon dioxide in the atmosphere - are often in the headlines. However, looking back in the history of the earth, it's clear that this isn't the first time carbon dioxide levels have risen. So why should we worry now? We delve into the past to explore the effects climate change can have on the oceans and how that, in turn, can impact the climate. Plus, in the news, a new species of early human ancestor, the scientist who's jumping the Hubble queue with a helium balloon, and why humans are hard-wired for laziness...