Something weird seems to be happening to our weather - it appears to be getting more extreme. In the past few years we have shivered through two record-breaking cold winters and parts of the country have experienced intense droughts and torrential floods. It is a pattern that appears to be playing out across the globe. Hurricane chasers are recording bigger storms and in Texas, record-breaking rain has been followed by record-breaking drought. Horizon follows the scientists who are trying to understand what's been happening to our weather and investigates if these extremes are a taste of what is to come.