This week I dusted off my coat and threw it on as I experienced my first chilly night in months. I expect the weather to change with the seasons, I expect autumn to be colder than summer, but this week questions have been asked about New Zealand's long-term climate, how changes that are already under way could have significant implications for New Zealand's prosperity and how we might be fudging the numbers to make ourselves look more green than we actually are.
The Earth's climate does change, and over the past 4.5 billion years it has naturally fluctuated between being very cold and covered in ice, to very hot and dry.
Earth's distance to the sun, volcanic eruptions and tectonic plate movement are all natural causes of climate change. However, over the past 50-100 years, increasing industrialisation has led scientists to believe that human activities, such as driving cars, farming, burning coal and cutting down forests, are producing greenhouses gases and artificially affecting our natural climate balance.
Scientists have measured greenhouse gases - including carbon dioxide, methane and nitrous oxide - released into our atmosphere and can show using Antarctic ice core dating that recent increases are happening at an unprecedented rate.
Greenhouse gases specifically are a concern because they can wrap a gaseous blanket around the Earth, trapping in the sun's heat and warming up our planet.