June 15, 2013
A few years ago, talking about weather and climate change in the same breath was a cardinal sin for scientists. Now it’s become impossible to have a conversation about the weather without discussing wider climate trends, according to researchers who prepared the Australian Climate Commission’s latest report. The report, The Angry Summer, says that behind the litany of heat and rainfall records, a clear pattern has emerged. ”Statistically, there is a one in 500 chance that we are talking about natural variation causing all these new records,” said Will Steffen, the report’s lead author and director of the Australian National University’s climate change institute. ”Not too many people would want to put their life savings on a 500-to-1 horse.” The statistic comes from tallying known weather records from around the world, and measuring the likelihood of record-breaking extremes happening without the influence of extra energy accumulating on Earth due to the build-up of greenhouse gases. ”We are talking about a massive amount of additional energy, most of which is being held around the surface layers of the ocean, which is driving the increased evaporation and rainfall,” Professor Steffen said. The tumbling of records has also prompted conversations in the scientific community to turn a corner, he said. Previously, ”weather is not climate” was the mantra, but now the additional boost from greenhouse gases was influencing every event. ”I think the steroids analogy is a useful one,” Professor Steffen said. ”Steroids do not create elite athletes – they are already very good athletes. What happens when athletes start taking steroids is that suddenly the same athletes are breaking more records, more often. We are seeing a similar process with the Earth’s climate.” This summer was the hottest on Australian record. In the 102 years of uniform national records, there have been 21 days where the continent averaged more than 39 degrees, and eight of those took place this year. Rainfall extremes have smashed records, with rain contributing more to floods and less to watering crops. The effects have continued into autumn.