Spring starts in Australia this week. Are we, thanks to climate change, heading for a long hot summer, filled with extreme weather events?
Well no, I doubt it. It's just as well climate scientists have the time and ability to interpret vast quantities of weather data, because whenever I look into what I have available, I just don't see the trends to support the case.
That doesn't mean the experts are wrong (although that sometimes happens). It just makes it easier for the laymen to doubt what they say. For someone who, like me, has been sitting on the fence for a long time, it makes the whole experience very uncomfortable.
For example, the Bureau of Meteorology presents a lot of data in the climate change section of its website. It includes a graph showing the average number of hot days (over 35Â°C), which has been increasing since the late '50s. I have recreated the data here.
Temperature extremes are considered as one of the key outcomes of climate change, so it's an important set of data to look into. However, the extent of the analysis is from 1957 because, as the bureau's website points out, "digitised daily temperature series are not available at many locations until that year".
So let's look at a location for which there is a long data series. When I use the bureau's source data for recordings from Sydney's Observatory Hill I see the warming trend in Sydney is heading in the same direction. Basically, we get an extra very hot day per year.
If I take this data back 100 years you see a different picture. The 1950s to the 1970s were three decades with far fewer very hot days, but you can see the early part of the last century was a lot warmer. Add this data into the trend and the number of very hot days in Sydney is actually falling.
In February I looked at a range of other data and found that mean maximum temperatures seemed to be rising in Sydney (not the extremes), but this could be a factor of a growing city. When I looked at Dubbo, a smaller centre for which there is long time series data available, I discovered that their mean temperature was falling.
None of this leads me to believe that climate change is a con, although shock-jocks and vehement climate change deniers could easily use it for that purpose. If they want another sound-bite, 3 of the 33 days over 40Â°C in Sydney from the last 100 years happened in the last decade --- pretty close to average, so no sign of more extreme temperatures there.
All I am doing, of course, is taking a tiny slice of data from a mass available that has been analysed by scientists and subject to rigorous peer review. It shows you can take any abstract data in the climate change debate and use it to argue your stance. In reality it's no better than saying climate change is not happening because the weather was hotter when I was a youngster. If you are in your seventies that's probably true.
All I seek to demonstrate is that the subject is complex, that data is often contradictory, and there is not sufficient intelligent debate to help make sense of the matter. The Bureau of Meteorology's site, for example, tells us climate change is a problem and presents data to support its argument. But, as I have just shown, it can be easy to find a counter argument --- in this case I simply changed the timescale of the data it has presented. Departments such as this would do well to argue the pros and cons, then sceptics might engage in the discussion rather than believe they are being preached at.
Meanwhile, Spring starts in Australia this week. It's time to enjoy the climate. And who knows, it might be a hot September. A quarter of all of the September days in Sydney over 30Â°C in the last 100 years have happened since 2003. Climate change, do you think, or just a few bits of data picked to scare people?
Click here to view my Excel spreadsheet used to compile these graphs. If anyone wants to extrapolate this data further, for other centres, please do!