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On climate, these guys know their stuff

Sara Phillips, Thursday March 6, 2014 - 06:38 EDT

When Australia's two top scientific institutions release a report stating our summer heatwave wasn't caused just by natural variability, we can be confident they've got it right, writes Sara Phillips.

The weather in our nation's capital today is predicted to be 28C. Mostly sunny, with light winds.

I have no crystal ball, but I reckon it's pretty likely the Bureau of Meteorology is going to be about right. I suppose we'll find out later today.

The Bureau's website is one of the most accessed sites in Australia. Everyone wants to know whether or not to bring a brolly. The fact that it is accessed so often is testament to the fact the BoM is usually pretty reliable. Sure, we all like to whinge about the weather - particularly when showers show up unexpectedly - but by and large, you've got to admit, they do a pretty good job.

At home, I check the weather before I get up on my phone using the WiFi internet connection I have in the lounge. It's only very recently that WiFi was invented - 1996 - but Aussies are keen on technology and it's really caught on.

WiFi was invented by that other great Australian institution, the CSIRO. It wasn't the first local area network, but it worked the best of the technologies jostling for position back in the day.

Every two years, these two venerable scientific institutions team up to release a State of the Climate report.

Today on what is predicted to be a lovely day in Canberra, BoM and CSIRO scientists will be briefing relevant officials on their findings.

It's the third from the two and the results are remarkably consistent across time. The first report said that temperatures had increased 0.7C since 1960; the second stretched out to 1910 and found that temperatures had gone up 0.75C; the latest suggests it may be 0.9C since 1910.

The consistent theme here is: hotter.

In fact, in the latest report the BoM and CSIRO scientists took temperature records from 1910 to 2013. They averaged the daily maximums for locations from all around Australia. So Canberra's top of 28 would be averaged with the expected tops of 26 for Sydney, 41 for Meekatharra in outback WA and so on. Then they ranked the average national temperature from hottest to coolest. They then examined how many days each year were in the hottest 1 per cent of all the days.

The first 30 years, 1910 to 1940, had 28 days that were in the hottest one per cent of all days. Last year, in just one year, there was also 28 days that were in the hottest one per cent.

Given such a shocking increase in the frequency of uncomfortably hot days, the report concludes that "record-breaking summer temperatures in Australia over 2012-2013, are very unlikely to have been caused by natural variability alone."

In order to work out whether the weather is natural variability or could be down to climate change, scientists calculate "fraction attributable risk". It's the same mathematics that medical scientists use to work out that smoking increases your risk of lung cancer, or that being overweight increases your risk of diabetes.

The difference with the climate, is that it's just physics. Human beings and medical science have any number of factors that they can't predict. It's the classic tale of someone's grandma who smoked a pack a day and lived until she was 105.

But with climate change, they are only predicting the physical processes that determine weather: water, heat, air movement, molecules, reflection, refraction. Sure it's incredibly complex - we are talking about predicting the behaviour of molecules over the whole planet, after all - but there are fewer wildcards than when dealing with biology.

In theory, it is all predictable, if only you had a computer big enough to handle the information. In practice, there is no computer that big, so they predict with broad brushstrokes the likely future scenarios.

"Warming by 2070, compared to 1980 to 1999, is projected to be 1.0 to 2.5C for low greenhouse gas emissions and 2.2 to 5.0C for high emissions," the report notes.

In science, when you want to be right, you do the experiment again. If you get consistent results it puts a tick in the column marked "probably right". The best way to show to the world that you're onto something is to repeat the experiment again and again and come up with the same result.

Even better, get a rival scientist to do your experiment and see what their results are. Lots of ticks in the "probably right" column lends weight to your views.

Scientific papers have detailed instructions on how to run the experiment for this very reason. Scientists want other people to try to replicate their results.

Assessing climate data and making predictions about the future is not rocket science - it's far harder than that. But the consistency of the observations and predictions coming from these two trusted Australian scientific institutions is an indicator of the reliability of the information.

The BoM and CSIRO have consistently returned similar results in hundreds of experiments, which are distilled into these biannual reports.

The very best Australian science gave us WiFi and reliable weather information. The Australian people can be just as confident the climate information from these two organisations is as robust and thorough as the rest of their body of work.


© ABC 2014

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