Wednesday, January 17, 2007

Australia's Climate is not Changing

Recently, the ABM produced their 2006 weather report as shown here.

They specifically go out to show that "Our Climate is Changing". Well it always does of course, but they specifically mean global warming.

With regards to rainfall they say that

Australia has experienced marked rainfall trends over the last 50 years with declines over southern and eastern Australia and increases across the northwest.

and then continue to say in the next paragraph:

The dry conditions in southern and eastern Australia in 2006 have continued the long-term rainfall deficiencies in many regions, some of which extend back more than five years.

Long term is 5 years? Has rainfall decreased in last 50 years or 5 years?

They conclude that

Aspects of this multi-year drought are highly unusual and unprecedented in many areas. Understanding the role that climate change has played in these anomalies is an area of active research.

Nice conclusion. I guess that global warming only applies to the south east of Australia.

So lets check the stats, as given directly from the ABM website:

Sure last year was very light on the rainfall, however it wasn't the lowest. This occurred in 1982. And whilst the last 5 years of rainfall in south eastern Australia have been low, it is not the lowest in the last 100 years. The period of 1940 to 1944 produced 75mm less rainfall in south eastern Australia than 2002 to 2006. But of course we are lead to believe that this is the worst drought in 1000 years, isn’t that right?

So the ABM suggest that this long term trend of 5 years is highly unusual and unprecedented. A simple analysis of the figures above show that this is far from the truth.

So have as they claim, south east Australia had significant decreasing trends in rainfall? Statistically speaking unfortunately not (t = 1.29, p = 0.2). So the ABM’s final conclusion to prove that our climate is changing with great emphasis on the current drought is, well, not true at all.

Is Australia's Climate Changing? Well not according to rainfall as the ABM suggest. Next up we'll look more closely at temperature around Australia.


Anonymous said...

Andrew Bolt, of The Herald-Sun, mentioned most of this back in November (or maybe October) 2006. It was belatedly picked up by other journalists in December. Okay, it's nothing new - but it is still nice to see some rational people who are prepared to look at the data!

Jonathan Lowe said...

yes I'm aware of Andrew Bolts work, this is different of course as it is from the Bom's 2006 analysis released in Jan. Similar tho