Monday, June 18, 2007

South East Queensland Drought

So much has been talked about the drought of recent, and how it's all global warming that is the main cause. Queensland's water reserves are the worst hit and luckily this year we've seen a good increase in rain. But was global warming really the cause?

Shown below is the rainfall for south east Queensland. As one can clearly see, the amount of rainfall in the last 6 years has been well under par by as much as 40mm per month - ouch!



But if we ignore this recent downward trend, well, there seems to be no trend at all. Seems very random. Either something has happened only in the last 6 years so that the area has less rainfall, or this too, is somewhat random.

Either way, if global warming was the cause, it seems as though global warming has only been around this area in the last 6 years, and then thankfully this month is now non existent.

5 comments:

Anonymous said...

tipping points?

There are points at which weather system paths change suddenly, not slowly over time. Which would look like an abrupt change not a slow change.

Jonathan Lowe said...

well from 1973 to 1977 we had a tipping point where we gained heaps of rain, and then, as expected went back to normal....strange that.

Alan Woods said...

Seems to be a reasonable correlation there between rainfall values and the PDO.

http://jisao.washington.edu/pdo/img/pdo_latest.png

So is it climate change, or climate cycles? Bet you won't here Flannery talking about the PDO. he prefers the 'Asian Haze'.

John M said...

I think you'll find a pretty good correlation to the Southern Oscillation Index available at http://www.bom.gov.au/climate/current/soihtm1.shtml. Don't forget that both conditions are likely to have short-term abnormalities (such as tropical storms or very heavy rainfall) and these will distort the picture.

The Bureau of Meteorology also says "El Niño is not a freak of climate, it's not a rogue weather phenomenon, and it isn't in any way abnormal. ... More often than not, El Niño events result in reduced rainfall across parts of eastern and northern Australia, particularly during winter, spring and early summer. However, the precise nature (where and when) of the impact differs quite markedly from one event to another, even with similar changes and patterns in the Pacific Ocean." (see http://www.bom.gov.au/climate/enso/)

philip said...

It looks like the big anomalies are on the +ve side with more but smaller anomalies on the -ve side.

I'll guess that the +ve anomaly years are when a cyclone or remnants hit.

Which leaves the last six years as fairly typical (normal) for non-cyclonic event years.

The last 7 years have been below average for cyclones in Australia.

Queenslanders should be hoping the AGW believers are right and AGW will cause more extreme and intense weather, i.e. more cyclones, because normal rainfall* seems to be a problem for them.

* Normal and average, frequently used as synonyms, are most definitely not the same thing.