Skip to main content
Search IntMath

Earth Day and the Southern Oscillation Index

By Murray Bourne, 22 Apr 2007

Australia is in dire straits, suffering the worst drought in 100 years. The government plans to turn off the irrigation taps in Apr 2007, because there is not enough water in the most important river system, the Murray-Darling.

The Southern Oscillation Index is closely followed by farmers in Australia. The SOI is a measure of pressure differences between Tahiti and Darwin.

If the SOI is negative, an El Niño event occurs, characterised by hot, dry conditions in Australia and wet conditions in South America. If the SOI is positive, a La Niña event occurs, and Australia tends to be wet while South America is dry.

Here is the chart of the SOI since 2002. The SOI has been negative for much of 2006, hence Australia has been in drought.

SOI 2002 to 2007
Source: BOM Australia

What is strange is that Singapore in 06/07 had the wettest Dec-Jan period we have ever experienced in the 10 years we've been living here. When you compare that to the 1997/98 El Niño, it was a very different situation:

SOI 1993 to 2000
Source: BOM Australia

Across South East Asia there were terrible periods of smoke haze in late 1997 through into 1998. It was very hot (37°C) and dry and we didn't see the sun clearly for months.

Notice how the SOI is less clearly defined in the more recent chart above. I wonder if it is due to global warming.

Back to Australia's current situation

Australia is the driest continent in the world and has mismanaged water supplies for most of the 220 years of European settlement. If they do turn off the taps, the price of food will sky-rocket. As an indication of what could happen, when the banana crop was wiped out by cyclone Larry in Mar 2006, the price of bananas went up 5-fold.

It is possible that Australia will have to import food, which is quite shocking to me. Australia is a major exporter of foods. Indeed, much of what we eat in Singapore is imported from there.

So, Prime Minister Howard, will you finally sign the Kyoto Protocol?

Happy Earth Day.

See the 1 Comment below.

One Comment on “Earth Day and the Southern Oscillation Index”

  1. Steven says:

    Thanks for this interesting article, Zac. It's scary that Australia is bone dry.

    I hope they get serious about climate change.

Leave a comment

Comment Preview

HTML: You can use simple tags like <b>, <a href="...">, etc.

To enter math, you can can either:

  1. Use simple calculator-like input in the following format (surround your math in backticks, or qq on tablet or phone):
    `a^2 = sqrt(b^2 + c^2)`
    (See more on ASCIIMath syntax); or
  2. Use simple LaTeX in the following format. Surround your math with \( and \).
    \( \int g dx = \sqrt{\frac{a}{b}} \)
    (This is standard simple LaTeX.)

NOTE: You can mix both types of math entry in your comment.


Tips, tricks, lessons, and tutoring to help reduce test anxiety and move to the top of the class.