Seasonal Climate Outlook Message for October to January 2007

The bottom line

Another El Nino event Dave McRae Qld DPI&F 24/10/06

Information on ocean temperatures in the central Pacific (running eastward along the equator from the international dateline) continues to indicate a warming trend characteristic of an El Nino. As we have stated over the last six months, if this pattern persists it most likely will have a drying effect on our expected rainfall in spring and early summer as it did this winter over much of eastern Australia.

A common feature of an El Nino SST pattern is a later than normal start to the monsoon season. Its effect (or impact on expected rainfall) is usually less noticeable in mid to late summer for the northern half of Australia. For more on conditions in the Pacific try the Bureau of Meteorology at www.bom.gov.au/climate/ahead/

What is interesting is since 1990 there have been 8 identified El Nino events; 1991/92, 1992/93, 1993/94, 1994/95, 1997/98, 2002/03, 2004/05 and now 2006 which is an average of 1 every 2 years. This compares to 3 identified la Nina events; 1996/97, 1998/99 and 2000/01 which is an average of approximately 1 every 5 years.

Is the recent run of El Nino events a result of climate change? As our climate is influenced by both natural variability (eg orbital cycles, volcanic activity) and human induced environmental changes (eg greenhouse gases from power stations) it is difficult to say that individual events such as cyclones or droughts are the direct result of human induced climate change.

However it is worth noting that the 2001 Inter-governmental Panel on Climate Change Report (IPCC) stated that 'El Niño events are becoming more common' and 'more El Niño-like mean conditions' may prevail in the future. A new IPCC report is due later this year.

While not every drought is the result of an El Nino and not every El Nino brings widespread drought across Australia, an increase in the frequency of these events will impact on business, agriculture and regional communities. I do not think this means shutting up shop. What I do think it means is that now is the time to look at how to adapt our industries and practices to handle these potential changes.

Based on the current position of the MJO it would be reasonable to next expect it in early to mid November. Usually during summer stronger MJO signals can be expected. The MJO is a band of low air pressure originating off the east coast of central Africa travelling eastward across the Indian Ocean and northern Australia roughly every 30 to 60 days. Research has shown the MJO to be a useful indicator of the timing of potential rainfall events (but not amounts). For more information try www.apsru.gov.au/mjo/

Current rainfall probability maps are at www.dpi.qld.gov.au/climate or www.longpaddock.qld.gov.au and SOI updates are available on (07) 46881439. For other enquires contact the DPI&F Information Centre on 132523.