The Canberra fires of 2003: a pine planataion on the edge of the Brindebella Ranges ignites
Credit: SMH
The precise mechanism driving an El Niño year is complex and still not fully understood, and the cycles are not entirely predictable. But in the late 1980s Neville Nicholls, a climatologist at Australia's Bureau of Meteorology, pointed out that the pressure difference between highs over Darwin, in the Northern Territory, and lows over the island of Tahiti has been a good historical indicator of whether an El Niño was either underway or about to begin.
That difference, Nicholls suggested, could serve to forecast future Australian droughts; the more negative the index, the greater the likelihood of a drought. Now known as the Southern Oscillation Index, it has become so widely accepted that it is misused for short-term forecasting: the index is often part of television weather reports.
Climatologists are still seeking the answers to two big questions. Firstly, what drives the frequency of the switches from hot, dry El Niño years to moist La Niña ones over the centuries? And secondly, what causes the varying intensities of the events? Longer cycles, in which one or the other extreme predominates, apparently exist; explaining those would go a long way to predicting whether, say, one wet year after a five-year drought signals only temporary relief or marks the beginning of multi-year wet period.
There is, of course, a third question. Why are the extremes becoming more extreme? Why are the wet phases becoming wetter, and the warmer phases becoming drier and more beset by fire? Global warming seems a prime suspect. "Among scientists, there's no real question about whether global warming exists," says Barnett. "The only questions are more a matter of how much and how fast, and what its specific impacts are in a given area.
The debate about global warming is over, at least among rational people."
According to the Intergovernmental Panel on Climate Change - a respected group of leading scientists established by the World Meteorological Organisation and the United Nations Environment Program - the past decade included five of the hottest years since accurate meteorological records began to be kept in the 19th century.
Worldwide, September 2005 was the warmest month on record, according to the U.S. National Oceanic and Atmospheric Administration. And 2005 will be the second or third warmest year on record globally, Britain's national weather service said in October.
"Whether it is second or third depends on how Siberia reacts between now and the end of the year," said Wayne Elliott, a spokesman the Met Office. "1998 was the warmest ever, 2005 is looking at being second. It will be another very warm year generally, which is in line with global climate-change research."
Based on British measurements of temperatures on land and sea going back to 1861, the world's second hottest year was 2002, followed by 2003, 2004 and 2001. It's not merely a scientific curiosity: this year, Portugal and Spain have experienced their worst droughts ever as well as crippling wildfires; while further east, floods and torrential rain drenched Switzerland, Germany, Austria, Bulgaria and Romania. It's more evidence that global warming is caused, at least in part, by human activities.
