A change in the air

By Andrew Stokes

Thursday 1st August 2002

Recent weather patterns indicate another El Ni�o is brewing. Our primary producers could be in for a storm, reports Andrew Stokes

What have poor sales of Peruvian alpaca sweaters got to do with masses of dead eels in Canterbury lakes, crazed termites in the Arizona desert and an upsurge of malaria cases in Kenya? They have all been linked to a weather phenomenon that hit the globe in 1997/98: a climatic event that goes by the name of El Ni�o and has been blamed for more bad karma than the management of New Zealand rugby.

In the tradition of chaos theory's favourite insect, the butterfly that beats its wings in China and causes a sequence of events that leads to an earthquake in California, the impact of an El Ni�o can be felt in a multiplicity of unexpected ways. The last one to hit New Zealand was deemed responsible for cutting the nation's GDP by nearly $1 billion over three years, mainly through lost agricultural production during the droughts of 1997/98 and 1998/99, and its effects on reliant industries. And it may just be about to happen again.

Peruvian fishermen in the late 1800s first coined the term El Ni�o ("Christ child" in Spanish) to describe the warmer currents experienced near Peru at Christmas. That warming is now seen as part of a wider phenomenon of variations in sea surface temperature across the Pacific and associated changes in wind direction and sea levels. Its progress can be measured in the southern oscillation index (giving rise to the term Enso, or El Ni�o southern oscillation), which measures shifts in surface air pressure at Darwin in northern Australia and Tahiti. If air pressure is higher at Darwin, the index is negative. Consistently negative readings point to an El Ni�o in the making. At the time of writing, the index had recorded negative values for three months in a row, the Australian Bureau of Meteorology had forecast a 70% to 90% chance of an El Ni�o and Australia's crop production forecasts had been slashed.

What could this mean for New Zealand? A review of the 1997/98 El Ni�o by Dr Reid Basher of the National Institute of Water and Atmospheric Research (NIWA) says it is characterised by more southerly winds in winters, more south-westerly winds in spring and autumn and more westerlies in summer. The west coast gets even wetter, while ponds dry up on the east coast. Back then there were significant losses of pasture and water reserves and in animal, grain and fruit production. (Although it wasn't all bad, with a reduced need for chemical pest control and a better grape crop.) Look at the GDP figures for the past five years and there's a noticeable dip in late 1997 and most of 1998, with the primary industry sector a big negative contributor. No one wants that to happen again, or worse, a repeat of the monster El Ni�o of 1982/83.

How bad was it really?

Bank of New Zealand chief economist Tony Alexander reckons the economic effects of the last El Ni�o may have been overstated: the economy had also been hit by a combination of the Asian crisis, high interest rates, a fall-off in migration and an end to the housing boom. Isolating the specific El Ni�o contribution isn't easy.

While acknowledging the negative readings on the southern oscillation index, Alexander says it's too early to hit the panic button until we see a few more months of bad figures that could then lead to some implications for economic growth. Although the southern oscillation index was at -14.5 in May, it improved to -6.3 in June. "With any luck, this backs up the view of some meteorologists that this El Ni�o period will be a minor one," Alexander says.

He sees the most vulnerable as those who got caught up in the recent dairy boom and expanded into more drought-prone areas. It will only take a small cut in production to hit them hard.

It's common sense to say that those primary producers who haven't prepared for climatic change should do so with urgency, particularly in areas hit hard before such as Marlborough, North Canterbury and parts of the Wairarapa. There have been some encouraging developments in recent years in terms of sustainable land use - better stock and irrigation management, improved use of fertiliser and planting and harvesting regimes - that have focused on preventing moisture loss and minimised the impact of dry spells. That trend is also providing some comfort in Australia, where the latest farming equipment is allowing farmers to make the most of any rain.

For anyone with access to the internet, becoming an El Ni�o bore is easy. NIWA's site has an incredible range of information (www.niwa.cri.nz/rc/atmos/clivar/elnino) and explanations, and links to the latest measures of all the factors that can indicate an El Ni�o in the making. Those who wish to be pioneers could look at investing in weather derivatives - financial products that allow users to hedge against weather movements - being offered by Macquarie Bank in Australia. Ted Robson of Macquarie says that more people are looking at derivatives because of an El Ni�o, but many want to "wait until an El Ni�o is certain and then attempt to put in place some hedging". By this time, however, it is too late, "as no weather derivatives provider is going to stand in front of an express train." The message is clear, start preparing now. You can't blame everything on an El Ni�o.

In brief

Sea surface temperatures continue to be around 1�C above average across much of the equatorial Pacific. This state is consistent with a developing El Ni�o.
Subsurface data for June show marked warming in the central and eastern Pacific.
Eight computer models out of 11 surveyed predict central to eastern Pacific conditions in the late 2002–early 2003 period to be sufficiently warm as to be classed as an El Ni�o.
The SOI rose in June to a value of -6, nine points above the May value of -15.
Cloudiness around the dateline in the central Pacific has increased.
Easterly trade winds have weakened and reversed (ie turned westerly) in the western Pacific.

Andrew Stokes
arstokes@xtra.co.nz

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