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El Niño: The Philippines places eight provinces under state of calamity due to drought

By Shirley Escalante in Manila, staff
26 May 2015


PHOTO: Farmers say forty per cent of their crops have been affected by the drought. (Reuters: Romeo Ranoco)

The Philippines has placed eight provinces under a state of calamity due to a drought caused by the El Niño weather phenomenon.

The central Philippines province of Cebu is the latest addition to the list of areas which have been severely impacted by El Niño.

A state of emergency allows its officials to use five per cent of more than $US2 million in local emergency funds to compensate for the losses of farmers.

Meteorologists say more than 50 provinces were beginning to suffer from the effects of the El Niño phenomenon.

They said the onset of the rainy season next month may not alleviate the impact of the drought.

Scientists at Australia's weather bureau this month officially declared a major El Niño event due to an increase in sea surface temperatures in the Pacific Ocean.

It is likely to bring hotter temperatures and lower rainfall to much of eastern Australia.

http://www.abc.net.au/

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El Niño also results in a hotter average temperature for the whole planet by about 0.1 to 0.2 degrees, because the associated change in winds lead to the release of heat from the ocean to the atmosphere.

The two strongest El Niños that we know of were in 1982-83 and 1997-98. Dubbed 'super El Niños', both these events had significant global impacts.



"In 1982-83, Australia suffered one of the biggest droughts and we had the Ash Wednesday bushfires and Melbourne was covered by the dust storm," says Cai.

"In 1997, over 23,000 people were killed due to extreme events, droughts, floods, cyclones."



The 1982 El Niño caught countries around the Pacific completely unaware and prompted data gathering and research that lead to our current understanding of El Niño, says Cai.

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During an El Niño the temperature gradient is reduced, and the water in the eastern Pacific is warmer than normal.

But what causes an El Niño to start "is the subject of debate," says Cai.

"One of the scenarios is that a little bit of weakening in the easterly wind would make the warm water flow to the east, and once it flows to the east then the temperature gradient across the Pacific changes."

The wind may return to a normal pattern, but the ocean has a longer memory and is slower to recover. And before the ocean recovers, another weather event may occur that changes the wind again.

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What's happening now?

Current indications are that we are heading towards an El Niño later in 2014 but this won't be confirmed for another couple of months.

"At the moment we're seeing the development of westerly wind and warmer temperatures in the equatorial western pacific and so that's why scientists are predicting an El Niño in the upcoming months," says Cai.

In addition to ocean temperatures and wind directions, scientists also monitor an atmospheric indicator called the Southern Oscillation Index (SOI) — which is defined as the air pressure at Tahiti minus the air pressure at Darwin, and is often reported on the news.

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"And that allowed us to put that information into our models to predict what is coming up in the coming months. And so the El Niño understanding of the ocean really started in the early 80s after that big El Niño."

Unfortunately, the 70 moorings or buoys that make up the ocean monitoring system are in jeopardy.



"Around four to five years ago when the US economy went downhill they decommissioned the ship that goes to service the buoys, so now the buoys are returning data at around 40 per cent. And that really is a pity because that system really revolutionised our understanding of ENSO science," says Cai.

This will make it harder to predict coming El Niños as other existing systems are not as good. However, the US has committed to build the buoys up again to a data returning rate of more than 80 per cent, says Cai.

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Another important factor in understanding the severity of an El Niño in Australia is the Indian Ocean dipole, a measure of sea surface temperature difference in the Indian Ocean.

The Indian Ocean dipole, in its positive phase, features cooler than usual ocean temperatures in the eastern Indian Ocean. This results in reduced rainfall in southern Australia and south eastern Australia — and subsequently drought and bushfires.

"Our bushfires are actually preconditioned by the Indian Ocean dipole, if there is an Indian Ocean dipole then the bushfire season will be more severe," says Cai.

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Why is one side of the Pacific warming faster than the other?

As the ocean gets hotter it evaporates more, which in turn cools it down slightly — just as sweating cools down a hot person. This is called evaporative cooling, and its effectiveness increases with temperature. Adding one degree of warming to both sides of the ocean will result in more evaporative cooling on the warmer western side, effectively dampening the warming there.

"If the mean temperature in the eastern Pacific is 22 then add one degree and it becomes 23. In the western Pacific the temperature is 29, add one degree and it becomes 30 degrees — at 30 degrees the evaporation is a lot bigger than if it were 23."

So the eastern side of the Pacific is warming at a faster pace because it was colder to start with.


Dr Cai Wenju is a senior principal research scientist at CSIRO's Wealth from Oceans Flagship and leads research that is using climate change predictions to maximise agricultural, urban and ecological water use opportunities. He was interviewed by Kylie Andrews.

http://www.abc.net.au/

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Oh my golly! El Niño misutoy...

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