It would be easy to predict the current El Nino, which by most accounts is gaining strength, would lead to a wet winter in the southern half of the U.S. and drought and reduced cotton, corn and rice crops in South Africa and Asia in 2015 and early 2016.
But nothing is that simple, according to two USDA Office of the Chief Economist meteorologists who gave presentations during the University of Arkansas’ Food & Agribusiness Webinar on the “Global Impacts of El Nino on Agriculture on Tuesday (July 28).
“I’ve seen a lot of press reports talking about this year’s El Nino, saying that it’s going to be one of the strongest on record,” said Mark Brusberg, deputy chief meteorologist with the Office of the Chief Economist at USDA who spoke along with Brian Morris, senior meteorologist with the OCE from Washington.
“Basically, what the Climate Prediction Center and other agencies are saying is that, in the three-month period of February, March and April of 2016, there’s still an 80 percent chance that there’s going to be an El Nino. So not only are we looking at a strong event, but it looks like it’s going to last well through the end of this calendar year and into 2016.”
The El Nino weather phenomenon describes the conditions that develop when the water around the Equator in the Pacific Ocean off the coast of South America becomes warmer than normal. La Nina describes conditions when the water becomes cooler than normal.
“El Nino is the name given to the warm water that, at the turn of the 20th century, fishermen described off the coast of the Pacific. We got the name because it occurred around Christmas -- the Christ child,” said Brusberg. “At the same time, in other parts of the world, people who monitor the weather were seeing there were other impacts at the same time.
Australia, India impact?
Among those were droughts in Australia and India.
There’s nothing unusual about the El Nino Southern Oscillation or ENSO, as it’s sometimes called. “It’s a naturally occurring cycle that happens every three to seven years,” he said. “When we look at the actual temperatures recorded in one of the zones in the Pacific we monitor , we see almost as many recordings above normal that are below normal.
“Going back from 1950 to about 2013 or so, we had 190 monthly observations above normal and about 178 below normal so that’s pretty close. And you can see from the chart it goes up and down and up and down.”
The 30-year running average compiled by meteorologists is adjusted for global warming to reflect the fact surface temperatures have warmed about a half of a degree over the last 50 to 60 years.
“If anyone was watching the weather back when the Peruvian fishermen first discovered this, they would have noticed you had stormier conditions prevalent in the central and eastern Pacific,” said Brusberg. “When you have warm water in the eastern part of the Pacific, it weakens the winds, and you tend to have higher pressure over Australia and lower pressure over Tahiti.”
Simply stated, that means you would tend to have dryer weather in places like Australia and southern Africa and wetter conditions in parts of the U.S. because the phenomenon tends to have an impact in other parts of the globe.
Warmer all the way across
This year the Pacific is warmer all the way across the Equator, said Brusberg, as he displayed a slide depicting the temperature rises of recent months. (The temperatures are recorded using a network of floating buoys called the Argo system. The buoys can be made to sink hundreds of feet into the ocean and record temperatures at those depths before they pop back to the surface.)
“Over the last month we have anomalies as much as 3 degrees centigrade above normal off the Coast of South America, and in the heart of the Pacific, it’s anywhere from a degree and a half to two and a half degrees above normal,” says Brusberg.
“This has been going on for several months now, so we have – I don’t want to say it’s a mature event, but it is getting stronger, and it’s getting older, and we’ve seen the coupling of the atmosphere for several months now.”
Brusberg, who specializes in countries in the Southern Hemisphere, says some of the droughts linked to the El Nino phenomenon have been significant, leading to reduced yields in the primary crops of the regions affected.
“I started covering South Africa around 1991, and I remember that drought very well,” he noted. “It was a very bad year. Now let’s look at the strength of the current El Nino.”
The question naturally arises about whether a stronger El Nino means the drought is going to be worse or that the flooding (in places like California potentially this winter) is going to be worse, he said.
Worst crop in weak El Nino
“You would think that, but if you look historically, that’s not always the case. In the 1997-98 year, which was very strong, you can see they (South Africa) did have a departure from normal. But then there was a weak El Nino, where they had a departure from normal, but it wasn’t nearly as much. In the last El Nino, 2009-10, they actually had above normal yields.
“In 2006, however, they probably had their worst crop going back to the 1990s, and they had one of their driest summers going back to 1983. It was also warmer than the other El Ninos. Yet this year was just barely classified as an El Nino.”
Similar situations have occurred with the wheat crop in Australia, which has been in a drought for several years, with farmers having good yields in some El Nino years and poor crops in other.
Argentina, meanwhile, tends to have near to above normal years in an El Nino, and Brazil seems to be little affected most years because of the frequent rains it receives during the rainy season.
USDA’s Brian Morris said forecasting what may happen in India and in Southeast Asia can be problematic. “ENSO has a muddled effect with India these days, but I want to just spend a couple minutes, talking about the monsoon in particular, because that's where the El Niño has its biggest effect.
“India has a very distinct rainy season and a very distinct dry season. During the dry season, the El Niño, obviously, doesn't have as much of an impact as it does during the rainy season when they do, arguably, 75 to 80 percent of their agriculture.”
The monsoon, which moves in a circulation pattern, brings in a lot of moisture in off the Arabian Sea to the southwest of India. “It starts circling around through the Bay of Bengal and kind of comes up into the northern sections of India.”
Low pressure area forms
That’s because, as India heats up, a low pressure system forms over the midland and the air circles around the low pressure area, bringing in the moisture. “And this is what your rainfall pattern looks like during the monsoon season June through September.”
The west/southwesterly winds just bring up into the Ghats (mountain range) and drop an enormous amount of rain on the windward side of the Ghats. They wrap back around and bring not as much rain to the western coast – the region where much of India’s cotton, rice, soybeans and groundnuts are grown.
“You can see when the monsoon starts in June, they get a fair amount of rainfall, but it picks up and they get most of their rainfall for the year in July with a secondary boost in August, and then it starts to dwindle down around September before it drops off pretty rapidly for the remainder of the calendar year,” Morris notes.
“Typically, you expect it to be dry in India during an El Niño year, and statistically that's usually what happens,” he said. “It's become a little bit more muddled, as I said before, because of how it affects India through when it develops, when the El Niño develops, its timing, its strength. All these things have factors into whether or not you're going to see what they refer to in India as the monsoon failure or whether or not you're going to get normal conditions.”
To watch Brusberg and Morris’ presentations, visit http://www.uaex.edu/farm-ranch/economics-marketing/food-agribusiness-webinars/posts/strengthening-el-nino-2.aspx.