Australian scientists officially declare the onset of a ‘substantial’ El Niño event in the tropical Pacific.
What is El Nino?
The Christ child they called it, the fishermen of Northern Peru, who noticed around Christmas-time in certain years, a warm counter current flowing from the north, extending far south, lasting for months. We now know it can increase the water temperature by between four and ten degrees Centigrade. This warming of the ocean devastated the fishermen’s livelihood because it drove away the anchovies, and other fish, in search of the colder waters in which they thrive, but it pleased the farmers, some of the time, because it rained in the deserts, allowed them to grow crops in normally barren land. But El Nino’s didn’t always benefit them. The Moche civilisation was destroyed in the late 6th century when, following thirty years of drought, a prolonged El Nino brought year after year of torrential rains that washed away their crops and buildings and eventually eroded their entire civilisation. They tried everything they could to placate the weather Gods. Hundreds of fractured skeletons were found pertaining to that period. Human sacrifices thrown desperately from cliffs.
El Nino has a lot of blood on his hands. We have attributed China’s Great Famine of 1877-8 to an El Nino event. Between nine and thirteen million people perished and seventy million were severely affected. It is a global phenomenon. At its peak, the warm pool of water can extend as far as one third of the way around the globe and cover an area one and a half times the size of the United States. It can bring rain where there is normally drought, and drought where there is normally rain.
How often does it happen?
On average every four years, a strong one every fifteen years. What we call a ‘mega-Nino’, like the one that destroyed the Moche, occurs every 400 years. But it’s not regular. A decade can go by with no Nino event, and then you could have four in as many years. Then there’s also something called La Nina, the pendulum swing that sometimes occurs after a Nino event, which brings cooler waters, and its own brand of devastation. La Nina in 1988 caused the northward displacement of the north pacific jet stream, which in turn displaced storm tracks into Canada, effectively stealing the storms that bring the USA much of its rainfall. By July of that year, 43% of contiguous USA was suffering from severe or extreme drought. It was like the years of the Great Dust Bowl. Grain growers lost more than 19 billion dollars and the world’s grain reserves were halved.’
What effect is global warming having on el Niño events?
El Niño events are getting more ferocious. In the twentieth Century, El Nino’s have been stronger than for the past 130,000 years. The last Mega-Nino occurred in 1997. It caused 22,000 deaths world-wide and cost $33 billion in flood and drought-related damage. No-one predicted it with any decent lead-time, nor did they predict how long it would stay, or how severe the consequences would be.
Who feels it first?
Peruvian fishermen on the north coast where Peru borders Ecuador are some of the first people to physically feel a Nino event. The seas warm, I’ve swum in them myself. They are so intoxicatingly warm, where they are normally quite cool and fresh, that all the local children pile in for hours and have to be dragged out at meal times. For the children, it’s very simple; the Nino has arrived, and they make the most of it before the rains come, as they will in a matter of weeks, a few months at the most
What actually happens to the seas when an El Nino comes?
In a typical year, in spring, you get strong winds blowing towards the equator, and these, plus something called the Coriolis effect – the tendency of winds and currents to veer to the right in the Northern Hemisphere and to the left in the Southern normally – join forces to push surface waters away from the coast. To fill their place, cold water rises in what’s called an upwelling, bringing a whole host of nutrients to the surface which attract fish. Big ones and little ones. But, during El Nino events, there is a relaxation of the winds, and you get things called Kelvin waves bringing warm water eastwards from the Western Pacific. That causes a downwelling of warm water to depths of three hundred feet or more, stopping the nutrients rising to the surface. During the 1997-1998 El Nino, tens of thousands of seals and sea lions starved to death as a result.
There was also widespread flooding of low lying coastal homes because when water warms it expands and the sea level rises. And the Kelvin waves can raise sea levels on the Peruvian Ecuadorian coast by as much as ten inches.