Advanced Warning – get shovels and sledges at the ready

The UK has been hit with the warning of heavy snowfall this winter. Fantastic fun for some, terrible trouble for others. Whatever it means for you, it means one thing for the Pacific Ocean – rising temperatures.

In my last post I mentioned how a small change in ocean temperatures can have a catastrophic effect on our planet, well, every two to seven years sea surface temperatures offshore of north-western South America increase above average. Often 2 to 3^oC higher than normal (Glantz, 2001)! This is what is known as El Niño (Spanish for “the boy”) and what we are currently experiencing. El Niño is one half of the El Niño-Southern Oscillation (ENSO) cycle. The opposite phase, when unusually cool waters occur, is called La Niña (Spanish for “the girl”). These have globally affecting weather and climate consequences. Effects of the El Niño are wide reaching and can often be felt around the globe for over a year (Lizumi et al, 2014). Past instances resulted in flooding in Peru & Bolivia and droughts in Indonesia & Australia (Nakagawa et al, 2010).

So what causes this Spanish boy to show himself?

Usually, strong winds blow from East to West along the equator. With this, about half a metre’s worth of water builds up in the Western Pacific. To replace the water that’s been lost the Eastern current pulls up cold water from deep below. Hence, temperatures are typically cooler in the Eastern Pacific as opposed to the Western. However, during an El Niño the winds weaken, and the circulation of water lessens. This results in the Eastern Pacific being warmer than usual. That isn’t the end of the story... warm waters result in weaker winds, weaker winds result in warmer waters, and so on. Like a hamster on a tread mill, round and round. This positive feedback loop is what makes the El Niño grow.

 

You may remember the last time the effects of El Niño were felt in the UK – the winter of 2009/10. I remember it well; the first winter away at university. Unfortunately the roads were piled high with snow and lessons were cancelled, so like any sensible fresher I spent the time participating in a week long snow ball fight. Productive. Well, prepare yourself now, because news reports are claiming this to be the worst El Niño in recorded history.

Photograph: Me on swing being pelted with snow, 2010

Some people are looking forward to this event for another reason, not just the possibility of a few days off of work. Kasha Patel at NASA's Goddard Space Flight Center states that “the 2015-16 El Niño event will be better observed from space than any previous El Niño” due to the fact that since the El Niño of 1997/98, (the strongest on record), NASA has launched 19 Earth-observing missions, all currently in orbit. Not only will the satellite data show us what is happening currently, but the mass of data recorded can be assimilated into current models to improve them. Models rely on data, the more available, the better likelihood of an accurate model. As well as the data itself the observations are sure to increase the understanding we have of El Niño’s. After all, a useful model cannot be built solely from data without any understanding of the processes in force.

 

If you’re a betting kind of person, bookies have updated their odds of having a White Christmas in various places around the UK and Ireland. Now, just don’t go blaming me if you don’t win. And if you do win...