If you're a person who lives anywhere near the Pacific Ocean, you've experienced the fun of El Niño. But even if you don't, you've heard of its effects.
What happens during El Niño?
During El Niño years, which strike during the northern winter and the southern summer, ocean surface temperatures in the Pacific Ocean, particularly along its tropical eastern edge, spike. This causes changes in regional precipitation: for the most part, in areas with warmer ocean, there are increases in rainfall. But in some areas the "heavier"-than-usual clouds drop precipitation more coastward than usual, resulting in less rainfall in more inland areas. Also in regional areas of cooler water (such as the western Pacific), cooler ocean surface temperatures correlate generally with less rainfall. El Niño also changes regional ocean productivity: upwelling of colder, more productive water off the Pacific coast of North/Central/South America is temporarily subsided, and both human fisheries and marine predators have to make do with less small fish to feed on. But western Pacific countries see a slight increase in ocean productivity.
Why has everyone heard of El Niño?
Because the Pacific Ocean comprises a fairly large amount of the Earth's surface, and because El Niño results in an overall rise in ocean surface temperatures, El Niño years show up as warm years on long-term analyses of global surface temperatures. The last "big" El Niño, 1997-1998, helped make 1998 the warmest year yet for global surface temperatures, and climate contrarians you might meet on Gawker network sites are making reference to that event when they say the Earth "stopped warming".
Is the upcoming winter/summer going to be an El Niño?
...probably? Throughout the last few weeks I've read more and more reports on Pacific Ocean temperatures that seem warmer than normal. Current forecasts are that from June forwards there's a greater-than-50% chance that El Niño is happening for 2014/2015. And current forecasts are basing this off a Pacific that is as warm as, or warmer than, it was in 1997.
So this next El Niño is going to be really hot?
That's what it looks like.
And so 2015 is going to be the warmest year on record?
That's what it looks like.
But global warming was made up by scientists so they could use government grants to buy Porsches!
I live in ____, what can I expect from El Niño?
That's a great question, which Eric Holthaus at Slate wrote a great write-up about. El Niño would result in a warmer winter for Green Bay Packers home games, so if you're in Wisconsin, you could be in luck. If you're in Indonesia, where the east->west transfer of heat generally results in cooler and drier, conditions, then you might not be, as wildfires become easier to start and less easy to control.
Can we stop El Niño?
Only by stopping ocean circulation or by removing the Pacific Ocean. I don't suggest doing either of those. Looking at paleoclimatic records, it does seem like El Niño events are weaker during glacial periods than during interglacial periods. Thankfully (?), human carbon emissions have interrupted a natural cooling cycle, so we are unlikely to see weaker El Niño events for somewhere between 35,000 to 150,000 years from now.
1. The next 12 months are likely to be an El Niño.
2. Because humans like burning fossil fuels, this El Niño is likely to be strong.
3. If you live near the western Pacific, expect cooler, drier conditions.
4. If you live near the eastern Pacific, expect wetter, warmer conditions.
5. If you'd prefer your descendents to not have super-strong El Niño events, tell your favourite companies to stop burning so many fossil fuels.