We are leaving for Aruba Saturday morning. Having been there several times in the past, and having good weather always, I wanted to know if El Niño is having any effect on the weather in Aruba.

Dave Seltzer
Cincinnati, OH

Well, since it's past Saturday morning, you probably know better than I that Aruba is generally enjoying mild and sunny weather this winter, although there's been more rain than usual. Positioned as it is in the Caribbean, north of Venezuela, Aruba is sheltered from El Niño's most direct effects by the mountains and landmass of northern South America. By the time El Niño's warm, moist air makes it over this land, the moisture has mostly been wrung from it. Aruba and the Caribbean in general are seeing more diversity in the weather than normal, but not enough to ruin most people's vacations.

How long does El Niño last, and how will it affect us down here in Yuma, Arizona?

Angel Perez
Yuma, AZ

Down there in Yuma, Arizona, you're probably already realizing that El Niño can mean more rain than normal in both the fall and the winter. In fact, this past September, the pacific hurricane Nora (fed by El Niño's energy) chewed its way across Mexico and landed in Arizona, dumping a LOT of water. That almost never happens, except in a strong El Niño year.

Not far from you, scientists have taken tree ring samples that show El Niño has visited Arizona many times in the past. The rain and snow it brings is recorded in thicker tree rings than normal. Look at our section on El Niño's Reach Through Time for more about this.

As for your question about how long El Niño lasts: that's kind of a trick question. We tend to think of El Niño only as something that makes bad weather for half a year, and then goes away. But that's like saying Halley's Comet exists only when we can see it, once every 76 years. Even when we can't see it, Halley's Comet is still out there in space, tracing the same orbit that it has for thousands of years. El Niño is the same way. Every few years, we see it in one extreme of its cycle. But even when it seems to go away, it's still out there, hidden in the water of the Pacific ocean and the air above it, a mysterious rhythm of the sea and the wind that only makes itself known every few years.

This time around, we can expect El Niño to continue upsetting the weather for another few months, as it has since last summer.

Is El Niño likely to have an effect on the growing season in the central US?

(name witheld by request)

Anything that changes the weather patterns over such a large area as El Niño does, will have some effects. In the central US, El Niño has meant a milder winter than normal in the north, and crops like winter wheat are going to do well. In the southern central US, it's been a lot wetter than usual. It remains to be seen if this will increase the chance of flooding later, but it probably will mean an early and healthy start for spring crops. I'd say farmers in Kansas City, and in the rest of the Great Plains and the Midwest, will generally be pleased with El Niño this year.

There is some scientific speculation that part of El Niño's aftermath will be a hot, dry summer in North America. This is not an official scientific prediction, so I wouldn't get too worried yet. We just don't know enough yet to make that kind of prediction with any useful level of certainty. But there are hints in records of the past that we shouldn't be too surprised if this happens. Watch the dispatches section for a guest dispatch next week from meteorologist Peter Chaston on just this topic.

I would like to receive statistics on the effects of El Niño in first, second and third world countries, compared to its effects in the US.
Thank you,

Stephon Barnes
Philadelphia, PA

I should point out that the first, second, and third worlds are mostly political, rather than geographic, distinctions. Therefore, it's probably more useful to think of geographic regions, like South America or Africa or Southeast Asia. You can take a quick look at El Niño's Reach to get an idea of how El Niño changes weather in different parts of the world.

El Niño respects no national boundaries. Even different parts of the same country may feel very different effects from El Niño. In the US, Florida, the gulf states, and the west coast get a lot more rain than usual, while the Midwest gets a break from the usual cold winter. El Niño seems to get its fingers into most parts of the world, one way or another.

What is the prediction for the monsoon rains for the southern part of India during 1998?

Nagendra
Bangalore, Karnataka, India

Southern India is in a zone of relative unpredictability for the effects of El Niño. That's another way of saying that something abnormal will probably happen, but no one can say exactly what. Last summer and fall, southern India experienced delayed monsoon rains that eventually became more normal. The outlook for 1998 is for more normal conditions, but that's really an educated guess. If you look at historical records (as Gilbert Walker did in the early 1900s - see El Niño's Reach Through Time) you'll see that in your part of the world, in El Niño years, summers are usually drier than normal, and the onset of the monsoons can be delayed.

If you want more detail, the International Research Institute for Climate Prediction has compiled a lot of historical records for specific regions and countries. is the summary for India.

Will El Niño continue to influence the weather in 1999 and if so, will it be a warm or cold June and July?

(name witheld by request)

That's a great question, because it helps us think of El Niño not as an isolated event, but as a pendulum that swings first in one direction, then back in the other. In 1999, it won't be El Niño that affects us, but La Niña, its alter-ego that represents the pendulum swinging back, as the cycle plays out. There is some evidence, but not nearly enough to say with certainty, that a La Niña summer here in North America is likely to be hotter and drier than normal, and the winter to be colder.

One thing is certain, though: the cycle of El Niño and La Niña will continue to operate, and anywhere from two to ten years (most likely two to four years) from now, we will see El Niño again. The hidden mechanism out there in the Pacific ocean and the atmosphere above it never stops.

Does the "Greenhouse Effect" have anything to do with this, and if so, are there any long-term effects for the environment? If in the future there are many consecutive El Niños, is there a possibility for the polar ice caps to partially melt?

Dallas
Buffalo, NY

Your question belongs under the "let's open a can of worms and pour Tabasco sauce on them" heading. There's a lot of debate about global warming, and some of it is pretty heated, because there are a lot of economic costs involved with changing our dependence on fossil fuels, and stopping deforestation, just to mention two of the many proposed causes of warming. Of course, there are a lot of economic costs to having the ice caps melt and all our coastal cities flooded, too! And that's just for starters.

The philosopher Bertrand Russell said that the more heated and angry an argument is, the less likely it is driven by facts. No one has heated arguments about whether or not the sun will rise tomorrow. But if you apply Russell's adage to global warming, it seems that we still have a lot to learn.

George Philander of Princeton University put it to me this way: say you are in a canoe going down a river. You know that somewhere ahead is a waterfall, but you don't know where. You want to ride that canoe as far as you can, because you don't want to have to get out and walk. The river looks calm now, so you keep going. Question: when do you get out?

We're like the canoeist. Virtually everyone agrees that the Earth's climate is warming. For example, globally, 1997 was the warmest year ever recorded. But there is little agreement about how much our climate has warmed, and how much more it will warm in years to come. Humans have probably contributed to the warming, but again no one knows how much. If current trends continue, then the Earth's climate will undergo some pretty dramatic changes, even in our lifetimes. This could create a *lot* of problems. Like the canoeist, we haven't seen the waterfall, so we don't know how bad it is, or where it is. But most scientists now agree there is a waterfall ahead of us. Will we pull over to the banks in time?

El Niño is part of the Earth's weather systems, so it's not appropriate to talk about the Greenhouse Effect's influence on El Niño without talking about its influence on climate in general. And even though 1997 was a very warm year, and the current El Niño is one of the strongest ever recorded, Antarctica had an extremely *cold* winter in 1997, possibly due to El Niño. So it's a very complicated matter...El Niño will not melt the icecaps, it's the total heat content of the oceans and atmosphere (or "global temperature") that will do it, if it should happen. If you throw a baseball through your neighbor's window, will the baseball be blamed? How about your hand? No, it's you who is to blame. El Niño is climate's hand, so to speak.

If you'd like to read further about this topic, check out the book "The Next One Hundred Years," listed in our Resources section. It's superb.

What data do scientists use to predict that an El Niña might follow the current El Niño?

Bob Gorsuch
Auburn, WA

Good question, but let me be picky for a moment. It's actually La Niña, not El Niña. In Spanish, La refers to female, and El to male. So what's this female/male stuff all about?

As we point out in Anatomy of El Niño, Peruvian fishermen gave El Niño its name about a hundred years ago. It means "the (boy) Child," which is short for the Christ Child, because in years when El Niño came, it seemed to show up around Christmas.

We now know that El Niño is one extreme of a cycle that takes from two to ten years to complete. Scientists officially call this cycle ENSO, short for El Niño Southern Oscillation, and unofficially call El Niño's opposite extreme La Niña, "the (girl) Child." As El Niño starts to go away, La Niña starts to arise, like two kids on a teeter-totter. (Talk about a couple of spoiled brats!) Roughly speaking, La Niña does in the western Pacific what El Niño does in the eastern Pacific. Therefore, if we see a La Niña form this summer, it will probably get wetter in the west, near Indonesia and Southeast Asia, and drier in the east, along South America, and maybe even in North America.

Scientists have good weather records available from the past century, and then some. Generally, the prediction that La Niña will follow El Niño is based on what's happened in the past. This leads to a probabilistic form of prediction, something like "well, in seven out of the last eight times El Niño appeared, La Niña effects showed up in the following year - therefore, there's roughly an 85% chance that we'll see La Niña this year." Scientists are trying to supplement this by making computer simulations of climate (they call them numerical models), which combine past data and current observations to make a forecast.

It seems like spring is coming earlier and earlier to Seattle and the northwest—is this really happening? Are we predicted to have a dry summer?

Patty Lyman
Seattle, WA

Let me ask you a question first. If you were at the coffee shop, and the next person to walk in the door was six feet six, would it seem that all the customers are getting taller these days? Probably not. How about if the next ten people were over six and a half feet tall? Well, maybe, unless the basketball team had just decided it needed a cappuccino break.

Scientists avoid trying to draw large conclusions from small amounts of data. That's part of the problem with climate prediction in general, and El Niño prediction in particular: in many cases there's not enough data to make reliable estimates of what might happen. You might have to count a hundred or more customers to get an idea of average height, and you might have to look at a hundred El Niños, or a hundred springtimes, to get a better understanding of the probability of different effects occurring.

In other cases, no matter how much data we have, the best we can ever do is say there are several possible outcomes, and assign rough probabilities to them. That's part of the nature of some inherently unpredictable systems - the best we can ever do is talk in generalities. The current term for these systems is "chaotic" and it means that no matter how much data you collect about the workings of some systems, you'll never be able to predict what they'll eventually do, only what they'll probably do in general, and who knows when!

I don't want to get into it too much here, but the world is filled with such chaotic systems, where making tiny changes in the starting conditions can lead to huge and unpredictable differences in the outcome. A fresh branch of mathematics, called Chaos Theory, has arisen in the last thirty years to describe these systems. The original idea came from a meteorologist (appropriately enough) at MIT named Ed Lorenz, who was trying to figure out how to use a computer to predict the weather for more than a few days. They're still working on that one.

So, the answer to your question depends on trying to figure what an inherently unpredictable system is likely to do. Spring may seem to come earlier lately, but only thirty years ago, most scientists felt that we were on the verge of entering a new ice age. Times change. It may be that the warming trends that have become more pronounced in the 1980s and 1990s are a blip in climate, a random aberration like having the basketball team walk through the door, and that soon it will be business as usual. Or it may be that global warming trends are starting to take hold, and soon you'll be planting zinnias in Seattle on March 1...

As for your question about this year, some evidence from the past suggests 1998 will be a drier summer in your region, but don't hold your breath. One thing is certain, though: anyone who tells you they know for sure is a charlatan.