It’s been a hard week for gardeners. El Niño is kicking up his heels in the Pacific, developing from warm ocean water in the central and east-central waters of the Pacific and drying out some areas of the Guanacaste Province.

The news outlet AM Costa Rica reported this week that the National Emergency Commission (CNE) issued yellow, orange, and red alerts across parts of the country ahead of expected drought conditions during the upcoming dry season.

The El Niño phase of the Southern Oscillation cycles about every four years, but cycles of two to seven years have been demonstrated. The second part of the phase, known as the ENSO (El Niño/La Niña)-Southern Oscillation, is La Niña. La Niña is the cool phase of ENSO.

While El Niño brings high air pressure in the west and low in the east Pacific La Niña reverses the cycle with high pressure in the east Pacific and low in the western Pacific. Both phases of the ENSO cause changes in local weather.

Although some reports will talk about a change in climate caused by ENSO, this is a misconception. The results of ENSO are a normal and natural change that has been present, in all probability, for thousands of years, perhaps even millions of years.

There is, however, an interesting ‘second piece of the puzzle’ that helps explain why there are some years when the ENSO’s effects are horrific and other years barely noticeable. It is the Atlantic Multidecadal Oscillation (AMO). Never heard of it? Not surprising.

The AMO is a cycle that affects the surface temperature of the waters in the North Atlantic. It is connected to shifts in hurricane activity and intensity and patterns and intensity of rainfall.

Most of the models for the AMO have been directed at weather patterns in the northern hemisphere, including severe drought in the U.S. Midwest that effects grain production and patterns of rain and snow in Western Europe although there has been mention of its effect on parts of Brazil and Africa.

While the ENSO period is fairly predictable, the AMO cycle is not completely understood or predictable, as its period of oscillation is longer than that of ENSO.

What does that have to do with gardening?

Well, ENSO and AMO are mutually interactive and influential. This explains why we can go through an El Niño or La Niña phase here in Costa Rica with little change in the local weather in Guanacaste while we get higher than average rainfall – some of it catastrophic – on the Caribbean Coast.

We can’t rely on the idea that ENSO is our sole gardening predictor, and so far as I have found, there is little information on how the AMO, which, as its name suggests, is cycling in multiple decades, and the ENSO mix to give us some prediction of what our weather will be in local areas of Costa Rica.

So, when you are planting, keep in mind that the El Niño effect you are relying on for rain or sun may just be in league with the Atlantic oscillation.