El Nino is back. What does it mean?

El Nino is the name given to the natural cycle that involves the eastern Pacific getting warmer in the area close to the equator. (La Nina is the name for the alternative cycle when the waters there are cooler. The two together are known as the El Nino Southern Oscillation – ENSO.) This is one of the most significant natural cycles and occurs every few years. It has the potential to change weather around the world. Take a look at this graphic showing the sea surface temperature anomaly. The darker the red, the warmer it is relative to the long-term average.

Source: Climate Reanalyzer

You can clearly see how the water temperature off western South America is warmer than usual, which is the classic definition of El Nino. The name comes from how local fishermen noticed the change  in the water and how it seemed to always arrive in the late fall – about Christmas time. El Nino means ‘the boy’ and refers to the Christ child of Christmas. The name has stuck.

But, the important thing is to notice how the warm water stretches all the way across the Pacific Ocean. The significance of this lies in the fact that warm water creates atmospheric low-pressure areas which results in thunderstorms. There is now a Pacific Ocean-wide corridor of low pressure which will allow thunderstorms to develop and travel all the way from Asia to South America. One of the things this leads to is a change in the Hadley Cells.

Hadley Cells are circulation patterns in the atmosphere. Warm air near the equator rises and then travels towards the poles at high altitude. When the air reaches the mid-latitudes it sinks back to the surface and travels back towards the equator. This circulates heat and causes the trade winds. A stronger El Nino results in stronger Hadley Cells. Live Science has a nice graphic here showing how this all works.

You can probably see where this is going. More heat is being circulated through-out the world as a result of El Nino. Changes in the heat and water vapor input in a given region will result in changes to the weather in that region. How much of a change and what kind can be expected? That is a big variable. Some regions will experience greater rainfall. Others will experience droughts. Depending on the strength of the El Nino event, the effect could be anywhere from very mild to catastrophic.

Some of the most dramatic example of El Nino effects is a series of famines that have occurred in what is modern-day India, including the Great Famine of 1876-1878 (5.5 estimated dead) and the Bengal Famine of 1770 (10 million estimated dead). These famines occurred when the monsoons did not occur and the crops failed. The famines were greatly aggravated by British mismanagement.

What has been found is that severe droughts in India always occur during El Ninos, but not every El Nino leads to droughts in India. The apparent link seems to be where the Pacific is warmest. When it is warmer in the Central Pacific, India has droughts. When it is warmest in the Eastern Pacific, India is spared. Take a look at the plot of surface temperatures, similar to the plot above.

Source: Climate Reanalyzer

The figure above showed the difference from the average. This plot shows the actual average temperature. The way I interpret this data is that it is warmer in the Central Pacific region than in the Eastern Pacific region off of South America. This could be bad news for India. The good news is that Britain is not handling the management any more.

But, El Ninos are not bad news for everyone. Actually, for us in the U.S. it will be a good thing. A typical El Nino brings mild temperatures and more rainfall for the southern half of the country. This would be particularly welcome in the mid-Plains and the Southwest where drought has been raging for many years. In fact, several states out here are at risk of running out of water.  More rain would be good.

So, let’s talk about the White Elephant sitting in the middle of the room. Is global warming affecting the ENSO cycle? Quite simply, we don’t know yet. There are some that believe a connection exists, but more data is needed. What is known for sure though, is the El Nino affects the short-term accuracy of our computer models. The models are highly accurate when predictable conditions exist. But, unpredictable events like ENSO and volcanic eruptions disrupt them. The good news is that when the events occur and are included in the models, the models once again become highly accurate – in excess of 95% accurate and getting better. I have not heard what the models are forecasting with the this current El Nino included, but I will keep a look out for any news.

What about that expanded harvest?

So, to recap, deniers first said there was no global warming. Then, they said any warming was so small that we didn’t need to worry about it. Then, they said it was all just a natural cycle. Now, they are saying it is actually good for us. Do you see a trend here?

One of the things they are now claiming is that global warming will increase the zone where we can grow crops and increase the length of the growing season. In this way, it is actually  good for us. So, how is this turning out?

I have always been very skeptical of this claim, mainly because I grew up in agricultural areas and have always followed agriculture. I do some work in the local vineyards with some friends in this area. Growing a crop is about a lot more than planting seeds and then kicking back until harvest time. You have to worry about weeds, disease, insects, watering and weather – just to name a few things.

Droughts and heat waves have a devastating effect on crops. Just take a look at what is happening to the farms in California right now. They are having to plow their crops under because they don’t have enough water. On the other hand, too much water can be just as bad. A flooding rain can wash a whole farm out in a matter of a few hours. The evidence shows that overall, droughts and floods have been about the same so far, but dry areas are getting drier and wet areas are getting wetter. So, areas with droughts are getting worse and areas with floods are also getting worse.

Another weather event that farmers fear is the hail storm. A severe hail storm can pound a crop into the dirt in just minutes.

Of course, the obvious point is it doesn’t matter how long the growing season is if you don’t have a crop.

And, a warmer climate will also result in better conditions for insects and diseases that destroy crops.

None of this takes into account the fact that grain crops such as corn and wheat are very sensitive to heat. The yield goes down once the temperature gets higher than a certain point.

I had all of this in mind when I read an article in the May 13 issue of Eos, Transactions, American Geophysical UnionClimate change, water rights, and agriculture: A case study in Idaho reports on an investigation into the effects of climate change on agriculture. Their findings?

“They found that if climate change increases the volatility of the temperature and the water supply, irrigated agriculture in the region could face significant damages. In fact, crop revenue losses could be up to 32%.”

This is just one study for one particular region, but the point is pretty clear. Just because more land is available for growing crops and the length of the growing season is longer, it doesn’t mean there will be a larger harvest. Climate change will make certain things better for crops, but it will also make a lot of things worse at the same time.

Again, we see that all of us at the bottom will have to foot the bill for all of this. This time, in the form of higher food prices.