Of rapid desertification and greening

Collage of two images from promotional video of EWF

In a previous post I was puzzled why a journalist blamed “climate change” as the cause of “rapid” desertification, while the region is greening for at least two decades. To recapitulate, in the evening news there was the story of a company that plants trees in Burkina Faso in order to fight against desertification and give more resources to the people living there (like make products that can be sold at the local market). As I said then, I have nothing against that. On the contrary, I applaud such an effort.

I did have a problem with the statement from the reporter that “because of climate change, the Sahara is dangerously advancing in the Sahel region, also in Burkina Faso”. This was a strange statement knowing that the area of the Sahel, in which Burkina Faso is situated, is “greening” in the last decades. It is probably a cycle that is repeating itself for many centuries or even millenia. In the 1970s – 1980s there were severe droughts, which were followed by a period with more rains and subsequently more vegetation. In such a light, a statement that the desert is dangerously advancing is puzzling to say the least. My initial guess was that the reporter didn’t know about that cycle and didn’t investigate it further.

In the meanwhile I found out that this statement was not from the rich imagination of the journalist, but actually came from the company itself. They made a promotional video in which they made similar statements. Looking at the video it seems the journalist was supplied with a frame work and could even use some stills from the video to make his report more entertaining. Both benefit: the company had free publicity in prime time, the journalist an easy report with lots of drama.

The video starts with a desolate flute melody and this introduction:

We all know that the desert grows in Africa. And that the people and animals must struggle every day to survive in the Sahel. Through climate change, forests disappear and fertile soils dry out.

Advertisement

Climate begins at the 1950s

When someone would ask “Are heatwaves increasing?”, what would you answer? Probably something like “That’s common knowledge, we all know that!”. Sure, but why? “We hear it everywhere”.

I heard it many times before and had no doubt it was true. At first glance it seems straight forward and logical. When temperatures go up (global warming, you know), the frequency of extreme temperatures go up. It has been told that the frequency of heatwaves is unprecedented and even ramping up in the last years.

I hear around me that we now live in a more extreme world. In stead of just believing this story line, I wanted to see for myself. I came to realize that this data exist. We call extremes in temperatures “heatwaves” and “coldwaves”. Okay, heatwaves increase, but the problem started when I asked myself: “How much?”. The answer was not exactly what I expected it to be…

First things first: looking for the dataset. The Belgian dataset seemed to be very hard to find and was really confusing. I found bits and pieces of it and nothing seem to match. I found that their definition of “heatwave” changed over time. That could well be the reason for these bits and pieces. The Belgian temperature dataset was not freely available either, so reconstructing it would not be possible. This wasn’t going to be easy.

But our neighbors in the North kept their records as well and, more important, they share their data with the world. It was very easy to find the list of heatwaves in De Bilt from 1900. It is not exactly what I searching for, but the situation from the Netherlands should be relatively similar. De Bilt is only a couple 100 km from Brussels. With the same definition, there will be probably somewhat more heatwaves recorded in Brussels (it is more to the South), but considering that in the average in the GISS dataset are made with stations until 1,200 km from each other, this should not be a problem.

This is what the Dutch call a heatwave (it is the current Belgian definition also):

A heatwave is a succession of minimum five summer days (maximum temperature of 25.0 °C or higher) from which minimum three tropical days (maximum temperature of 30.0 °C or higher).

I thought the heatwave data would represent extremes well. It is the threshold above which temperatures are recorded, so only the extremes are visible. The more data comes above this threshold, the more extreme the temperatures.

So I fired up Calc and loaded the KNMI data in a spreadsheet. Then I plotted it as a graph. The result was surprising. I expected, well, a steadily increase. Maybe not as steep as people suppose it is, but yet increasing. But that is not really what I saw.

Heatwaves De Bilt 1900 until 2013

It looks more like a cyclical event in which temperatures didn’t get above the threshold before 1911 and also between 1951 and 1975 (smack in the middle of the period of the rise and fall of the ice age scare).

Also, our well feared heatwaves in the 1990s and 2000s seem to be very bleak against the 1940s. I knew that the 1930s-1940s were warmer globally, but I didn’t expect to see it that clearly in the data closer to home.

The heatwave data consists of summer days (maximum temperature ≥ 25.0) and tropical days (≥ 30.0 °C or higher). The ratio between the two are about the same. One would expect with “global warming” that the tropical days increase against the summer days. It isn’t.

But, but, why do those people say that there are more heatwaves than before? Do they use other data? No, just look at just a very small selection of quotes about more heatwaves than before.

One from Belgium (translated from Dutch):

[…] Between 1981 and 2010, 10 percent of the world’s surface had to deal with extreme heat waves. That is 50 to 100 times more than the 0.1 to 0.2 percent during the period from 1951 to 1980. […]

One from The Netherlands (translated from Dutch):

[…] There were more heat waves in the last thirty years than in the fifties, sixties and seventies of the last century. […]

Not only in our little country, but also from the States:

[…] A new study examining six decades of global temperature data concludes that a sharp increase in the frequency of extremely hot summers can only be the result of human-caused global warming. […]

See a pattern emerging? They all talk about the last 60 years, the period from the 1950s, etcetera. They seem to forget there was life before 1950. If you take this period, where does that takes us in the graph? Let’s look at what they compare with:

Heatwaves De Bilt 1951 until 2013

This makes some things clear. The different time frame gives the (false) impression that:

• this warming is unprecedented (it isn’t, there was a period with similar or even more heatwaves in the past, but when one only looks from the 1950s this could not be seen)
• the intensity increased in the late 1990s till the half of 2000s (it did, but this happened before).
• there were no heatwaves at the beginning of this period and then from the 1970s heatwaves start popping up (that’s true, but there was a period with a similar, even hotter temperatures, before the 1950s)
• heatwaves are ever increasing since the 1970s (if you don’t look at the period before 1950 it is, otherwise it isn’t)
• in 2006 the intensity increased from 1 to 2, the speed is increasing! (it was increasing, certainly when one saw this in 2006-2007, but there were identical or even bigger increases in the past).

This seems not to be much different than many things in climate communication: there is a core of truth in it, but it lacks balance. Although it is an excellent opportunity for those who want to dig into it (I learned a thing or two about climate/weather by figuring things out after being surprised by some claims), for the public this is misleading. If one only look at the data from the 1950s on, there is a reason for alarm. But that scare has more to do with a lack of perspective.

What about cycles?

In previous post I concluded with the remark that probability theories are not falsifiable in a strict true|false way, but they can be seen as competing theories that can be compared. The theory that makes the clearest predictions of future outcome and that describes best previous and current observations, will be more preferable. Maybe this was a bit an abrupt ending, so I will explain a bit more in this post. Especially the Global Warming theory against one competing theory: the Natural Cycle theory.

First, let’s look at some long term measurements of temperatures. Below the Giss dataset, starting from 1880 (figure 1).

Figure 1: Giss Global Mean Land-Ocean Temperature index, March 2013 | Source: http://data.giss.nasa.gov/gistemp/graphs_v3/

I will accentuate some trends on this graph to explore the two theories. The lines were made with a simple graphic editor, so they don’t pretend high accuracy. They are drawn to give some indication of trends or, more accurate, how trends are perceived.

The global warming theory

The Global Warming Theory claims that we put ever increasing amounts of CO₂ from burning fossil fuel in the atmosphere. CO₂, being a greenhouse gas is the major driver for the temperature increase. It is a plausible theory and can explain a lot. At first glance one could easily deduce that man and industrialization has caused global warming (figure 2). It explains the increase of temperatures, especially the warming at the end of the 20th century (which is perfectly in line with the CO₂ increase at that time).

Figure 2: Representing Global Warming

But it doesn’t explain very well the warming in the first half of the 20th century. There was not much CO₂ added in the atmosphere yet (CO₂ started to pick up speed in the second half of the century), so this warming supposed to be of natural cause. But after this the temperature was decreasing or stayed the same when more CO₂ was “spewed” in the atmosphere. Compared the warming of the first half to the warming of the second, which has the same increase (figure 3), but this time it is supposed to be primarily of anthropogenic cause.

Figure 3: Parallel warming begin and end 20th century

It also doesn’t explain very well the stagnation of the last 10+ years in which there was more CO₂ in the atmosphere than ever before. If CO₂ is the major driver of the temperature increase this stagnation doesn’t fit very well. In that case one would expect there is a driver (or a set of drivers) that is as strong as CO₂.

The natural cycles theory

The Natural Cycle theory claims that the earth is warming and cooling in cycles. There are cycles of about 30 years, but there are also other cycles that are longer, like 300-500 years. The last one was called Little Ice Age (of about 500 years) and followed the Medieval Warm period (of about 400 years).

Figure 4: Representing Cycles

When one looks at the graph from 1880, the temperature doesn’t increases gradually, but one can see regular shifts in which there are increases followed by decreases or stagnations (figure 4). It explains the cooling until the 1910s, the next 30 years a warming, the next 30 years a small decrease/stagnation, the next 30 years a warming. Next, according to the theory the current stagnation should not be a surprise at all and even could last for some decades.

More questions

But doesn’t CO₂ has an effect then? Of course it does. As a greenhouse gas, everything else being equal, it will give some warming if there is more of it. But it is not necessarily the major driver as assumed in the Global Warming theory.

But doesn’t the graph show a large upward trend? The upward parts are way larger than the downward/stagnation parts. True, but this probably has more to do with the scale of the Y-axis. Expand the scale and warming will seem to go trough the roof. Compress it and the warming will seem unimpressive.

But what about the increase itself? According to the graph there is an temperature increase of about 0.8 °C over the last 130 years. Isn’t that reflecting the industrialization of our society? Could well be, but we came out of a cold period around 1850 (end of the Little Ice Age). If the last large (cold) cycle was about 500 years in length, then a 130 year of warming shouldn’t be that unusual…

To end

Of course this doesn’t prove anything. But it gives an indication that the recorded warming can be explained otherwise or, well, let’s say is also “consistent with” other theories. The global warming theory is not the only theory that can explain the temperature increase in the last 130 years. It shows that there is at least one other competing theory that is plausible and can be used to compare.