Guest Post by Willis Eschenbach

There’s a new entry in the competition for the top spot in the “Climate Change Ruins Everything” competition. This is the claim that “Severe climate events could cause shortages in the global beer supply”, as discussed here on WUWT.

YIKES! If true, that is more serious than sea level rise … they explain the danger as follows:

The study warns that increasingly widespread and severe drought and heat may cause substantial decreases in barley yields worldwide, affecting the supply used to make beer, and ultimately resulting in “dramatic” falls in beer consumption and rises in beer prices.

So I figured that I should take a look at “barley yields worldwide”. I mean, if increasing heat causes “substantial decreases” in barley yields, we should see it in the record.

I went to one of my favorite datasets, the FAOSTAT database maintained by the Food and Agricultural Organization. It has production, yield, and area harvested for most crops since 1961. Here is their record of the barley yield over that period.

Since the global average temperature has increased over the period, I gotta say that it hasn’t had any visible effect on the global barley yield.

Is there a correlation between global barley yield and global temperature? To check that, I detrended both datasets to remove the long-term trend. This revealed that there is no statistically significant relationship between global temperature and global barley yield (p-value = 0.16).

However, I figured that this lack of correlation might be a result of the fact that I’m looking at the whole globe. So I repeated the analysis using the temperature and yield data for just the United States. In this case, it turns out that in the US there is indeed a negative correlation between temperature and barley yield. For every degree of US warming, the US barley yield drops by 2.7 kg per hectare (p-value = 0.01).

So it seems that they are right—barley yield does in fact go down with increasing temperature.

But how much difference does this make in practice?

To see that, I calculated just how much difference the change in US temperature made in the US barley yield. It turns out that the temperature rise in the US since 1961 decreased the US barley yield in 2012 (last year of the Berkeley Earth temperature data) by about 4.7 kg per hectare … and since the 2012 US barley yield was 6,251 kg/hectare, the warming in the US reduced the barley yield by about six-hundredths of one percent.

My term for that kind of result is that it is a “difference that makes no difference”.

In other words … the great beer panic of 2018 is just another in the long line of the alarmist “sky is falling” scare stories about the eeevil effects of “climate change”. So if you are of a mind, you are welcome to drink some beer to celebrate the good news … we’re not gonna run out.

My very best to you all,

w.

PS—When you comment, please quote the exact words that you are referring to so that we can all understand just what you are discussing.