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Parts and whole – watts with that?

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Guest message from Willis Eschenbach

As in many of my travels in scientific landscapes, this one begins with “I was curious …”.

In this case, I wondered how well the temperature in Central England (“CET”) coincides with the temperature of the planet.

In part, I was curious because I kept reading that the Little Ice Age, which bottomed out around 1700 AD, was just a European phenomenon. I often wondered if only a part of the world could cool down just like in the Little Ice Age, without the rest of the world cooling down.

CET is one of the longest temperature records. This curious record is that it consists of a combination of temperature records of varying different stations in the common area of ​​Central England. It stretches from 1659 to the present. Here’s a more recent piece of the CET record (seasonality removed) and Berkeley’s global temperature record on Earth.

Figure 1. Monthly Central England Temperature (CET) and Global Berkeley Earth Temperature.

Hmmm … looking at that, there seems to be very little relationship between them. R ^ 2 (lower left corner) is a measure of the closeness of the relationship, ranging from R ^ 2 = 0 (no relationship) to R ^ 2 = 1 (complete agreement). Reflecting on the question, I realized that the problem is that in a short period of time, months or years, rather than decades or centuries, temperatures in a small area of ​​the planet, like Central England, change much more than the globe’s temperature.

So what I needed to do was adjust the short-term variance of the CET so that it matched the Berkeley record, leaving the long-term variations intact.

To do this, I first took low-flow CET data. This gave me Figure 2.

Figure 2. Full temperature record in Central England along with LOW smooth by CET. You can see the coldest part of the small ice age around 1700 AD.

I then subtracted the low smooth from recent CET data (from 1850 to the present to fit the Berkeley Earth data period). This left me with only short-term (months to years, not decades or centuries) variations in CET data.

I also did the same with Earth temperature data at Berkeley to determine short-term changes in that data.

After I had both sets of short-term variations, I adjusted the average size of the short-term CET variations to match the average size of the corresponding Berkeley Earth short-term variations. Finally, I added a smooth LOWESS appeal to restore the original CET data, but with much less short-term variations.

I then used a simple linear regression for the CET data to best match the Berkeley Earth data. Figure 3 shows this result.

Figure 3. Temperature in Central England, adjusted variance compared to global Berkeley temperature.

It was a big surprise for me, and such surprises make me do science. I did not expect that the temperature of a small part of England would coincide so well with world temperature. R ^ 2 is 0.67, which is much higher than the previous R ^ 2, equal to 0.7, shown in Figure 1. And since the Little Ice Age is clearly visible in the earlier part of the CET record shown in Figure 2, it greatly increases the chances that the Little Ice Age was a global phenomenon.

Now I’ve also heard the claim about U.S. temperature records that the U.S. occupies only ~ 2% of the world’s area, and so we shouldn’t expect this to be like a world record. So I used the same technique to compare the Berkeley Earth record in the US with the Berkeley Earth world record. Figure 4 shows the result:

Figure 4. US temperature, adjusted variance compared to global Berkeley temperature.

Now the US is much larger than Central England, and so, as might be expected, the deal with global temperature is even better than the CET. R ^ 2 is now up to 0.76. For the past 170 years, temperatures in the United States have been very close to what global temperatures have been doing. Who knew? Certainly not me.

Finally, I’m going to speak here and say that the Little Ice Age was most likely a global phenomenon.

And that was my scientific surprise for today … how was your day?

My best to all,

g.