Warming trends in England from 1659

by Lubos Motl

Source: courtesy of  The Reference Frame

Because the Hadley Center has released the final temperatures in Central England for 2009, I decided to calculate a few things. Although I have also played with the monthly data, this text will be purely about the 1659-2009 annual data. It’s 351 years in total.

The average of the 351 numbers is 9.217 °C. The Pythagorean average of the deviation of the annual data from this average is 0.659 °C. The global warming advocates like to emphasize the warming trend in the last 30 years. How does the warming trend in the last 30 years – and in all other 30-year periods since 1659 – look like in Central England?

Click to zoom in: the y-axis is the warming trend in °C per century, the x-axis is time from 1659-1688 to 1980-2009.

In the late 17th and early 18th century, there was clearly a much longer period when the 30-year trends were higher than the recent ones. There is nothing exceptional about the recent era. Because I don’t want to waste time with the creation of confusing descriptions of the x-axis, let me list the ten 30-year intervals with the fastest warming trends:

1691 – 1720, 5.039 °C/century
1978 – 2007, 5.038 °C/century
1977 – 2006, 4.95 °C/century
1690 – 1719, 4.754 °C/century
1979 – 2008, 4.705 °C/century
1688 – 1717, 4.7 °C/century
1692 – 1721, 4.642 °C/century
1694 – 1723, 4.524 °C/century
1689 – 1718, 4.446 °C/century
1687 – 1716, 4.333 °C/century

You see, the early 18th century actually wins: even when you calculate the trends over the “sufficient” 30 years, the trend was faster than it is in the most recent 30 years. By the way, the most recent 1980-2009 tri-decade didn’t get to the top 10 results at all; if you care, it was at the 13th place. 😉

You can also see that the local trends are substantially faster than the global trends: that’s because the global variations are reduced by the averaging over the globe. For the sake of completeness, these were the most intense 30-year cooling trends:

1727 – 1756, -3.962 °C/century
1863 – 1892, -3.956 °C/century
1729 – 1758, -3.723 °C/century
1728 – 1757, -3.719 °C/century
1726 – 1755, -3.649 °C/century
1862 – 1891, -3.413 °C/century
1666 – 1695, -3.315 °C/century
1730 – 1759, -3.203 °C/century
1861 – 1890, -3.021 °C/century
1865 – 1894, -2.952 °C/century

An obvious question is what happens if you consider 10-year, 15-year, or 50-year trends. With my Mathematica code, it’s easy to find: you just change one number. 😉 As you may expect, if you use the 10-year or 15-year trends, the current era won’t get anywhere close to the winners. For example, these are the 10-year trends:

There is nothing special whatsoever in the recent epoch. I won’t even try to show you the list of winners because the recent decades would obviously be somewhere in the middle. The fastest warming trend extracted from 1 decade is by +18.6 °C per century in 1694-1703; the fastest cooling trend was by -23.9 °C per century in 1733-1742.

Yes, these are huge numbers and they’re true. The superfast cooling is related to the excessively low temperatures recorded in England sometime in the early 1740s. Most people don’t understand the “random walk” character of the temperatures: the shorter periods you consider, the faster trends you obtain: the trends approximately scale like 1/sqrt(time) – and in this case, the records were scaling even faster than that, as 1/time. Of course, none of these trends can be extrapolated to a century.

At the beginning, I chose the 30-year trend because it really had the highest chance to produce a recent “man-made” signal. It didn’t. It’s much more hopeless if you consider e.g. the 50-year warming trends:

Again, the recent era on the right side of the picture has no chance to compete with the late 17th and early 18th century: the 1960-2009 period with the +2.65 °C per century ends up outside the top ten. The winner is 1688-1737 with the trend +3.83 °C per century. The fastest cooling was in 1722-1771, by -1.69 °C per century. These 50-year trends can’t quite be extrapolated to a century, either. But they’re much closer to that than the 10-year or 15-year trends.

Finally, our generation teamed up with our parents, grandparents, and great grandparents can marginally win if we consider 100-year intervals:

But the warming trend in 1909-2008 (the fastest “modern” 100-year trend) was +0.87 °C per century. The warming trend in 1663-1762 was +0.86 °C per century which is not excessively different. 😉 The fastest cooling, 1718-1817, was by -0.59 °C per century. Note that there are no quotas: the positive and negative trends don’t have to agree. In most cases, the maximum warming trends were faster than the fastest cooling trends. In some cases, namely the 10-year intervals, it was the other way around. Nothing should shock you here. They’re pretty much random numbers.

Conclusions

The Central England data show nothing unusual about the evolution of current temperatures. And because there is really nothing special about Central England, it’s reasonable to expect that no place in the world is experiencing anything unusual in the modern era, in comparison with other epochs since 1659.