USA Warming

Agree to Disagree

Debate in a non-hostile environment



USA Warming since 1900

The Legend for Global Warming Contour Maps can be found at the bottom of this page.


The Global Warming Contour Maps, and Line Graphs, in this article, are based on NOAA’s new ClimDiv temperature series. ClimDiv’s temperatures start in 1895, and it replaces the older USHCN temperature series (US Historical Climate Network). You can read about it here:

NOAA’s ClimDiv temperature series


The first Global Warming Contour Map in this article, gives you the “big picture” of USA warming since 1900. A very brief summary would be:

  • it warmed a bit
  • it cooled quite a lot
  • it warmed quite a lot

Graph 1 and 2

Overall, the warming was greater than the cooling, and the average warming rate for the whole period (1900 to 2018), was +0.85 degrees Celsius per century.

To make things easier to see, I have split the period from 1900 to 2108, into 3 periods of 50 years (with some overlap). Observant people will see, that small versions of the three 50 year contour maps, can be seen in the “big picture” contour map. The 50 year contour maps, show exactly the same things as the “big picture” contour map, but magnified for easier viewing.

I have tried to place the major warming and cooling events, into a 50 year contour map, so that events are not spread across multiple contour maps. Please note that this is based on my opinion, and nature does not necessarily agree with me.

We will look at each 50 year contour map, in turn, and see what we can find.


Graph 3 and 4

The first 50 year contour map, covers the period from 1900 to 1950. I am not a historian, but I have certainly heard about the warming in America in the 1930’s, and the dust bowl. There was an argument about whether 1934 was the warmest year in the 20th century. Whether it was, or whether it wasn’t, it was a close contest between 1934 and 1998.

The overall warming rate for 1900 to 1950 was +1.12 degrees Celsius per century. Please remember that the warming event in the 1920’s and 1930’s did not cover 50 years. So the warming rate that I just mentioned, includes quite a bit of cooling. The colours from this contour map shows that there were 30 year trends with a warming rate of over +3.0 degrees Celsius per century. We can compare this later on, with modern global warming.


Graph 5 and 6

The second 50 year contour map, covers the period from 1930 to 1980. The overall warming rate for 1930 to 1980 was -1.20 degrees Celsius per century. You can just see some warming on the bottom-right corner of the triangular contour map, as modern global warming begins.

There was short-term warming, even in the middle of this long period of cooling. Just after 1950 there was quite a large warming event, which had 10 year trends of greater than +4.0 degrees Celsius per century.


Graph 7 and 8

The third 50 year contour map, covers from 1970 to 2018. This is probably the most interesting 50 year period, because it is recent, and covers up to the present day. Is there anybody who doesn’t have an opinion about the recent slowdown? If the slowdown exists, then it should be visible in this contour map.

Before I discuss the slowdown, look at the colours on this contour map, It is dominated by red, and the overall warming rate for 1970 to 2018 was +2.86 degrees Celsius per century. Is there anybody brave (or foolish) enough, to deny that global warming is happening? The previous contour map was green, which meant cooling. This contour map is red, which means warming, and the warming is quite strong.

But the warming is NOT constant. Remember how in the previous contour map, there was short-term warming in the middle of the cooling. So why shouldn’t there be a short-term slowdown, or pause, in the middle of the warming in this contour map.

I am sick and tired of the slowdown “deniers”, who seem to fear that admitting that there was a slowdown, is the same thing as saying that global warming isn’t happening.

LOOK at the contour map. See the light-blue and dark-blue approximately triangular shape, near the bottom-right corner of the triangular contour map. The base of the triangle goes from about 2000, to 2010 or 2014. That is the slowdown.

If you don’t believe me, then look at the corresponding line graph, to the right of the contour map, See the flat (actually slightly cooling) line segment from 2000 to 2012. That is the slowdown.

So, I have shown you proof of the slowdown, not just once, but twice. Are you still going to be a denier? Note, these contour maps and line graphs, are based on USA data. So the slowdown definitely happened in the USA. I have been showing people contour maps and line graphs based on global data, for the last 2 years. But people still don’t want to believe me.

Anybody who wants to see evidence based on global data, should look at my web page on Slowdowns. The “Robot-Train contour maps” web page also contains a comparison between a Robot-Train slowdown, and a real global warming slowdown.