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2018 Was the Fourth Hottest Year on Record

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2018 was the 4th warmest year on record globally, and the 14th warmest for the contiguous USA.

Figure 1. Source: NOAA Centers for Environmental Information.

Figure 1 shows the average annual temperature for the Earth for each year from 1880-2018. The chart shows the temperature as an anomaly. That means that they calculated the mean annual temperature for the whole series, and then presented the data as a deviation from that mean. Degrees Celsius are on the left vertical axis, and degrees Fahrenhiet are on the right. Because the earth contains very hot regions near the equator and very cold polar regions, the actual mean temperature has relatively little meaning, and Climate-at-a Glance does not include it in their chart. (All data is from NOAA, Climate at a Glance.) 2016 was the highest on record, and the 4 highest readings have all occurred within the last 4 years. You can see that the Earth appears to have been in a cooling trend until around 1910, then a warming trend until mid-Century, then a cooling period until the late 1960s or early 1970s, and then a warming period since 1970. Over the whole series, the warming trend has been 0.07°C per decade, which equals 0.13°F per decade. Since 1970, however, the warming has accelerated to 0.17°C per decade (0.30°F).

(Click on chart for larger view.)

Figure 2. Source: NOAA Centers for Environmental Information.

Figure 2 shows the average yearly temperature for the contiguous United States from 1895 to 2018. In this chart and those that follow, the vertical axes are reversed, with °F on the left vertical axis, and °C on the right. The purple line shows the data, and the blue line shows the trend. 2018 was the 14th highest in the record at 54.58°F. The 4 highest readings have all come within the last decade. Over the whole series, the average temperature has increased 0.15°F per decade. Since 1970, however, the rate has increased substantially.

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Figure 3. Source: NOAA Centers for Environmental Information.

Figure 3 shows the average temperature across Missouri for 2018. Across the state, it was the 35th warmest year on record, with an average temperature of 55.2°F. In Missouri, the warming trend from 1930-1950 was more marked than it was nationally; across the whole time period, the trend has been for a 0.1°F increase in temperature each decade. As was the case nationally, since 1970 the increase has accelerated.

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Figure 4. Source: NOAA Centers for Environmental Information.

Because conditions in the Northern Rockies and Plains affect how much water flows into the Missouri River, which provides more of Missouri’s water supply than any other source, I have also tracked climate statistics for that region. Figure 4 shows the data. Last year was slightly above average for this region. This region has been warming at a rate of 0.2°F per decade over the whole period, and, since 1970, the rate has accelerated substantially.

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Figure 5. Source: NOAA Centers for Environmental Information.

Because I have been concerned about the water supply in California, I also track the climate statistics for that state. Figure 5 shows the data. Last year was the 3rd warmest year in the record, with an average temperature of 60.2°F. California has been warming at a rate of 0.2°F each decade. Since 1970 the rate of increase has accelerated substantially.

In all 4 locations the average yearly temperature seems to have increased significantly for several decades, then paused during mid-Century, and then resumed climbing, but at an accelerated rate. There seems to be little doubt that across the country it is warmer than it was. In Missouri, the average yearly temperature has been increasing, but at a rate that is somewhat less than in the other locations I looked at.

Sources:

NOAA National Centers for Environmental Information, Climate at a Glance. Retrieved on February 1, 2019, from http://www.ncdc.noaa.gov/cag.


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