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2014 Was the Hottest Year Ever Worldwide

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2014 was the hottest year ever worldwide, according to the State of the Climate in 2014 report by the American Meteorological Society. This is a report that came out in July, 2015, and I’m just catching up to it now. I will summarize a few of the many findings.

Figure 1: Global Surface Temperature Anomalies, 2014. Source: Blunden & Derek 2015.

Figure 1: Global Surface Temperature Anomalies, 2014. Source: Blunden & Arndt 2015.

Figure 1 shows how much 2014 temperatures around the globe varied from the average temperature for that location (reference years 1981-2010). The yellow and red areas were warmer than average, the blue areas cooler. Gray represents areas for which there is not enough data to make a characterization. You can see that the map has many more yellow and red areas than blue. Across 5 different data sets, the temperature over land was .39°C hotter than average, the temperature over ocean was .22°C hotter than average, and for the whole world was .26°C hotter than average.

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Figure 2: Global Surface Temperature Trends. Source: Blunden & Derek 2015.

Figure 2: Global Surface Temperature Trends. Source: Blunden & Arndt 2015.

Figure 2 shows the trend in global temperatures from 1880 to 2014. The top two graphs represent different analyses of both land and ocean, the middle two graphs represent different analyses of land only, and the bottom two represent different analyses of ocean only. All of the charts show a consistent and continuing warming trend that began in 1910, and perhaps earlier than that.

One of the ways global warming has its effect is by increasing the number of “warm” days. What is a “warm” day? That’s actually a bit involved to explain. Here goes: to start with, study the 30-year period from 1961 to 1990. For each date – each February 2nd, for instance – there is an average temperature on that date for each year. List the average temperatures on February 2 for all of the years. Since there are 30 years, there will be 30 average temperature. Determine the hottest 10% of them. In this case, since there are 30, the hottest 10% would be the hottest 3. Look at the lowest of the 3. That becomes the cut-off temperature.

Figure 3: Global Warm Day Anomalies, 2014. Source: Blunden & Derek 2015.

Figure 3: Global Warm Day Anomalies, 2014. Source: Blunden & Arndt 2015.

If the temperature on February 2 in 2014 is hotter than the cut-off, it counts as a “warm” day. Now do that same procedure for every date in the year. Now count the number of “warm” days in 2014. Now divide that number by the total number of days in 2014 and multiply by 100 to yield a percentage. Subtract 10% from the calculated percentage to yield the anomaly. That is what is shown in Figure 3.

Here’s another way to say it: in Figure 3, northeastern Europe and northwestern Russia ar colored dark red. That means they have an anomaly of 10. That means that 20% of the days in 2014 were hot enough to fall in the range that defines the hottest 10% of days in the reference period (1961-1990).

You can see that in Figure 3 there are large blobs of red over Australia, Southeast Asia, China, parts of India, Europe, Northeastern Russia, Greenland, and western North America. That means that all these regions had an increase in the number of warm days. Middle and Eastern North America, on the other hand, had fewer.

In the summer a “warm” day might indicate that it was extremely hot, which is hazardous. During the winter, on the other hand, it might indicate that the day was above freezing. In regions that depend on their snowpack to last into the summer, winter melting can be a problem.

Figure 4: U.S. Temperature Anomalies, 2014. Source: Blunden & Derek 2015.

Figure 4: U.S. Temperature Anomalies, 2014. Source: Blunden & Arndt 2015.

For the United States the situation was a bit different. Figure 4 shows the pattern. A winter outbreak of frigid winter weather kept average temperatures in the central parts of the country down, and to a lesser extent the east as well. Throughout the West it was hotter than average, with 2014 being the hottest year on record in California, Arizona, Southern Nevada, and Western Oregon.

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Figure 5: U.S. Temperature Trend. Source: Blunden & Derek 2015.

Figure 5: U.S. Temperature Trend. Source: Blunden & Arndt 2015.

Figure 5 shows annual mean temperatures for the contiguous United States for 1895-2014. There are some pretty wide swings from year to year, but the pattern shows a clear trend of increasing temperature of about 2°.

The report is not fine-grained enough to speak directly to the situation in Missouri. Still, it shows that the worldwide trend with regard to temperature continue to be upward. Many other climate variables are also reported, and most of them continue the trends that have been in place for the last several decades. All are consistent with what would be expected as a result of global warming.

I’m writing this post in early January, 2016. Climate data for 2015 should post-up on Climate at a Glance during January, so hopefully by the time this post goes live, I’ll be able to follow up with information about the USA and Missouri.

Source:

Blunden, Jessica and Derek Arndt (eds.) 2015. “State of the Climate in 2014.” Bulletin of the American Meteorological Society, 96 (7) Special Supplement. Downloaded 1/4/16 from http://journals.ametsoc.org/doi/abs/10.1175/2015BAMSStateoftheClimate.1.

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1 Comment

  1. […] map of warm days for 2015 looks quite similar to the map for 2014 (here): many of the same areas were […]

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