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Summary: 2019 was the second hottest year on record. December 2019 was the second hottest December on record. The last decade was the hottest decade on record.

According to GISS NASA, the average global surface temperature anomaly for 2019 was 0.98 °C, which is just 0.04 °C cooler than the previous hottest – 2016.

Below is a chart of the average of 12 months to December each year. 2019 was 0.06 °C hotter than the 12 months to December 2017, which is the third hottest year.

Figure 1 | Annual global mean surface temperature anomaly – 12 months to December each year. The base period is 1951-1980. Data source: GISS NASA


Next is a chart of the month of December only. This December was 1.11 °C above the 1951-1980 average and was the second hottest December on record. It was 0.05 °C hotter in December 2015 which, unlike this past year, was in the middle of a strong El Nino:

The decades are getting hotter

As you would know, each decade is getting hotter and hotter. Each of the five decades since 1971-1980 has been hotter than the previous one. The chart below shows what’s happening. It includes a line showing the mean for the 20th century. Note the last column only includes nine years – to 2019. Let’s see what next year brings.

Figure 3 | Global mean surface temperature anomaly by decade. The base period is 1951-1980. Data source: GISS NASA

Where was it hot?

Last year was hot almost everywhere. The only year that was hotter was 2016, but that year there was more contrast. In 2016 there were hotter parts and colder regions compared to last year. The hot Arctic helped drive the average temperature in 2016. 

Move the arrow at the left to the right to compare this year with 2016. Check out Australia, too, where 2019 was the hottest year on record.

May 18
April 18

Figure 4 | Maps showing mean surface temperature, anomalies for 2019 and 2016, from the 1951-1980 mean. Data source: GISS NASA

July 2019 was the hottest month on record

The chart below confirms July this year was the hottest month on record, hotter than August 2016. The chart indicates the changes in monthly temperatures and shows the hottest months of the year are in July and August. (Sometimes it’s July that’s the hottest month and sometimes it’s August.) I added a dotted line to the chart to make it easier to see. As I said previously, that’s especially notable because there was no El Nino this year, unlike back in 2016.

Figure 5 | Seasonal cycle of global surface temperature anomaly. The chart shows the temperature anomaly with respect to the 1980-2015 (°C) mean. It is derived from the MERRA2 reanalysis over 1980-2015 and shows how much warmer is each month of the GISTEMP data than the annual global mean. Source: GISS NASA

Year to date chart

Below is the final year to date progressive chart for 2019. What it shows is the average temperature for the year at each point on each separate line on the chart. The topmost line is 2016. The fat black line with dots is 2019.

For each year at January, the point is just the anomaly for January. At February, the point is the average anomaly for January and February. At July, it’s the average of January to July inclusive – all the way to December, which is the average for the whole year.

Back in July I wrote:

It’s not out of the question that 2019 will end up the second warmest year on record, ahead of 2017. (The temperature anomaly for the rest of the year would have to average 0.87 C for 2019 to equal 2017.)

The temperature anomaly for the rest of the year, from August to December, averaged 1 °C, so it easily beat 2017 for second place.

The 2019 line shows that the average for the year is 0.98 °C (the last big dot on the 2019 line). This is just 0.04 °C lower than the 2016 (1.02 °C). Unlike 2015/16, there was no El Nino this past year, at least not using Australia’s BOM criteria.

Figure 6 | Progressive year to date global mean surface temperature anomaly. The base period is 1951-1980. Data source: GISS NASA



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