2016 was the hottest year on record for the troposphere

For the troposphere, 2016 was the hottest year on record!

The troposphere temperatures for December 2016 have been released. The lower troposphere is recorded in UAH v6 beta 5 and RSS TLT v3.3. This report also covers RSS TTT for the troposphere (without the "lower") and follows pretty much the same format as previous monthly updates.

For RSS TTT (troposphere), 2016 was the hottest year in the record. Last month was the second hottest December on record.

The lower troposphere (UAH beta v6.05) also showed 2016 as the hottest year in the record. However, December was only the sixth hottest December on record, with 2015 the hottest.

Troposphere temperature (RSS TTT v4) chart

First here is RSS TTT with the latest dataset, version 4. TTT seems to measure more of the troposphere than TLT (that is, it has a greater vertical profile) with less of the stratosphere than the mid-troposphere data (TMT). It shows a higher rate of warming than RSS v3.3 and higher than UAH. Hover the cursor (arrow) over the plots to see the data points, trend etc.

The chart below is the average of the 12 months to December each year from 1979 through to 2016. The annual averaged anomaly was 0.78 °C, which is 0.17 °C higher than the previous hottest year, 1998. The rate of warming is 0.18 °C/decade or 1.8 °C/century.

Figure 1 | Troposphere temperature for 12 months to December (TTT). Anomaly is from the 1979-1998 mean. Data source: RSS

From the RSS website, TTT is derived from TMT and TLS with the formula:

TTT = 1.1*TMT - 0.1*TLS. 

This combination reduces the influence of the lower stratosphere, which is cooling at most locations. TLT gives most weight to the temperatures closer to the surface. TTT gives more weight to the troposhere and less to the stratosphere than TMT does, but not as much to the lowest levels of the troposphere as TLT does. However TTT has version 4, while TLT is still only provided as version 3.3. For a fuller explanation see the RSS website or the July 16 report here.

Below is the TTT chart just for the month of December. The anomaly for December was 0.527 °C, which is 0.101 °C cooler than December 2015. The rate of warming just for December is 0.15 °C/decade.

Figure 2 | Troposphere temperature for the month of December only (TTT). Anomaly is from the 1979-1998 mean. Data source: RSS

Lower troposphere

The rest of the charts are from UAH beta v6.5. This is almost identical to the old version of RSS, which is v3.3, so is likely to be updated at some time. (Other RSS data sets, like TTT are now at version 4.)

The chart below is the annual average from 1979 to 2016. 2016 is the hottest on record by 0.03 C.

Figure 3 | Lower troposphere temperature for 12 months to December. Anomaly is from the 1981-2010 mean. Data source: UAH

Below is the UAH chart for the month of December only for each year going back to 1979. The anomaly was 0.24 °C above the 1981-2010 mean, which was only the sixth warmest December in the record, and 0.23 C cooler than the hottest December in 2015.

Figure 4 | Lower troposphere temperature for the month of December only. Anomaly is from the 1981-2010 mean. Data source: UAH

Comparing recent ENSO years

Below is a chart comparing the strongest El Niño years since 1979, which were followed by a La Niña, just for UAH v6 beta 5. I've included the 2015/16 period for comparison.

Figure 5 | Global mean lower troposphere temperature for strong or moderate/strong El Nino years that were followed by a La Nina. Data source: UAH

La Nina didn't end up happening. The odd thing is that even though it didn't emerge in 2016, the UAH December temperature has dropped back to the level of the December 1998, when there was a La Nina. I still think the UAH data record as a whole would be quite different if satellite drift were better accounted for by UAH - going by comparison with RSS data.

That's all for 2016 from the troposphere, at least as far as temperature articles go. From now on the monthly updates will be for 2017. I might even change the format, for a bit of variety:)

Update from RSS

This news release from Remote Sensing Systems (RSS) just arrived by email. Worth clicking the link because there are a lot of charts:

Using the latest version (Version 4.0) of the “Temperature Total Troposphere” (TTT) dataset, RSS scientists showed that 2016 was 0.31 degrees F warmer than the previous record, set in 1998. The third warmest year occurred in 2010. In addition, 9 out of 12 months for 2016 were the warmest of that month ever recorded in the satellite record. By this we mean that January 2016 was the warmest January, etc., for all months except for May, June and December (the December record was set in 2015). The record warmth was caused by long-term global warming combined with the strong El Niño event that occurred in the winter and spring of 2015-2016. …

…For this work, we used the “Temperature Total Troposphere” (TTT) dataset instead of the more commonly cited “Temperature Lower Troposphere” (TLT) dataset. TTT measures the temperature of a thick atmospheric layer, extending from the surface to about 8 miles (about 13 km) high. We use TTT because TTT has been updated to version 4.0, while version 4.0 TLT is not yet available. (We use TTT instead of TMT because the latter has not been corrected for the influence of stratospheric cooling.) In the upgrade to version 4.0, we improved the method we use to correct for drifting satellite measurement time, leading to more reliable measurements, particularly since 1998. The new version shows more warming than the older version, particularly since 1998.

For more details see: Mears, C. A. and F. J. Wentz (2016). "Sensitivity of Satellite-Derived Tropospheric Temperature Trends to the Diurnal Cycle Adjustment." Journal of Climate 29: 3629-3646.

This paper is available online (open access) http://journals.ametsoc.org/doi/10.1175/JCLI-D-15-0744.1

RSS TLT version 3.3 contains a known cooling bias. We are working to eliminate the bias in the new version of TLT. Even with these known cooling biases, 2016 was a record warm year in TLT v3.3. In fact, 2016 was a record warm year in all RSS tropospheric temperature products (TLT v3.3, TMT v3.3, TTT v3.3, TMT v4.0 and TTT v4.0) 

Here is one of the charts, showing how new records keep being set over time, particularly in 2016. A red dot means a hot record and a blue dot means a cold record. I've added small black arrows down the bottom so you can more clearly see which years are 1980, 1990, 2000 and 2010.

As you'd expect, there were more records of both types in the early years of the data set. There have not been any cold records set since 1993. In 1998 there were a ten record hot months, all but two of which were broken again in subsequent years. In 2016 there were nine record hot months.

Added by Sou at 10:45 am AEDT 6 Jan 2017 (11:45 pm GST 5 Jan)