Another "hottest month": Troposphere temperatures for September 2016

The troposphere temperatures for September 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.

In all records, the September global anomaly was higher than it was in August but lower than earlier this year as El Niño is now over.

For RSS TTT (troposphere), last month was the hottest September on record. For 2016 to be colder than the previous hottest year (1998), the troposphere would have to average a negative anomaly:- less than -.025 °C for the remaining months.

The lower troposphere (UAH beta v6.05) was the equal hottest September on record with 1998. For 1998 to remain the hottest year in the UAH lower troposphere record, the average for the next three months would need to be below 0.28 °C, which could happen. (Roy and John changed the August 2016 temperature, dropping it from 0.44 °C to 0.43 °C.)

Troposphere temperature (RSS TTT v4) chart

First here is RSS TTT with the latest dataset, version 4. TTT seems to be 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 September, from October 1979 to September 1980, through to October 2015 to September 2016. The 12 month averaged anomaly was 0.78 °C, which is 0.19 °C higher than the previous hottest 12 month periods in 1998 and 2010. The rate of warming is 0.18 °C/decade.

Figure 1 | Troposphere temperature for 12 months to September (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 September. The anomaly for September was 0.806 °C, which is 0.141 °C warmer than September 2010. The rate of warming just for Septembers is 0.23 °C/decade.

Figure 3 | Troposphere temperature for the month of September 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 average of the 12 months to September, from October 1979 to September 1980, through to October 2015 to September 2016. The past 12 months is the hottest on record by 0.05 C.

Figure 4 | Lower troposphere temperature for 12 months to September. Anomaly is from the 1981-2010 mean. Data source: UAH

Below is the UAH chart for the month of September only for each year going back to 1979. The anomaly was 0.44 °C above the 1981-2010 mean, which was the same as September in 1998.

Figure 5 | Lower troposphere temperature for the month of September only. Anomaly is from the 1981-2010 mean. Data source: UAH

Below is the UAH chart for the average of the nine months to September each year for comparison. In 1998, the average for the nine months to September was 0.56 °C, which is 0.01 °C higher than the average for the nine months to September in 2016. In 1998, the average for the 3 months from October to December was 0.26 °C. It would take a similar drop for 1998 to remain the hottest in the UAH beta v6.05 record (see Figure 7 below).

Figure 6 | Lower troposphere temperature for the 9 months to September each year. 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 v6beta. I've included the 2015/16 period for comparison.

Figure 7 | Global mean surface temperature for strong or moderate/strong El Nino years that were followed by a La Nina. Data source: UAH

La Nina might still appear this year according to BoM, though it is not very likely. (Maybe next year.)

From the WUWT comments

The comments below are from the WUWT copy and paste of Roy Spencer's latest article about the UAH lower troposphere record (archived here, latest here). One interesting thing is that even a few days later there are only 55 "thoughts". WUWT-ers may be getting despondent. The rush to claim that UAH temps show an ice age is coming have almost, but not quite, dried up.

Another interesting thing - no sub-head. Here are the sub-headlines from WUWT for previous articles - there wasn't one for September:

• September: 
• August: "August 2016 and 2016-to-date are second warmest"
• July:: "July Temperature Recovers Slightly from Previous Free-Fall",
• June:: "Spectacular Drop In Global Average Satellite Temperatures".

Yet another interesting thing. Anthony Watts' main WUWT headline was way wrong this month: "September Global Temperature Unchanged from August – but still cooler than 1998 or 2010".

The September temperature is not cooler than it was in September 1998 or September 2010. Nor is the 12 months to date. The 1998 year to date (Jan to Sep) was 0.01 C higher than this year so far however the year to date in 2010 was quite a bit cooler (by 0.15 C).

The WUWT comments indicate that some WUWT readers are not very good at reading charts or doing arithmetic. Some are better - Donald L. Klipstein did alright:

October 3, 2016 at 4:31 pm
According to the text data file, if I read it right, September of 2016 was not cooler than September of 1998 (tied at .44 degree anomaly) or September of 2010 (which was cooler at .37 degree anomaly).

afonzarelli tried to justify the wrong WUWT headline, foolishly writing:

October 3, 2016 at 5:11 pm
Yes, but still, temps are now lower than they were in ’98 & ’10 (at both of their peaks in temps)…

 Yeah - the September temperature is also lower than the peak in 2016, which is higher than the peak temperatures in 1998 and in 2010. See Figure 7 above.


bazzer1959 thinks that there might be some explaining to do:

October 4, 2016 at 12:12 am
A month ago, I warned that the decline in temps may NOT happen. Quite a few on here rushed to say there was nothing of any concern. I say again, if temps don’t cool VERY soon, we have some explaining to do. I really do think that, post El Nino, temps should have cooled.

ironicman agrees, sort of:

October 4, 2016 at 2:04 am
If it doesn’t cool soon then the lukewarmers win. 

Not richard verney, though, who looks on nature as a God who dictates whatever it wants, even if it defies its own laws:

October 4, 2016 at 2:20 am
“If it doesn’t cool soon then the lukewarmers win.Why? If all temperatures are naturally driven, it follows that if there is no further cooling that is the result of what nature dictates; it does not follow that it is the result of modest warming from the increase in CO2.

RWturner imagines some cooling trend. He or she does not live in this world.

October 4, 2016 at 11:02 am
There is still plenty of cooler than average water in the subsurface tropical Pacific that will surface over the next few months and La Nina’s typically develop at this time of year if they are going to materialize. This will continue the cooling trend.

waclimate complained, wrongly, that BoM and "the Australian media" didn't do something that a check shows they did:

October 4, 2016 at 5:29 pm
And when the BoM and Australian media don’t mention that the south west quarter of Australia, pushing towards a million sq km, had its coldest September mean temperature since 1897 during what UAH suggests might be the world’s hottest year, I think it’s worth mentioning.