Tuesday, September 13, 2016

Crikey! Hottest August on record - vies with July for hottest month ever

Sou | 4:05 AM Go to the first of 17 comments. Add a comment
According to GISS NASA, the average global surface temperature anomaly for August was 0.98 °C, which is 0.16 °C higher than the previous hottest August in 2014.

Because July is the hottest month of the year, I've seen this July reported as the hottest month ever in recorded history! I asked the question whether August beat July and was told it's too close to call.

The average for the eight months to the end of August is 1.05 °C, which is 0.25 °C higher than any previous January to August period. The previous highest was last year, which with the latest data had an anomaly of 0.8 °C.

There are now eleven in a row of "hottest months" from October 2015 to August 2016 (that is, hottest October, hottest November etc). If we could look back over the entire Holocene, it's probably more than 7,000 years since there was a similar run of hottest months on record, that is, not since the Holocene climatic optimum (it's probably hotter now than it was back then).

Here is a chart of the average of 12 months to August each year. The 12 months to August 2016 averaged 1.03 °C above the 1951-1980 mean and was 0.23 °C hotter than the 12 months to August 2015:
Figure 1 | Global mean surface temperature anomaly for the 12 months to August each year. The base period is 1951-1980. Data source: GISS NASA

Below is a chart of the month of August only. Hover over the chart to see the anomaly in any August:

Figure 2 | Global mean surface temperature anomaly for the the month of August only. The base period is 1951-1980. Data source: GISS NASA

Now no La Niña?

You can see the global mean temperature trend by month in the chart below, for the strongest El Niño years since 1950, which were followed by a La Nina. I've included the 2015/16 period for comparison. NOAA has taken off the La Nina watch. The BoM ENSO update is due out later today.

Not counting 2015/16, of the seven very strong, strong and strong to moderate El Ninos since 1950, there were only three that were followed by a La Nina. The chart spans a three year period. That is, for the 2015-16 El Niño and subsequent, it goes from January 2015 to December 2017. (For a more detailed explanation see the HW articles: El Niño to La Niña years with more detail here.)

Figure 3 | Global mean surface temperature for strong or moderate/strong El Nino years that were followed by a La Nina. Data source: GISS NASA

Where was it hot?

Last month it was simply hot almost everywhere. There were cold patches over northern Russia and a few other places. Look at the map though. The orange and red are dazzling, and not in a good way.

Figure 4 | Map showing mean surface temperature, anomalies for August, from the 1951-1980 mean. Source: GISS NASA
Below is July for comparison:

Figure 5 | Map showing mean surface temperature, anomalies for July, from the 1951-1980 mean. Source: GISS NASA

Year to date average surface temperature

The chart below tracks the year to date. Each point on the plot is the average of the year to that month. For 2016, the last point is the average of all months to date including August. This year is tracking well above 2015, partly because of the El Niño. To drop below the average for 2015, the average anomaly for the next four months would need to be less than 0.49 °C:

Figure 6 | Global mean surface temperature, progressive year to date to August 2016. Data source. GISS NASA

The next four months would have to be the temperatures of 16 years ago...

Given the speculation that this will be another "hottest year", below is a chart showing the average temperature for the four months from September to December from 2000 onwards. To be cooler than last year, the average of the next four months would need to be less than 0.49 C. Only one year had the September to December average below 0.49 C and that was 16 years ago in 2000.

Figure 7 | Global mean surface temperature anomaly for the four months from September to December. The base period is 1951-1980. Data source: GISS NASA

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  1. The NOAA PDO index dropped to a negative number in August. JIASO's August PDO number is not out yet. I've been speculating that June's .79 ℃ could be the lowest monthly anomaly for 2016. GISS just adjusted it up to .80 ℃. The system is poised to have back-to-back El Niño events. Wouldn't that be cool?

  2. According to the global land/ocean climatology (1951-1980) of Berkeley Earth:
    the monthly absolute temperatures for July and August are 16.61 and 16.43 C respectively, a difference of 0.18 C. Since Gistemp August only is 0.13 C warmer than July, I would say that July still the is the "absolutely" warmest month, but within the error margin of course.

    I didn't expect such a strong temperature rebound in August. Now, it is relatively likely that the calendar year 2016 will stay above 1.00 C. It will if the remaining four months average at least 0.91 C..

    1. That's really amazing, isn't it? Gistemp didn't show a single monthly anomaly over 1C until last October, and yet we already have a real chance for the whole year to average over 1C. If you look at the "seasonal" year, i.e. December to November, it's extremely likely to be over 1C.

      Put another way, the "alarmists" of a year ago who said 2015 would blow away 2014 as the hottest year, and 2016 could be even hotter -- they were too conservative. 2016 could blow away 2015 by an even bigger margin.

  3. It's worth noting that NOAA has canceled its La Nina forecast and now forecasts ENSO neutral conditions through the fall and winter.

  4. Moving on. Last date of 30+ temps in Dutch de Bilt used to be 5 September. So today and tomorrow and perhaps Thursday will change this a bit...

  5. the UK has recorded the highest September temp since 1911

    "Temperatures in southern England peak at 34.4C, making it the hottest day of the year so far - and the warmest September day in 105 years."


    obviously on its own means little

    1. Well gee Tadaaa, you've just proven there has been no warming for 105 years using denier logic!!!

    2. Actually, that's just the first layer of denier logic. The second layer: the temperature measured in 1911 is genuine, the temperature measured in 2016 is fraudulent.


    3. Netherlands nationwide Sept record for minimum temp, was 20.9° C 5th 1949, today set at 21.6° C.

    4. @cRR

      yes, apparently the science suggests it is the minimums that are probably more important, but get less media space.

      Therfore it did not escape my notice that last year, when the UK was experiencing record winter temperatures - breaking 50/100 year old records, the media was all over the story

      but it was a tiny statement in one article that mentioned the fact that the all-time historical minimum WAS broken - that really grabbed my attention

    5. Min temp summer average for the US-contiguous was #1 in 2016 too.

    6. There is so very much that "... on its own means little." We've got to stop saying that. Instead, "... taken in context, this is scary as hell."

    7. Yes badly phrased by me, I suppose I was pre-empting jgnfld point

      It will be "rebutted" by a denier saying "it was warmer in 19?? Blah blah)

      It was more a point of picking your battles (in the online debate) a true record high minimum does not suffer the same retort

      It will inevitably get the "faked temp records" - which can then be countered with the

      "your a bat sh1t crazy conspiracy theorist"

  6. Sorry if I sidetracked you...but you know denier types will seize on anything which was the particular track I was pointing out.

    1. No problem. It was a fun diversion.

    2. Comment just seen on slate:

      Oh, the climate change certainly affects the weather. London, and some other parts of Europe are heading for the warmest September for more than 100 years. Our fault, no doubt.

      Wait a minute, doesn't this imply that it was at least equally as warm 100 or so years ago? Whose fault was that?!

      Don't say I didn't call it!


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