Friday, August 16, 2019

Hottest July and hottest month on record

Sou | 5:23 AM Go to the first of 22 comments. Add a comment
Summary: July 2019 was the hottest July on record and the equal hottest month on record. The 12 month period to July 2019 was the third hottest  such period on record.

According to GISS NASA, the average global surface temperature anomaly for July was 0.93 °C, which is 0.08 °C warmer than the previous hottest - July 2016.

Below is a chart of the average of 12 months to July each year. 2019 averaged 0.93 °C above the 1951-1980 mean, which was 0.12 °C cooler than the 12 months to July 2016.

This makes it the third hottest August to July 12 month period on record after 2016 and 2017.

Figure 1 | Global mean surface temperature anomaly for the 12 months to July each year. The base period is 1951-1980. Data source: GISS NASA

Next is a chart of the month of July only. This July was also 0.93 °C above the 1951-1980 average and was the hottest July on record. It was 0.08 °C hotter than July 2016:
Figure 2 | Global mean surface temperature anomaly for the the month of July only. The base period is 1951-1980. Data source: GISS NASA

Where was it hot?

July this year is hotter overall than it was just a few years ago, and was hotter almost everywhere. Move the arrow at the left to the right to compare July this year with July of ten years ago, 2009.

May 18
April 18

Figure 3 | Maps showing mean surface temperature, anomalies for July 19 and July 09, from the 1951-1980 mean. Data source: GISS NASA

Equal hottest month on record

The chart below shows July this year is the hottest month on record, about equal with August 2016. That's especially notable because there is no El Nino this year, unlike back in 2016.

Year to date chart

For the record, here is the year to date progressive chart. You need to understand what it is to make sense of it. The chart below shows 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, which goes to July, 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.

So the 2019 year shows that the average for the period January to July is 0.97 °C. This is 0.12 °C lower than the average year to date for July 2016 (1.09 °C), toward the end of the massive El Nino.  The average over the entire 2016 year is 1.02 °C (the point marked for December on the 2016 line) and I'd be surprised if this year ended up with an average temperature hotter than that.

Figure 4 | Progressive year to date global mean surface temperature anomaly. The base period is 1951-1980. Data source: GISS NASA

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.)


  1. Replies
    1. It's a real worry, isn't it, Jammy. Makes you wonder what more is around the corner.

    2. Actually, it is an El Nino year, though a relatively mild one.


    3. It depends on whose word you take :)

      It met the criteria for NOAA but didn't meet the more comprehensive criteria set by the Australian Bureau of Meteorology.


    4. OK, not much of an El Nino then. Almost neutral.

      What I was trying to say is there is more to come.


  2. It's the hottest ice age on record.

    I do wonder how long it will be before IPCC reports will be telling us we will all have to eat insects, with the goal reduced to merely trying to ensure civilisation does not entirely collapse. And even then, the politicians will do nothing effectual, and the WUWT crowd will say its the sun or whatever.

    1. Interesting you say that, Andy. AFAIK insect food is being developed for the western palate but I don't know if any are sold yet, or any consumer trials conducted. If not, it won't be long. I expect it will appeal to people who want to eat less meat rather than vegetarians or vegans.

      This is from IPCC report Climate and Land just out: Insect-based diets
      Edible insects are, in general, rich in protein, fat, and energy and can be a significant source of vitamins and minerals (Rumpold and Schl├╝ter 2015). Approximately 1,900 insect species are eaten worldwide, mainly in developing countries (van Huis 2013). The development of safe rearing and effective processing methods are mandatory for utilisation of insects in food and feed. Some insect species can be grown on organic side streams, reducing environmental contamination and transforming waste into high-protein feed. Insects are principally considered as meat substitutes, but worldwide meat substitute consumption is still very low, principally due to differences in food culture, and will require transition phases such as powdered forms (Megido et al. 2016; Smetana et al. 25 2015). Wider consumer acceptability will relate to pricing, perceived environmental benefits, and the development of tasty insect-derived protein products (van Huis et al. 2015; van Huis 2013). Clearly increasing share of insect-derived protein has the potential to reduce GHG emissions otherwise associated with livestock production. No study to date however has quantified such potential.

    2. Andy, we aren’t in an Ice Age. We are in an interglacial period. Get a clue by doing some basic research!

    3. Be nice, Unknown.

      From ScienceDaily.com

      Glaciologically, ice age is often used to mean a period of ice sheets in the northern and southern hemispheres; by this definition we are still in an ice age (because the Greenland and Antarctic ice sheets still exist).

      More colloquially, when speaking of the last few million years, ice age is used to refer to colder periods with extensive ice sheets over the North American and Eurasian continents: in this sense, the most recent ice age ended about 10,000 years ago.

    4. The last 5 interglacial periods have all been comparable or warmer than our current interglacial. This is not hottest ice age on record.

    5. "...we are still in an ice age (because the Greenland and Antarctic ice sheets still exist)."

      Yes indeed. The Quaternary Ice Age began at the conclusion of the Pliocene, 2.58 Mya. Although the QIA is still ongoing, humans have injected nearly enough carbon into the system to eventually end it. As you say, referring to the most recent glaciation as an "ice age" is a colloquialism.


    6. I was (sarcastically) referring to the ice age we were supposed to be entering according to so many climate change deniers.

  3. Only three years to nearly terminate the latest version of "Da Paws." That was...rather fast. Someone (or something) seems to have revved up "the escalator."

    To illustrate, YT video by Dana Nuccitelli depicting the global temperature escalator ride from 1970 through 2016.


  4. Sou,

    One of the things I was missing during your sabbatical from blogging was your year to date temperature chart. With July being the warmest month on record I had been curious to see how the year was shaping up and thinking about how nice it would be to see the chart—so thank you!!!

    Question. Can you shed anymore light on the GISTEMP Seasonal Cycle chart? In particular, how does it deal with the Southern Hemisphere? Thanks.

    1. Thanks for the feedback, CC. I like doing these articles, though I've never been sure how useful people find them.

      Question. Can you shed anymore light on the GISTEMP Seasonal Cycle chart? In particular, how does it deal with the Southern Hemisphere? Thanks.

      To your question, I won't pretend to understand everything that goes into the analyses. Firstly, as I understand it, the seasons are just left as they are. That is, even though it's winter here, the hotter northern hemisphere more than makes up for that (because of the greater land mass, in part), so globally the hottest month is usually July.

      The seasonal chart uses MERRA-2 for the baseline data, and there's a write-up of that in J Climate. I understand different analyses will vary a small amount, depending on which product they use for the baseline(e.g. NCEP vs MERRA-2) - as well as how they work out the surface temperature anomalies.

      Then there's the matter of how to deal with missing data, such as from Antarctica which might be what you're referring to when you ask about the Southern Hemisphere. I don't have an answer for that. The MERRA-2 paper mentions it a couple of times.

      For it's surface temperature analysis, GISTEMP now uses GHCN v4 for land and ERSST v5 for oceans. There's a recent paper on Improvements in the GISTEMP Uncertainty Model, but I don't know if it covers how uncertainties in the Southern Hemisphere are covered.

      There's also a NASA press release on the new studies, confirming the temperature analyses are quite robust.

      I won't say any more as I'm not an expert in any of this. I just work with the data provided :) With luck, someone else will offer other insights.

  5. I agree with CC. I have missed these sorts of posts from you for the past while. Very informative and very well presented.

  6. Point of order: The reference period (1951-1980)was centered almost exactly on a period of declining temperatures (1945-1979,) which, interestingly, also coincided with a period of rapidly increasing CO2 levels. If the reference period had been 1910-1945 instead, a span that incorporated the record-breaking dust bowl years and also the year, 1940, in which the ice cover over the Arctic Ocean may actually have melted, the anomaly would have been much smaller. I would also like to point out that we have had pretty good data for the last third of the measurement period, sorta good data for the middle third, and not exactly great data for the first third. So take with a grain of salt. I would further like to point out that the start point of the measurement period was, more or less the last gasp of the Little Ice Age, so it kind of makes sense that there would be an upward rebound following that quite cold spell. Perhaps most of what we are seeing is rebound to the Holocene normal from the downward deviation of the LIA. No?

    1. No.

      The LIA was part of a longer 5000 year cooling trend which went into reverse from about 1910.


      Look at only the natural changes and one would expect 0.05C cooling since 1880, continuing the long term trend. Instead we have 1C warming.

    2. Entropic man is correct.

      feral-nerd has a new twist on "it hasn't warmed since 1998" which morphed into "it hasn't warmed since 2016", which is going to have to morph into some later year very soon.

      Picking a peak and trough to claim "it hasn't warmed since ...", and a highly suspect peak at that (WWII), pens you as a denier feral-nerd, as much as everything else you wrote in your comment.

      The reference period of 1951-1980 is about as close to the 20th century average as you're likely to get. The difference is only -0.033 C. (Using an early period, as feral-nerd inconsistently points out, brings in uncertainties because records are much better from mid-century onwards. As well as that, it doesn't change the overall trend, which is up..up..and ever higher.)

      To imply that this is no more than a "bounce" from the little ice age is immensely stupid. It marks feral-nerd as a greenhouse effect denier. What do you think is causing this mysterious bounce and when do you think gravity will decide to exert itself and cause another ice age? (Since feral-nerd doesn't believe in the greenhouse effect, one wonders if his bounce theory is that gravity causes ice ages or some other wacky notion.)


    3. Feral science-denier, Entropic man and Sou have already corrected you on the facts of the Holocene cooling and the Industrial Revolution reversal of the post-Holocene maximum trend. All that aside though, your attempt to make anomalies "much smaller" completely misses the additional fact that anomalies are calculated precisely to make the value at any point on the abscissa irrelevant at that point - it is the value relative to the entire span of data along the axis that matters: that is to say, the trend. The trend is not changed in the slightest by the reference baseline used to determine the anomalies.

      In other words, one could use the averaged baseline as it existed during the life of Christ, and the current global warming would still be as implacably evident as it is in the graphs above. The only possible reason for attempting to construct a baseline as you suggested is to attempt to minimise in people's minds the perception of the significance of the current warming. This is not only intellectual laziness/ignorance, it's outright intellectual mendacity.

      And quite frankly, if one is going to attempt to redefine the baseline for contemporary warming, one should use as a reference an objective period such as the span from1750-1800, which represents the beginning of the Industrial Revolution after the rebound from the Little Ice Age, and a span where temperature was about as minimally unaffected by modern human activity as it can be, and without the superimposition of large natural fluctuations. Under that senario we'd be at a current anomaly value of around 1.2 C, which rather more greatly informs the significance of the warming trajectory to which we've committed the planet if one is going to sweep under the carpet the trend of the last several centuries…


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