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Monday, July 20, 2015

Watching the global thermometer - year to date GISTemp with June 2015 with corrections

Sou | 4:49 AM Go to the first of 13 comments. Add a comment
Note: This includes the corrections just announced by GISS and replaces the previous article - see comments here. (h/t David Sanger)

Every month since March, I've posted a chart of the progressive year-to-date global average surface temperature, from GISS. This is the update with June included. I'll repeat the explanation with each update and add what seem to be things to watch.


I've added a chart of annual temps for GISTemp, comparing the version put out in June with the (corrected) version put out in July. That's so that you can see what difference the shift to ERSST v4 makes.

Worth noting - now with corrections from GISS

  • June was an average of 0.80°C above the 1951-1980 mean and is hottest June on record.
  • No other month this year was hottest on record.
  • The highest anomaly this year is now March at 0.90°C, which makes it the third hottest March after March 2010, at 0.92°C and March 2002 at 0.91°C.
  • 2015 is still hottest on record so far. With the adoption of ERSST v4, some of the temperatures are higher. So are those of some other years, particularly in 2010, temperatures have been upped quite a bit. But all have changed.
  • April and May are still relatively cool, unlike in some other data sets. By cool I don't mean cold. May was 0.76C above the 1951-1980 mean. It's just that most people thought it would be among the hottest of Mays, particularly since ERSSTv4 was very high in May this year.
  • The lowest anomaly was in April this year, at 0.74°C above the 1951-1980 mean. 
  • The progressive year to date average up to and including June is 0.82°C above the 1951-1980 mean. In June 2010 it was 0.78°C above. (In June 2014, the hottest full year to date, it was 0.72°C above.)




Explaining the chart


The chart is a progressive year to date average for all years from 1995 to the present. What that means is for January each year, it just shows the anomaly for January. For February it shows the average of January and February for each year. For March, its the average of the monthly anomaly from January to March.

If you look at December, each year shows the annual average temperature for the full year. For November, each year has the average for the year up to November, not including December. (As before, I've made it extra large because of all the fine detail.)

Data Source: NASA GISS

2015 is still tracking as the hottest on record. The years to watch are 2014, 2010 and 2005. I've plotted them with slightly thicker lines so they stand out more easily.

The coldest year of the lot was 1996, which still ended up more than 0.3°C above the 1950 to 1981 average.  The next time someone tries to tell you that "it hasn't warmed since 1996" then show them this chart :)


GISTemp changes with ERSST v4


Now that GISTemp is using ERSST v4, the temperature data has changed some over all years. Below is a chart showing the annual average for the June version and this latest July version, which uses ERSST v4. I've also plotted the difference between the two versions. It's really piddly in the whole scheme of things as you can see. (There's some discussion of ERSST v4 in this HotWhopper article about NOAA revisions).

Data Source: NASA GISS

Points to note:
  • The 2015 temperature for both series is year to date average to May (not including June), so they can be compared.
  • The "difference" is the July version minus the June version. Positive means the July version is higher than the June version.
  • As you can see, the biggest difference is 1944 and 1945, which are 0.13 and 0.12 respectively. Most years it's +/- 0.01C to 0.05C. 
  • The July version is higher than the June version at both ends. There's barely any difference in the middle of last century. 
  • The biggest changes are in the more recent years but it's not the same every year. (Eg increases from 2009 onwards are larger than in the late 1990s). 
  • There's that questionable peak in the 1940s that someone will undoubtedly be able to sort out one of these days. (Probably because something different happened on war vessels to how the temps were usually taken.)
  • Click here to see a spreadsheet showing the differences with this version with ERSSTv4 over previous version with ERSST v3b.
Below is the difference between the two versions only - blown up, so you can see it more easily:



Related updates



Here is the link to the table for the top Year to Date chart.

13 comments:

  1. Let me be the first to predict that if 2015 sees a strong El Nino and winds up 0.10 °C warmer than 2014 that the fake skeptics will be lined up stating

    How many thermometers did they have in 1840?
    They can't even measure temperatures to better than 0.2°
    More 'adjusted' temperature data from NOAA hahahah
    What's the temperature of the Earth even supposed to mean?
    My summer wasn't warm at all
    If they're 98% 'sure' that means they're 2% not sure
    Sure it's warming, it's always warming up and down

    (That's enough, I feel my IQ dropping as I type)

    ReplyDelete
    Replies
    1. You missed "It's snowing. So much for global warming".

      Delete
    2. Christopher Monckton got his prediction in first : if the El Nino persists until the Paris conference it will be used to stoke a panic atmosphere justifying the imposition of Agenda 21 according to secret protocols known only to him, Obama, and the Red Priest. Or something closely akin to that. Whatever, this is a critical time.

      Delete
  2. Sou, thanks for re-doing the difference as new - old. I know it doesn't matter so long as you know how it was calculated, but it's the same way I've seen it represented elsewhere, and I think it's more intuitive that way.

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  3. Hmm, I have to say I'm not a big fan of all of these annual comparisons. My personal preference is for a running annual average, ignoring arbitrary calendar divisions.

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    Replies
    1. If I understand you, the annual average chart is up there too. If you'd like me to plot something different as well, let me know how you'd like it, Steve.

      Eg I can add a moving annual average to the annual average (like the second chart above) as in this chart (with an 11 year MA) - or just plot the MA separately if you like.

      Delete
  4. Yes, moving is what I meant. IMO annual averaging would be better in terms of showing recent variability, being enough to get rid of the seasonal cycle but no more than that. 11-year (solar cycle, presumably) seems overly smoothed. Also, as the graph would contain current information, is there some reason not to show it up to the most recent available month rather than six months back? (I do realize the information is the same and that this would just result in moving the curve to the right.) Finally, since there is value to showing the moving average relative to shorter-term change, maybe do seasons (less busy-looking than months) as single points. I'm trying to think of this in terms of how well the graph communicates the trend to people who lack experience with looking at such things.

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    Replies
    1. I think you'll have to settle for either an annual moving average or a monthly moving average, Steve. It's really got to be one or the other. I can't mix and match annual with monthly. (I suppose I could pick a different 12 month period - eg 12 months ending on the current month - but not sure what purpose that would serve.) The monthly will have a lot more wiggles than the annual, of course. (The top chart above shows the year to date average for each month, up to the most recent month available.)

      GISTemp does provide monthly (as you can see above). However to do a monthly moving average spanning years means a tedious amount of time reformatting (it comes in a 2D table - year by month, not in single column). Maybe you could get it in R, but I haven't been using that. Or you can choose another dataset, like HadCRUT4, which is set out in a suitable manner. However I don't really like monthly charts as a rule, because they are way too noisy and hide the signal. (I frequently criticise WUWT for showing monthly, which I suspect they do for that very reason.) In any case, it won't show up what the above chart is intended to show as clearly IMO.

      For now, I'm happy to add an annual moving average of whatever is your period of choice. I suggest not less than five years, or it might as well be just the annual average. And not more than eleven years or, as you say, it's too smoothed.

      The top chart in this article is for a particular purpose. Apart from having set it up so it's easy to plot, I like it as a different way of keeping up to date with how the temperature is tracking is because:

      a) you can see at a glance how this year compares with other years - is it tracking first, second or third (in this case it's still the hottest on record for the time of the year as well as overall). A lot of people like to see whether the current year will be another "hottest" or not :)

      b) This way of showing it also helps put things in perspective. It shows that just because a year to date average is high, doesn't mean it will stay high all year. You just need a couple of colder months and a year can drop from looking to be the hottest to fourth place. Or a couple of warm months to lift it up to first place (as in 2014).

      I post temperature charts a lot. This is the only regular article where I plot in this way - after the monthly GISTemp is released. Mostly I plot annual or decadal for surface temp (with or without a moving average). For climate monitoring (as opposed to weather watching) I prefer decadal charts of surface temperature, like the ones shown on the main chart page:

      http://www.hotwhopper.com/Charts/charts6.php - for example this one. Or metrics other than surface temperature - like sea level, ocean heat content, arctic sea ice etc.

      Delete
    2. Sou, sorry for the off-topic.

      Steve, do you still have the same e-mail address? I've tried to mail you a couple of times, but no answer.

      Delete
  5. The update doesn't surprise me, but I'm sure that it won't surprise the Denialati either, though for very different reasons. They'll be crying "conspiracy!" from the rooftops for sure.

    The 0.80 anomaly is however consistent with the figures that other agencies were releasing a few weeks ago before GISS finally caught up. Looking at the trends in those those other agencies' values I expected 0.80-0.81. Frustratingly I can't find the web page that tabulated all the different anomalies in one place - if anyone knows to which page I'm referring I'd be much obliged.

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  6. Replies
    1. Thanks David, that was the place.

      The more I look at these graphs, the more my blood chills. It's a massive, massive train wreck in century-scale slow motion...

      Delete

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