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Sunday, May 15, 2016

Seven in a row: April is the hottest April on record, a 7000 year record?

Sou | 4:45 PM Go to the first of 16 comments. Add a comment

Yes, it's another hottest on record, this time in April 2016. According to GISS NASA, the average for April was 1.11 °C, which is 0.24 °C above the previous hottest April, in 2010. It's the equal third highest anomaly for any month (with January 2016), the highest being February, which was 1.33 °C.

The average for the four months to the end of April is 1.21 °C, which is 0.38 °C higher than any previous January to April period. The previous highest was last year, which with the latest data had an anomaly of 0.84 °C.

Longest stretch of hottest months in the record

This is the seventh month in a row of "hottest months", all of which had an anomaly more than one degree Celsius above the 1951-1980 mean. This breaks the previous record of six in a row, set last month. (See comment from Sheldon Walker below. There was six month run of "hottest" in 1997/98.)

This hasn't happened before in the record since at least the 1950s. Earlier times probably aren't sufficiently accurate on a month by month basis to say. I didn't check back that far and, in any case, pre-1950s temperatures would probably have been hotter at some time in the last couple of millenia. What that means is that 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 (and it's probably hotter now than it was back then).

Below is a chart of the month of April only:

Figure 1 | Global mean temperature anomaly - month of April only. Data source: GISS NASA.

You can see the global mean temperature trend by month in the chart below, for recent El Niño years:
Figure 2 | Global mean surface temperature for El Nino years. Data source: GISS NASA

Once again it was the high latitudes in the northern hemisphere that had the highest anomalies this month.
Figure 3 | Map showing mean surface temperature, anomalies for April, from the 1951-1980 mean. Source: GISS NASA

Below is March for comparison:

Figure 4 | Map showing mean surface temperature, anomalies for March, 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 April. This year is tracking well above 2015, probably mainly because of the current (fading) El Niño. To drop below the average for 2015, the average for the next eight months would need to be less than 0.62 °C:

Figure 5 | Global mean surface temperature, progressive year to date to March 2016. Data source. GISS NASA

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  1. I'm sure Eric Worral can make something up involving ignoring basic laws of physics that will reassure us all that nothing is wrong. Well maybe not us, but the inmates at WUWT will be happy.

  2. Sou,

    in this article for April, and a similar one for March last month, you have been highlighting the number of record months that there have been in a row.

    You have made a number of statements about these record months in a row which are not true.


    The first incorrect statement was made about the 6 record months in a row that ended in March. You said:

    "This is the sixth month in a row of "hottest months", all of which had an anomaly more than one degree Celsius above the 1951-1980 mean. Update: I did a quick check and that hasn't happened before in the record since at least the 1950s."

    6 record months in a row happened not long ago, from September 1997 to February 1998. It should be no surprise that this happened with an El Nino, the same as the current record months in a row.


    The next incorrect statement concerns how long it has probably been since there was a similar run of hottest months. In this article you guessed that it was probably more than 7000 years.

    That is incorrect, it happened about 73 years ago. There was a run of 9 (yes, nine) record months in a row from January 1944 to September 1944.

    This is a more extreme record than the current 7 months in a row, and it happened before man-made global warming had started.

    The December before this run of 9 months was not a record month. But the October and November just before that were also record months. So the were 11 record months in a 12 month period.


    When you think about the significance of the current 7 record months in a row, you should compare it to the 1944 9 record months in a row, and try not to jump to any incorrect conclusions.

    1. Thanks Sheldon, for picking those up. I'd checked the 97/98 years in particular, but obviously made an error.

      Your points are well taken and I'll correct the article.

      I'll just add - re the pre-1950 temps, there are two points as I made above.

      Firstly, there is much greater uncertainty in the observations than now (especially in the WW2 period).

      Secondly, the temperatures of the 1940s are much lower than those of this century. So while that run in the 1940s might be a "record" in the instrumental era, if you go back over the Holocene it would have happened in past periods and probably relatively recently (say the last couple of millenia or so). That means going back beyond the instrumental era over the Holocene as a whole or, say, the last 7,000 years, the 1940s temperatures wouldn't have been a record.

      By contrast, with this run, there probably haven't been temperatures as hot maybe in the entire Holocene, and almost certainly not for 7,000 years or so. That would mean they are the hottest in the record of at least the past 7,000 years or so.

    2. Something I've wondered about for a while --

      Sheldon Walker said 1944 was "before man-made global warming had started."

      Coal is today one of the primary sources of carbon dioxide pollution that is contributing to global warming. Back in the 1800s, we humans began burning fossil fuels (i.e., coal) in a big way. The records that go back to the 1880s certainly do show definite warming in the period 1880-1940.

      So here's the question: Why are so many people so certain that the coal burning from the Industrial Revolution pre-1944 didn't contribute to increased global temperatures before 1944, using the same mechanisms that coal burning is today contributing to increased global temperatures?

      What am I missing here?

    3. What's happened I think is that a lot of people latched onto the fact that probably *all* of the warming since 1950 is attributed to human activity, and decided that meant that *none* of the warming before 1950 was attributed to human activity.

      I see it so often that it goes right by me now. A lot of people seem to think it's like flipping a light switch. Up to midnight on 31 December 1949 burning coal and chopping down trees had no impact. From one minute past midnight on 1 January 1950 it suddenly did.

      Weird, I know. But that seems to be the notion on denier blogs all over. That is, that's what they think the science tells us. Of course deniers don't think that anything we do affects climate.

      Bill Ruddiman will tell you that we started affecting the climate thousands of years ago. I can't disagree.

    4. Thanks, Sou.

      I have a denier friend who uses this as a talking point -- "Half of all global warming happened before 1940, yet humans didn't start burning oil until WW2. What's up with that?"

      I keep pointing out, to no avail, that 1) the rise in temperature since 1970 is about twice what it was in the period 1880-1945, and 2) coal is also a fossil fuel (not just oil) and also contributes carbon dioxide to the atmosphere, and massive burning of coal began in the mid-nineteenth century.

      This seems to be a senseless denier zombie meme that just won't die.

    5. "So here's the question: Why are so many people so certain that the coal burning from the Industrial Revolution pre-1944 didn't contribute to increased global temperatures before 1944, using the same mechanisms that coal burning is today contributing to increased global temperatures?"

      Whilst coal burning did increase CO2 prior, it wasn't until the mid 20th century that CO2 emission.

      So as I understand it, whilst human activity probably contributed to some of the early 20th century warming, there wasn't a big enough increase in CO2 to have caused most of it.

      "This seems to be a senseless denier zombie meme that just won't die."

      Another point to consider is that the non-human factors that contributed to the early warming would not have contributed to the later warming. Skeptical Science has a page looking at this argument.

      The main factors causing the early warming were increased solar activity and low volcanic activity, neither of which have been a factor in the late 20th century.

    6. Thanks, Bellman.

      What I think you're saying (let me know if I get this wrong) is that most of the warming pre-1950 was due to non-human causes (though coal burning likely was a contributing factor). Going beyond the data you presented, we already know that more than all of the warming post-1950 is human-caused (i.e., were it not for human activity, the climate would be cooling; we are overwhelming the natural cooling forcings).

      The denialist argument about pre-1950 is a version of saying that since I got a flat tire by running over a nail, that means I can't get a flat from someone with a knife. That is, since the pre-1950s warming was primarily due to natural forcings, that means all warming must always be due to natural forcings, and human activity has to always be discounted.

      By the same argument, previous plagues were due to non-human-produced biological agents, so we needn't ever fear germ warfare. People die every day from natural causes, so there is no such thing as murder. And so on.

    7. Another point is that half the warming wasn't before 1940. If you take it from the coldest year to 1940, then from 1940 to 2015 actuals then the best you'll get is that 41% of the warming was before 1940. That's the only way to maximise the percentage before 1940, and it's quite a bit less than half.

      If you take a more reasonable approach and use a LOESS smooth, it will be less. Using the charts here you'll get around 25% of the warming from the coldest period to now happened before 1940. You can play with the numbers some, but you'd be hard pressed to show that 50% was before 1940.

    8. Dana at SkS indicated that increasing TSI (solar) and extra CO2 had about the same effect on temperature between 1910 and 1940, then the lack of volcanic activity also contributed. So maybe 1/3 human and 2/3 natural averaged over the period - roughly.

    9. That makes sense.

      So it seems we can safely say that Sheldon Walker's statement of 1944 being "before man-made global warming had started" is incorrect.

      We might as well call out this error in a comment intended to highlight an error.

    10. Fair play to Sou for entertainin' him. But I'm guessing your man Sheldon is not an honest broker. Quelle surprise.

    11. Another way of looking at it is the greenhouse warming trend in that period was so slight it cannot be distinguished from natural variability. The signal to noise ratio is low.

      Also the temperature records are not good, and probably inaccurate. I suspect no one really cared about a margin of error of several degrees, it isn't particularly significant compared to day-night variability.

  3. it has made front page of the BBC main news page

    or as a whutter would say the MSM "Bolshevik" Broadcasting Corporation

    1. I think folk also ignore that the northern Hemisphere went from a period of orbital cooling ( Had it not been cooling for over 1,000yrs?) into warming so there was a huge input of energy to halt and then reverse that cooling? Then we have the collapse of the Arctic ice shelfs along Ellesmere island ( and the formation of the floating 'T' islands?) ...which also must have taken some energy esp. coming off the "Little Ice Age"?
      We are overcoming some of the climate inertia but I do not believe we are yet seeing the full potential of the forcings we have unleashed?

    2. yes I was thinking about the concept of "inertia" the other day

      and actually I experience it quite a lot - although on a yearly scale

      I am a v keen windsurfer, and I have known for the last 30 years that the sea (around the UK) reaches its max temperature in November(ish) when the actual air temp can be very very cold

      likewise in spring even with high air temps the sea is very cold


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