We just had the warmest “year” again

A year is 12 months long. It is also the period of time between January and December, inclusively. But you can use that first definition (we do it all the time) when appropriate. So, we can ask the question, how does the last 12 months, ending at the end of January 2015, compare to previous 12 month time periods in terms of global surface temperature?

We can do this using a moving average. A moving average for a series of values is the average of a certain number of values in sequence, calculated to correspond to each value. So a one year (12 month) moving average of temperature would be calculated by taking the average of the 12 months that end in January 2015, then the 12 months that end in December 2014, then November 2014, etc, going backwards in time.

In some ways this is a preferable measure than taking each year’s value. There are two reasons a 12 month moving average is good. First, it is 12 months long so the variation that happens across a year in surface temperature values is included in the average, so that relatively unimportant squiggling up and down of the data is dampened. Second, it lets us see the march of temperature change over time.

I used the NASA GISS data base, which just updated its value for January, to calculate a 12 month moving average for the entire record, which begins in 1880. January, as you will recall, was the second warmest January in the entire record. (For those keeping track, February of 2015 promises to be pretty warm too, and will without a doubt be warmer than February 2014, because that was an oddly cool month.) The temperature anomaly value for the last 12 months (up through January 2014) is about 68 (1/100ths of a degree C, the standard number) above the baseline used by NASA. That is the highest value ever for a 12 month period, so just as 2014 was the warmest year on record in that database, the last 12 months were also the warmest year (defined as a 12 month period) in that record.

Here’s the graph:
NASA-GISS_12_month_moving_average_surface_temperature_Jan_2015

There is nothing surprising here. Global warming is happening. We’ll continue to have many 12 month periods which are the warmest ever, along with the occasional 12 month period which is not, because the temperature squiggles up and down as it trends upward.

Also covered HERE.

Comments

  1. #1 Desertphile
    Santa Fe, New Mexico (yes, that's in the USA)
    February 17, 2015

    “… how does the last 12 months, ending at the end of January 2015….”

    A fine article, but are you saying there will be no more months here on Earth? Perhaps you mean “the previous 12 months,” but if not, I’m going to stop flossing my teeth—- why bother?

  2. #2 Greg Laden
    February 17, 2015

    Yes, the last months. Sorry you had to hear it here!

  3. #3 Ned
    February 17, 2015

    Nice. And you’re right to note that once February is recorded in GISTEMP, the 12 months ending with February will likely set a clear new record for 12-month average temperature, since last February was (relatively) cold and dropping it from the rolling average will lead to a clear increase.

    FWIW, by this metric the calendar year of 2014 is only tied for third place, after two 12-month periods in 2009/2010.

    Of course, none of this means much, in comparison to the overall multi-decadal upward climb of temperatures. These kinds of “records” are purely a curiosity.

  4. #4 Ned
    February 17, 2015

    Gah. Are those idiotic pictures next to our posts really necessary?

  5. #5 Greg Laden
    February 17, 2015

    I can change them to different idiotic pictures at will. But I don’t get to choose which idiotic picture you get. But, if you had one of those thingies you would have your own picture. Gravitar, maybe.

  6. #6 Ned
    February 17, 2015

    Thanks for the reply. The current version of the idiotic picture is less bad than previous one, though I don’t know whether that changes or whether others see the same version I see.

  7. #7 Craig Thomas
    February 17, 2015

    You should pick your own
    idiotic picture,
    like I have.

  8. #8 Chris O'Neill
    February 18, 2015

    In some ways this is a preferable measure than taking each year’s value.

    Another way is that the short term trend can sometimes tell you whether new 12-month records are very unlikely for a while or whether there is a good chance that new such records are likely in the near future.

    For example, there is currently a short term uptrend in the 12-month average which from past history makes it very likely that the near future will produce new records. When a downturn eventually occurs then it usually continues for at least a year so a new record is not likely for at least a year or two.

    http://www.woodfortrees.org/plot/gistemp/from:1974/mean:12/plot/none

  9. #9 Greg Laden
    February 18, 2015

    Yes, I’d love to work out the statistics of the up and down trends a bit better.

  10. #10 Desertphile
    Santa Fe, New Mexico (yes, that's in the USA)
    February 18, 2015

    You should pick your own
    idiotic picture,
    like I have.

    Unfortunately, we all end up with the face we deserve.

  11. #11 dean
    February 18, 2015

    “Unfortunately, we all end up with the face we deserve.”

    Says the man lucky enough to have a cool hat.

  12. […] in NASA’s database as the previous 12 months (February 2014–January 2015). This is using a 12-month moving average, so we can “see the march of temperature change over time,” rather than just once every […]

  13. […] in NASA’s database as the previous 12 months (February 2014–January 2015). This is using a 12-month moving average, so we can “see the march of temperature change over time,” rather than just once every […]

  14. #14 Chris
    Albany, NY
    February 20, 2015

    Can someone kindly explain to me how temperatures in the graph can go back to 1881? Have the locations of the measurements remained constant? Have the instruments used remained constant? Don’t we now look at ocean temperatures?

    I can’t find answers to at NASA or other web sites.

  15. #15 Greg Laden
    February 20, 2015

    Chris, good question. Hey, say hi to all my friends in Albany! (I was born and raised there). It really is true that if you go to the NOAA or NASA web site you’ll have a hard time finding these details.

    A few quick items then a link to something more detailed. First, we have ocean and surface temperatures going back to the 19th century, but the density of those measurements increases over time. Since some time in the 1970s, sea surface temperatures have been measured by satellite.

    The simple version of how to calculate global temperature is this. You gid out the globe. Then you find all the data you can in each grid square. If the data are good (enough, good quality) then you have a number. If there is a grid that has very little data, you have to figure out what to do. There are numerious ways to do this, including interpolation/extrapolation, etc. As you go back in time the degree to which you have to fill in or otherwise make reasonable each grid measurement increases, but there were (I think) big jumps in the quality of the data in the 1940s (because during war the weather becomes very important) after 1958 (huge funding in the geophysical year) and Sputnik (more science) and the 70s (better technology). Since the question of global warming needs good data from the middle of the 20th century, the curve is on pretty solid ground.

    Proxyindicators that overlap the more recent decades and older decades confirm that even though the quality of the data drops off, the curve is basically right.

    There is a huge amount of scientific literature on this. When you look at the original research, you find a lot of attention to error. There is a solid attempt to measure confidence limits, etc, as they change over time going into the past.

    For a detailed look at much of this, see: http://www.carbonbrief.org/blog/2015/01/explainer-how-do-scientists-measure-global-temperature/

  16. #16 Desertphile
    Santa Fe, New Mexico (yes, that's in the USA)
    February 20, 2015

    Can someone kindly explain to me how temperatures in the graph can go back to 1881?

    The instrument record goes back to at least the late 1600s in some regions of Earth (such as Central England), but as Greg Laden noted the surface area the {weather stations / temperature readings} cover was not dense enough to yield an adequate level of confidence to use for a global average.

    Plotting the likely global average mean temperatures starting in year 1880 still yields a large margin of error up to about year 1940, but 1880 is the date when density of temperature-recording stations everywhere except at the poles was considered adequate enough to derive a reasonable confidence in the averages.

    But what I just wrote could be completely wrong. I am not a scientist.

  17. #17 Brenda
    Arizona
    February 23, 2015

    Information can be adjusted to meet the needs of the author, but the underlying message remains: Earth’s climate is fluctuating across the lands. While climate scientist ring the alarm of climate change without deviation from this path.
    Despite all geo-climate data, people do not heed the warning “…that lands had been poisoned and future was imperiled to change their political climate, their security climate, economic climate, and spiritual climate” condenses Klein’s reading (Klien pp. 307-8). Is our climate for sale if so what is the price?
    Having recently read Naomi Klein, for assignment, this is my opinion. My people, the Navajo are victims of colonization, capitalism and now globalization, yet, we survive. We hold to our language, lands, traditions and venture out to gain higher educations to understand our past, present and future.
    Our history is colonization where our people experienced genocide, separation from land, family and language. Learning the lessons of the greediness of came in rivers of blood. The blood of our chéé’s (Grandparents) spills across our deserts calling for justice.
    Capitalism brought environmental and health atrocities. While Navajo lands remain rich in coal, water and uranium, capitalism is quick to claim and exploit the environment and people. Uranium mines continue to erode the environment and expose the Navajo people to long-term health concerns like cancers.
    Globalization, our future, introduces climate change not by Navajo hands but by governments who create competition for energy, food and water resources, and by creating regulations without considering damage to Mother Earth. Recently here in AZ we experienced forest fires, earthquakes, and droughts. These environmental wake up calls remind us that life is short and unpredictable despite science efforts. My place is to understanding climate change and then rally around the cause.
    “Crude that impoverishes us…impoverishes the world… (Klien pp. 370)” crosses borders creating new alliances such as the Cowboy and Indian alliance in Oregon. Residents, white and indigenous, stand side by side against environmental dangerous projects like the Keystone XL pipeline (Klien pp. 319). Alliance? Indigenous people know all too well the historical value of alliance. This leads me to ask: Will the alliance between today’s cowboys and Indians have equality? Will the dominate State (the United States of America and corporations) carry the beneficial weight while Indians carry the environmental and health atrocities as history reflects?
    In conclusion, people of Mother Earth need to heed climate change warnings and change the direction of the future of our grandchildren before all is lost.

  18. #18 Gary Hall
    February 28, 2015

    Note (not a new observation): there are two spurts of warming in the graphic (the record). The first one from around 1911 through 1944ish – all occurs prior to the consensus view of when CO2 had risen enough to force a measurable addition to what was occurring within nature.

    The second spurt of warming is enhanced by anthropogenic gases. Some say most – some say some – some say perhaps a little.

    All – all of it – seems mostly naturally occurring.

  19. #19 Greg Laden
    February 28, 2015

    It may look like that on the graphic but that is not really what happens. First, the ups and downs you see early in the 20th cen and late in the 19th cen. are mainly caused by factors other than CO2, but this is not “the first of two” warming spurts. This is simply long term variability that would look like waves across the sea if the graph was a few centuries long. So, you are cherry picking that.

    Second, there is no consensus that earlier warming totally lacks a CO2 signal. Please don’t come here and spew anti-scientific denialist crap and use the word “consensus” to support you view. That makes me sick.

    Third, there are piles of evidence that this is absolutely not naturally occurring even if it “seems” like it to you. You are simply wrong.

  20. #20 Gary H
    February 28, 2015

    Spewing?

    Did I say this? ” there is no consensus that earlier warming totally lacks a CO2 signal.”

    Totally? I think I said . . “consensus view of when CO2 had risen enough to force a measurable addition to what was occurring within nature.”

    The IPCC is rather firm on “1950.”

    In their most recent report, AR5, they repeatedly refer to having confidence of anthropogenic fingerprints on GW and other suspected climate change issues, since 1950.

    From NASA’s Global Climate Change – Consensus Page – http://climate.nasa.gov/scientific-consensus, where the summary statements of some 18 favorable to the ACC argument are posted, we find the following statements:

    American Geophysical Union – Humanity is the major influence on the global climate change observed over the past 50 years.

    American Meteorological Society – the dominant cause of the rapid change in climate of the past half century is human-induced

    The Geological Society of America – global climate has warmed and that human activities . . account for most of the warming since the “middle” 1900s.

    International academies: Joint statement – It is likely that most of the warming in recent decades can be attributed to human activities (IPCC 2001).” [recent decades certainly is not since “late 1800’s]

    U.S. Global Change Research Program – “The global warming of the past 50 years is due primarily to human-induced increases in heat-trapping gases.

    Intergovernmental Panel on Climate Change – “Most of the observed increase in global average temperatures since the mid-20th century is very likely* due to the observed increase in anthropogenic greenhouse gas concentrations.”

    Sorry for my spewing.. Goodness I put the option of using “spouting off instead.

    PS – I’d note that “your” graphic did not illustrate any “up’s” during the 19th century – only down.

    And on your final point – there is little to no evidence of this; simply tons of belief (be it scientific, or not). There is evidence that there was another warming spurt in the 2nd half of the 20th century – which paused in about 1998.

    I suspect that we’ll stay warm for a couple hundred more years – a little more – a little less; that would seem to be the naturally occurring cycle. Not likely to find out.

  21. #21 Chris O'Neill
    February 28, 2015

    prior to the consensus view of when CO2 had risen enough to force a measurable addition

    CO2 forcing from 1780 to 1941 = 0.15 doublngs

    CO2 forcing from 1941 to 1985 = 0.15 doublngs; IPCC formed 1988.

  22. #22 Greg Laden
    February 28, 2015

    Yes spewing. You did it twice.

    The graphic I used starts in 1880. The 19th century starts in 1800. Or, maybe, 1801, depending on which kind of pedant you are.

  23. #23 Chris O'Neill
    February 28, 2015

    Did I say this? ” there is no consensus that earlier warming totally lacks a CO2 signal.”

    Your previous claim was:

    All – all of it – seems mostly naturally occurring.

    Your previous claim assumes there is a consensus that earlier warming totally lacks a CO2 signal.

  24. #24 Astrostevo
    February 28, 2015

    @ 18. Gary Hall :

    I suggest -and request please – that you watch this clip by David Attenborough :

    https://www.youtube.com/watch?v=S9ob9WdbXx0

    ‘Sir David Attenborough: The Truth About Climate Change’ posted by Pauli Fabian which quickly and effectivley demolishes your claim.

    See also the more in-depth and also highly informative youtube clip here :

    https://www.youtube.com/watch?v=w5hs4KVeiAU&list=PL82yk73N8eoX-Xobr_TfHsWPfAIyI7VAP&index=5

    5. Climate Change — isn’t it natural?’ by
    potholer54 – his whole series is superb and well worth watching in full in my view.

    Or if you don’t like videoclips or your computer is so bad its even worse than mine and won’t actually play them check out here :

    http://www.skepticalscience.com/global-warming-natural-cycle.htm

    Among so many other places. (Eg. NASA’s website for one is a great source of real solid evidence here too as is the Bad Astronomy blog, the RealClimate website etc …)

    If you have seen those and still disagree then can you please explain why and provide extraordinary evidence to support your extraordinary claim here?

  25. #25 Astrostevo
    February 28, 2015

    @22. Greg Laden : ” The 19th century starts in 1800. Or, maybe, 1801, depending on which kind of pedant you are.”

    Maybe we should split the difference and say it starts in June 1800? 1800.5? 😉

  26. #26 Brainstorms
    March 1, 2015

    (Computer) scientists always start enumerations with zero…

  27. #27 Chris O'Neill
    March 13, 2015

    We just had the warmest “year” again

    And again: http://data.giss.nasa.gov/gistemp/tabledata_v3/GLB.Ts+dSST.txt

  28. […] record, which now makes March 2014–February 2015 the hottest 12 months on record. This is using a 12-month moving average, so we can “see the march of temperature change over time,” rather than just once every […]

  29. […] record, which now makes March 2014–February 2015 the hottest 12 months on record. This is using a 12-month moving average, so we can “see the march of temperature change over time,” rather than just once every […]

  30. […] record, which now makes March 2014–February 2015 the hottest 12 months on record. This is using a 12-month moving average, so we can “see the march of temperature change over time,” rather than just once every […]

  31. […] mild February means that the March 2014 to February 2015 period was the hottest 12 months on record, beating February 2014 to January 2015. This metric is considered to be more significant since it […]

  32. […] mild February means that the March 2014 to February 2015 period was the hottest 12 months on record, beating February 2014 to January 2015. This metric is considered to be more significant since it […]

  33. […] the warm February means that the period from March 2014–February 2015 beat the record set just last month for the warmest on 12 months on […]

  34. […] explain this sad and sobering news, no one puts it better than biological anthropologist Greg Laden: “There is nothing surprising here. Global warming is happening. We’ll continue to have many 12 […]

  35. […] which now makes March 2014–February 2015 the hottest 12 months on record. This is using a 12-month moving average, so we can ‘see the march of temperature change over time,’ rather than just once every […]

  36. […] is using a 12-month moving average (see above), so we can “see the march of temperature change over time,” rather than […]

  37. […] chart uses a 12-month moving average, so we can “see the march of temperature change over time,” rather than just once every […]

  38. #38 Jessica
    May 22, 2015

    It looks like moving average is a great way to track temperature!

  39. […] in NASA’s database as the previous 12 months (February 2015–January 2016). This is using a 12-month moving average, so we can “see the march of temperature change over time,” rather than just once every […]

  40. […] in NASA’s database as the previous 12 months (February 2015–January 2016). This is using a 12-month moving average, so we can “see the march of temperature change over time,” rather than just once every […]

  41. […] NASA data shows that the previous 12 months have also been the hottest 12-month period every recorded, using the space agency’s 12-month moving average. […]

  42. […] NASA data shows that the previous 12 months have also been the hottest 12-month period every recorded, using the space agency’s 12-month moving average. […]

  43. […] NASA data shows that the previous 12 months have also been the hottest 12-month period every recorded, using the space agency’s 12-month moving average. […]

  44. […] NASA data shows that the previous 12 months have also been the hottest 12-month period every recorded, using the space agency’s 12-month moving average. […]