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European reanalysis of temperature confirms record warmth in 2010

Posted on 13 September 2010 by John Cook

The European Centre for Medium-Range Weather Forecasts (ECMWF) have recently released an update of their reanalysis temperature record. This record is a construction of surface temperature utilizing a range of sources including surface temperature measurements, satellite data, radiosondes, ships and buoys. The new results find that the average temperature over land areas of the extratropical northern hemisphere reached a new high in July 2010.

Figure 1: Anomalies in the mean two-metre temperature for May, June and July (deg C), averaged over all land areas north of 20N. Anomalies are relative to the period 1989-2001.

Probably of more interest to most is the global temperature record. The advantage of the ECMWF is it utilises it's variety of data sources to pull together a global record of surface temperature. This enables them to include regions such as the Arctic where warming is most pronounced. The global average over the 12 months to June 2010 ranks as the second highest on record, insignificantly smaller than the average for the calendar year of 2005.

Figure 2: 12-month running average of global-mean two-metre temperature anomalies (K) relative to the period 1989-2001. Shading is used to indicate an uncertainty range of ±0.1K.

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Comments 1 to 28:

  1. John, you left all the meaty bits out of the press release.

    "Temperature anomalies vary from one year to the next because of the natural dynamical variability of the climate system"

    "The global anomaly declines slightly in the very latest 12-month average, due to a recent shift toward La Nina conditions in the tropical Pacific and relatively low temperatures over tropical and southern hemispheric land areas, which offset last month’s high northern hemispheric temperatures."
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    Response: I would've thought the year-to-year variability was pretty obvious from Figure 2 :-)
  2. I'd just come here from a skeptics site, and was trying to make sense of the title, "European reanalysis confirm record warmth". For a second there I thought it was going to be an article about how warm the Medieval Warm Period really was!
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    Response: Once I'd finished the article, I tweeted it and thought, well, that title doesn't make much sense, so I fleshed out the tweet with "European reanalysis of global temperature confirms record warmth in 2010". Thought about retitling my blog post with a more clear headline, decided against it mainly due to laziness. Will do the job properly now...
  3. This will be a great resource. I wish they would do this every year... or at least combine with hadley...
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  4. Another note for John,
    We should consider revising the 1998 is the warmest on record in light of this new result...
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  5. Wow, record warmth? This is just the warmest lately.
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  6. These temps are almost as far above normal as they were below normal not that long ago. I guess they are just averaging things out.
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  7. cruzn246 - its an anomaly plot. The temperatures are shown wrt to average for 1989-2001. This is an arbitrary level, not "normal". If temperatures are trending up, then anomaly plots based on average of mid-temp will show left down and right up. Its "averaging out", it is trending up.
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  8. “or at least combine with hadley...”

    - if You please ...

    with ‘Global and European temperature (CSI 012) - Assessment published Jun 2010’

    Here it looks a little "interesting", right? Especially before the year 1970 ...
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  9. I'm struggling with anomaly graphs in the above formats. I undestand the ones that NOAA produce - the one with the world map covered in blue and red dots.

    Could someone walk me through the above if if you were talking to a child please!!
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  10. Johngee - It's a plot of the difference between the calculated global average and an average of those temperatures recorded from 1989 to 2001 (if you look at the 'area under the graph' for that period it will average out at 0.0 anomaly). It's showing how the calculated global temperature has changed with respect to that period. The period chosen is arbitrary, though it helps to use the same comparison period as everyone else to make comparisons easier.
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  11. cruzn24,
    As you can see from the above graph, the temperatures never were below the average from 1989-2001. The recent cold was localized in area and not that cold. Most of the world was hot last Dec-Jan-Feb while the cold areas were genreally the USA and parts of northern Europe. It is a denier fantasy that it was cold last winter. The data does not support that fantasy.
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  12. Last (NH) winter was the warmest on record (average global temp)
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  13. Re: Johngee (9)

    Figure 1 is for land areas north of 20 degrees north for May-June only. Figure 2 is for combined global land + sea areas.

    Both use a baseline of 1989-2001 and use anomalies instead of temperatures to reduce weather-related noise in the data. Both are surface-layer (2-meter) data instead of something like satellite-obtained data, which can also measure various layers of the atmosphere (the Earth's atmosphere is layered like an onion; because of this, it heats and cools differentially. The addition of CO2 essentially causes a differential accumulation of heat in the lower layers by slowing the transfer of heat to upper layers. Hence stratospheric cooling and tropospheric heating).

    Figure 1 shows that, in the 40 years of data shown, land temps away from the tropics have warmed in the last 10 years relative to the other 30 years of data.

    Figure 2 shows that global (land + sea) temps have been rising fairly linearly across the entire range of the data (if you were to put a ruler on the graph and draw a straight line through the midpoint of each year of the data, you'd get a line rising from the left side of the figure to the right side. This line is said to have a positive slope, showing the upward overall "trend" of temperatures in the data).

    Both figures show an essentially noisy dataset (even using anomalies to reduce the noise), but one in which a clear signal can be seen.

    It's getting hotter. And there is no indication of slowing in the rise of temperatures.

    Hope that's more clear! If you have more questions, let me know.

    The Yooper
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  14. Where are the plots for global heat content anomaly and global dew point anomaly?
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  15. I dont want to be pedantic but focussing on the extratropical northern hemisphere largely increase the global warming signal compare to a true world average temperature.
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  16. Arkadiusz - The "Rate of change" graph is interesting, although I always find it confusing to look at a derivative (rate of change) chart right after an anomaly (total change) chart.

    I prefer total change as more useful for state (how far we've gone), but derivative rate charts as more useful for examining any underlying process changes.
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  17. Yvan @15,

    Look at the second graph-- that is for the globe (a true global temperature, unlike the SAT data and even the MSU data). A clear warming pattern is evident. This is an estimate from looking at the graph, but for the period 1970-2010 the mean rate of warming I get is about 0.17 C/decade. Pity that ECMWF don't provide the mean rate of warming and/or actual numbers (then again, I have not undertaken a thorough search).

    TOP @14, ECMWF also have plot of Td (dew-point temperatures) available on their web-site, requires a little digging though.
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  18. 11.michael sweet

    You can investigate the ERA-Interim reanalysis using this tool.

    It shows for NH winter (DJF) that, as you say, NH mid-latitudes (30N-60N) were below normal. But actually quite cold, -0.4oC below average. SH mid-latitudes were fairly ordinary, +0.1oC. The two polar regions and the tropics were hot at +0.4oC to +0.6oC above average.
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  19. 17.Albatross

    The graphs in this article are actually data from ERA-40 and ERA-Interim fused together. Which seems strange? You can get the data for each of those from the link in #17.

    The trend for ERA-Interim (1989-2010) is 0.168 C/decade. Good guess!
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  20. Hi HR,

    Thanks, yes I got lucky there with my back-of-the-envelope estimate for the trend.

    Yes, they are fused, you can compare their data online using an interactive plotting too. What is interesting is that the ERA-40 seems to have been slightly warmer than the newer ERA-interim, which is anything would have reduced the warming trend.

    I cannot speak to how they spliced the data together, you would have to chat to them about that.
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  21. KR
    All you're seeing in the pre-1970s graph is essentially the changes due to the AMO....
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  22. Arkadiusz Semczyszak,
    It does look interesting...especially to see the change in the climate regime since the 1970s. Thank you for pointing this out. It clearly shows the dominance of natural forcings such as the AMO (which fits this almost perfectly) prior to 1970 and the dominance of the anthropogenic signal post 1970 with the consistent warming.
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  23. Humanity Rules:
    Here is the temperature map for J-F-M from the NCDC:

    While Siberia has large cold areas, the USA is not that cold. Canada is hot and evens out Siberia. The majority of the world is hot or warm. The temperature anomaly was 0.66C, the fourth highest on record. Fourth highest out of 130. For me that is a hot period. It just happened that the cool areas were the USA and Europe. By contrast, this summer has been RECORD heat in many areas.
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  24. Albatross,

    that's a great tool thanks.

    this is probably off topic but they show a recent warming trend after the latest volcanic activity in the stratosphere (clearer in the bottom graph). Does that matter?

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  25. HR,

    No worries. Re the temperatures in the lower stratosphere. Those data seem at odds with the long-term trend in the RSS data. Not sure what is going on there.

    That said, RSS tend from circa 1995 is pretty flat...a response to the recovery of ozone perhaps?
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  26. @ Daniel Bailey
    Me again! I've copied bits of your explanation with extra questions...

    'Both use a baseline of 1989-2001...'

    Is this baseline an average temperature for this period? If not, how is this baseline calculated?

    '...and use anomalies instead of temperatures...'

    Hang on, what is an anomaly if it isn't a temperature. Is an anomaly a temperature above or below the baseline reference? If not how is an anomaly classified?

    ' reduce weather-related noise in the data. Both are surface-layer (2-meter)...'

    You mean ground surface temperature readings by this?

    'Figure 1 shows that, in the 40 years of data shown, land temps away from the tropics have warmed in the last 10 years relative to the other 30 years of data.'

    Yep I see that. I also see that a line of best fit would show a warming trend for the 40 year period. Can anybody explain the apparent dramatic shift 10-15 years ago? Or can I not read the graph in this manner?

    'Johngee - It's a plot of the difference between the calculated global average and an average of those temperatures recorded from 1989 to 2001'

    Is that kind of what I'm saying above or am I way off?

    '(if you look at the 'area under the graph' for that period it will average out at 0.0 anomaly). It's showing how the calculated global temperature has changed with respect to that period. The period chosen is arbitrary, though it helps to use the same comparison period as everyone else to make comparisons easier.'

    Woa there... my calculus is good enough only to regognise that's what your talking about!! The big C is my next mathematical mission... should I choose to accept it :o)
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  27. Re: Johngee (26)

    In order to measure change, you must first start with a baseline. Otherwise, you have no frame of reference and thus cannot measure anything ("Dude, you're lost").

    With temperature change this starts with establishing the baseline. In Figure 1, all land surface temperatures for the months of May-July north of 20 degrees were calculated to get an average for the years 1989-2001. The change from this established baseline is called the "anomaly". Anomalies can be positive (evidence of warming) or negative (evidence of cooling). A common convention on temperature trend charts is to express positive anomalies in red and negative ones in blue.

    Anomalies are used because it is then possible to compare widely diverse and separated areas (not fair to compare absolute summer temperatures in Atlanta, Georgia to those in Nome, Alaska). And to reduce noise in the data, increasing the accuracy.

    Temperatures are typically taken at about the 2-meter level, for a couple of reasons:
    1. Keeping sensitive instrument packages off the ground keeps them from getting stepped on
    2. Ground releases temps more quickly than air; so by removing the gauges off the ground you minimize warming bias
    3. Gauges are easier to maintain and service at eye level than when on the ground (just seeing if you're still with me)
    Hmm, what else?
    "Can anybody explain the apparent dramatic shift 10-15 years ago? Or can I not read the graph in this manner?"
    You must be referring to figure 1. Note the baseline is reflected as the 0 horizontal line on the graph. The blue areas below the zero line are from a time period when it was cooler than the baseline period. Red areas above the baseline are from a period when it was warmer than the baseline. Applying a line of best-fit to the totality of the graph (blue and red) shows the overall warming. Where that line crosses the zero line (i.e., breaks the surface) does not imply that temperatures dramatically shifted in any way (yes, it would be a mistake to interpret the graph in that fashion...use all the data).

    So, both graphs show consistent warming, with no decline at all evident in the overall trend (even in the last 10 years, counter to what "some" may say.

    The land area reflected in Figure 1 contains the majority of the non-tropic land area of the globe; and its where most people live. Daytime air temps, while setting many record highs, can only warm just so far. The real increase in temperatures shown in Figure 1 come from higher average nighttime temperatures, reducing the temperature variance range between highs and lows, increasing average temps and increasing overall anomalies from baselines.

    Temperature increases are greatest towards the poles (look up "Polar Amplification" sometime), where the coolest air offers the greatest room for change.

    Figure 2 is more interesting. By using a 12-month average, seasonal variability is removed. Since it's global (land and ocean combined), one can see that the cherry-picking of "North America is cooling" is exposed as the charade it is. The most interesting thing about Figure 2 is not immediately obvious. About 93% of the warming of the globe has occurred in the oceans. Yes, the land has warmed too, but the oceans (with their huge thermal inertial mass) dominate the global climate. The warming going into the oceans goes two places:
    1. Transported to higher latitudes where the extra heat gets released into the colder air, warming the Arctic (one source of polar amplification) and melting the ice there
    2. Through the mixing layer into the deep ocean (temporarily sequestering it...this comes back later to bite our descendants in the a**, but that's a later story)
    Warming is largely driven (in the absence of any change in warming inputs from the sun since 1970) by our greenhouse gases (of which CO2 is the control knob) not being in equilibrium with energy inputs. GHG gases slow the rate of heat release at the top of the atmosphere (primarily the troposphere; this also explains the observed stratospheric cooling). As long as there is a net gain in atmospheric CO2 concentrations, continued warming is inevitable (as reflected in the Mauna Loa CO2 trend data).

    The warming is predicted by GHG theory, multiple converging lines of evidence (not just temperatures and anomalies) shows it's there and the stratosphere is cooling: as predicted as well. And without the warming from greenhouse gases, there would literally be no liquid water anywhere on the planet, and thus, no life. Perhaps on certain blogs...

    And, due to the thermal inertia of the oceans, even if CO2 releases by man were immediately reduced to zero and kept there for 30 years, the warming would still continue. And that's just due to the slow feedbacks. There exist longer ones which are still to come.

    Hope that helps (and doesn't depress the he** out of you like it does me),

    The Yooper
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  28. Global Temperature Anomaly Map - August 2010
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