RealClimate logo


Technical Note: Sorry for the recent unanticipated down-time, we had to perform some necessary updates. Please let us know if you have any problems.

Exploring CRUTEM4 with Google Earth

Filed under: — group @ 4 February 2014

Guest commentary by Tim Osborn and Phil Jones

The Climatic Research Unit (CRU) land surface air temperature data set, CRUTEM4, can now be explored using Google Earth. Access is via this portal together with instructions for using it (though it is quite intuitive).

We have published a short paper in Earth System Science Data (Osborn and Jones, 2014) to describe this new approach.

This is part of ongoing efforts to make our climate data as accessible and transparent as possible. The CRUTEM4 dataset is already freely available via the CRU and UK Met Office, including the full underlying database of weather station data. But accessing it through Google Earth will enhance:

  1. Traceability of how we construct the dataset, by showing the weather station data used to make each grid box temperature anomaly.
  2. Accessibility for teaching and research, by extracting grid box and weather station data without the need for programming.
  3. Identifying errors.  With ~6000 station records collected and collated by third parties there are bound to be errors.  If they are identified, they can be corrected. Note that the global temperature record is not greatly affected by changes to the input data (e.g. Figure 5 of Jones et al., 2012).

A walkthrough

The view when the KML file is first opened, with red/green shading to show grid boxes with CRUTEM4 data:

Navigate to a region of interest and click a shaded box to see the grid-box annual temperature anomaly:

Choose from links to view a larger annual image, a seasonal image, the grid-box data values (in CSV format for import into a spreadsheet) or choose “stations” to see the weather stations used:

Click a weather station pin to view the station annual temperature series, with links to larger annual and seasonal images, and to the station data values (again in CSV format for easy import into a spreadsheet):

We encourage you to try it for yourself – and to also read the open-access paper (Osborn and Jones, 2014) which describes the construction of CRUTEM4 in detail.

[Editor's note: Other portals for visualizations of station data exist from David Archer, GISTEMP and many National Weather Service websites.]


References

  1. T.J. Osborn, and P.D. Jones, "The CRUTEM4 land-surface air temperature data set: construction, previous versions and dissemination via Google Earth", Earth System Science Data, vol. 6, pp. 61-68, 2014. http://dx.doi.org/10.5194/essd-6-61-2014
  2. P.D. Jones, D.H. Lister, T.J. Osborn, C. Harpham, M. Salmon, and C.P. Morice, "Hemispheric and large-scale land-surface air temperature variations: An extensive revision and an update to 2010", J. Geophys. Res., vol. 117, 2012. http://dx.doi.org/10.1029/2011JD017139

13 Responses to “Exploring CRUTEM4 with Google Earth”

  1. 1
    tamino says:

    In stark contrast to how deniers portray the situation, the level of openness and even ease of use regarding global temperature data is impressive. You (and the NASA GISS folks and David Archer and others as well) are to be commended.

  2. 2

    Fantastic! Although I’ve done a fair amount of looking at the various data sets, even drilling down to station level on occasion, this is much easier than anything I was aware of previously. What a fun tool! Congratulations to the team who put this together.

  3. 3
    E. says:

    I take it no one who worked on this had a problem seeing red and green…

  4. 4
    Tim Osborn says:

    @E. (red/green).

    Good point. I did try a range of options but with the underlying ocean and land colours it wasn’t easy. There is no meaning to the red/green other than to make a chequerboard to show where the grid boxes are.

    If you save the .kml file, open in a text editor, you’ll see the definition of these colours is in the first segment of KML, lines 8 and 17. Feel free to edit this, save it and re-open in Google Earth.

    As it currently stands, “grideven” boxes are <color>#804444ff</color> and “gridodd” boxes are <color>#8044ff44</color>

    The first two hex digits are the transparency, then its blue-green-red. See:
    https://developers.google.com/kml/documentation/kmlreference#color

    I’ll find some colours that avoid this and post an alternative KML file soon.

  5. 5
    Slioch says:

    #E The page http://www.cru.uea.ac.uk/cru/data/crutem/ge/ states, “To avoid red/green colour problems, try this version with a grey checkerboard: CRUTEM4-2013-03_gridboxes_grey.kml”

  6. 6
    Tim Osborn says:

    @Slioch: yes, I added that after E’s earlier comment.

  7. 7
    Ron Manley says:

    An excellent initiative.

    As UEA acknowledge in their “Notes (Questions and Answers)” the next step is to improve the accuracy of reporting of station locations. 0.1 degrees is around 11 km at the tropics. Stations which were originally reported as rural could now be urban.

  8. 8
    patrick says:

    #7 That’s an interpretation. What the note says is:

    “A. The information we currently have about the latitude/longitude of each station is limited to 1 decimal place, so the station markers could be a few kilometres from the actual location. This is adequate for the construction of the CRUTEM gridded and global temperature records, because they do not depend on the precise location of each station. WMO/GCOS have asked member states to provide more accurate location details in future initiatives.”

    http://www.cru.uea.ac.uk/cru/data/crutem/ge/

    For short: “This is adequate for the construction of the CRUTEM gridded and global temperature records, because they do not depend on the precise location of each station.”

    Tamino at the top: “In stark contrast to how deniers portray the situation, the level of openness and even ease of use regarding global temperature data is impressive.”

  9. 9
    rocketeer says:

    Wow, this is fun. Even pictures of the stations. Here is my favorite:

    http://www.panoramio.com/photo/64988888?source=wapi&referrer=kh.google.com

  10. 10
    Barnet says:

    Hi,
    I tried “Exploring CRUTEM4 with Google Earth”.
    But now I would like to know how to suppress this display (because it’s perturb the normal view on Google Earth)

  11. 11

    This is an excellent move! To make it complete there still is a final layer of details missing: the raw unhomogenised station data. The station data currently provided are in some cases reconstructions pushing the start date of the station back using data from other stations which may even belong in other grid boxes.

  12. 12
    Clive Best says:

    Please also check out

    http://clivebest.com/world/Map-data.html

    There are 3 station time period selections – top right. Drag a rectangle to zoom in. Click on a red station dot to view the full time series.

    Google earth is great but it can also confuse IMHO.

  13. 13
    caerbannog says:

    Folks who are in the mood to play around with temperature data might want to download and experiment with the package at: http://tinyurl.com/NASA-HANSEN4

    It’s not a very polished app, but it is reasonably easy to set up and use. It’s also a bit of a big download @500MB, but if you have a decent Internet connection, you should be able to download it all in just a few minutes.

    The app allows you to compute global-temperature estimates with your own “custom” selection of GHCN temperature stations and then directly compare your own results with the official NASA “meteorological stations” index (via a simple GnuPlot display).

    You can select groups of stations based on rural/urban status, data record length, etc., or pick individual stations from a Google map browser front-end.

    The app displays results for raw and adjusted GHCN data right alongside the official NASA results. The algorithm the app uses is a very “dumbed down” gridding/averaging routine — dumbed down enough, in fact, that it could be taught to first-year programming students. Even so, it produces global-average temperature results that are remarkably similar to the published NASA results.

    The app consists of a “VirtualBox” virtual-machine appliance file with all software and temperature data in a preconfigured bundle. It will run on any newer (5 years old or less) Windows or Mac PC/laptop with at least 2GB memory.

    “Quickstart” instructions are provided on the right side of the download page. (The “quickstart” procedure boils down to: Download/install VirtualBox from http://VirtualBox.org, import the app appliance file into VirtualBox, and then hit the VirtualBox “Start” button.)

    I put the app together in an attempt to make it as easy as possible for others to see for themselves how incredibly robust the global temperature record is, and to be able to debunk the main “skeptic” claims about the global temperature record (i.e claims about UHI, “data manipulation”, “dropped stations”, etc.)

    One interesting thing to try:

    Compare the “Airport” vs “Not Airport” station results. What you will find is that much of the “bias” between raw and adjusted results disappears when you process only “Not Airport” stations.

    The reason for this is a number of stations currently at airports started their lives located in city centers. During the mid-20th century, those stations were moved from city centers to (cooler) outlying airport locations.

    As a result, the early temperatures for those stations were “biased high” (homogenization removes those station-move effects). Exclude those airport stations (easy to do with the station-selector control panel), and you will see much of that early “high bias” disappear from the raw temperature record.


Switch to our mobile site