Urban corrections in Gistemp (and GHCN-M), “then and now”

Further content coming soon. This placeholder post published now to allow a link to the coming post to be included in an online comment.

Hansen et al. 1999 (Hansen, J., R. Ruedy, J. Glascoe, and M. Sato, 1999: GISS analysis of surface temperature change. J. Geophys. Res., 104, 30997-31022, doi:10.1029/1999JD900835) illustrates the Gistemp urban adjustment with two examples, Tokyo and Phoenix.

Hansen1999Fig3

Hansen1999Fig3caption

This post first of all updates these two examples. First consider recent data, Gistemp up to September 2015 (the “now”). In all plots below the values in the key show the temperature rise, in degrees C per decade for the corresponding data set. Data series based on GHCN-M v2 (the “then”) are shown as dotted lines:

TokyoGISS

TokyoAdjustments

Most of the adjustment comes from the adjusted GHCN-M data now used by Gistemp as input. Gistemp itself makes a smaller contribution to the overall adjustment.

PhoenixGISS

PhoenixAdjustments

In this case GHCN-M adjusted and Gistemp contribute roughly equally to the overall adjustment.

The overall adjustment for Tokyo, 16 years on, is somewhat less that Hansen et al. 1999 had shown, although they suggested that “The true nonclimatic warming in Tokyo may be even somewhat larger than suggested by Figure 3”, while that for Phoenix is almost the same 16 years on.

Now consider an older Gistemp data set, with data up to March 2009 (date chosen as the archived data is conveniently to hand on disk). In this case Gistemp was still using the unadjusted GHCN-M data as input.

TokyoGISS200903

TokyoAdjustments200903

PhoenixGISS200903

PhoenixAdjustments200903

The broken-line Gistemp adjustments are seen more clearly here, since the inclusion of the GHCN-M adjustments on the earlier plot tends to obscure the broken-line nature of that Gistemp adjustment.

Finally consider both dates plotted together:

TokyoGISSboth

TokyoAdjustmentsboth

PhoenixGISSboth

PhoenixAdjustmentsboth

We see

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GHCN-M adjustment samples: (7xx) Antarctica

For details of what is illustrated here, start from Wanderings of a Marseille January 1978 temperature, according to GHCN-M, continue with GHCN-M: Stations similar to Marseille/Marignane

Further discussion to come later once images have been generated and added for remaining regions.

700 Antarctica (34)

As data for some of these stations comes from both GHCN-M and SCAR, Gistemp can have two different values in the same month. Values derived from SCAR data are distinguished by use of a filled black triangle symbol. Stations which have no adjustments and SCAR stations which do not appear in the GHCN-M inventory are not shown here.

SANAE
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GHCN-M adjustment samples: (6xx) Europe

For details of what is illustrated here, start from Wanderings of a Marseille January 1978 temperature, according to GHCN-M, continue with GHCN-M: Stations similar to Marseille/Marignane

Antarctic stations have been inserted here now before returning to continue with the GHCN-M station sequence. I may also split this post into two posts, Europe and Antarctica, later. I have also now added images for Irish stations. 

Further discussion to come later once images have been generated and added for remaining regions.

601 Albania (4)

Shkodra

602 Armenia (2)

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GHCN-M adjustment samples: (5xx) Pacific and Australasia

For details of what is illustrated here, start from Wanderings of a Marseille January 1978 temperature, according to GHCN-M, continue with GHCN-M: Stations similar to Marseille/Marignane

Further discussion to come later once images have been generated and added for remaining regions.

501 Australia (586)

Richmond
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GHCN-M adjustment samples: (4xx) Central and North America

For details of what is illustrated here, start from Wanderings of a Marseille January 1978 temperature, according to GHCN-M, continue with GHCN-M: Stations similar to Marseille/Marignane  Pairwise Homogenization may perform better in Canada and the United States of America. This is not unexpected − pairwise homogenization was benchmarked for the United States. (C. N. Williams, M. J. Menne, P. W. Thorne, Benchmarking the performance of pairwise homogenization of surface temperatures in the United States. J. Geophys. Res. 117 (D5), D05116 (2012). doi:10.1029/2011JD016761). Further discussion to come later once images have been generated and added for remaining regions.

Update: As I have started to archive USHCN data as well as GHCN-M data, an example of USHCN adjustment is also shown below for one station (Sacerton). Continue reading

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GHCN-M adjustment samples: (3xx) South America

For details of what is illustrated here, start from Wanderings of a Marseille January 1978 temperature, according to GHCN-M, continue with GHCN-M: Stations similar to Marseille/Marignane

301 Argentina (90)

LaQuiaca
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GHCN-M adjustment samples: (2xx) Asia

For details of what is illustrated here, start from Wanderings of a Marseille January 1978 temperature, according to GHCN-M, continue with GHCN-M: Stations similar to Marseille/Marignane

203 Bangladesh (23)

Chittagong

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