No US temperatures

Along with other changes I’ve been making to ccc-gistemp I recently added a feature to remove GHCN stations that are in the contiguous US. I did that partly because GISTEMP’s Fortran has a similar feature, and partly because it allows me to do the following whimsical experiment:

Running ccc-gistemp with no USHCN data and dropping contiguous US stations from GHCN:

tool/run.py -p 'retain_contiguous_US=False;data_sources=ghcn,scar,hohenpeissenberg'

The -p allows a parameter from parameters.py to be set, without editing that file. retain_contiguous_US and data_sources are recently added parameters.

Onto the graphs!

Global:

Hmm, not much difference.

What about removing the ocean? Removing it should bring the differences due to land stations into sharper focus:

Tiny differences, not easily distinguishable from rounding.

What about zooming into the Northern Hemisphere, where the US is located?

Aha, some slightly less tiny differences appear which are not due to rounding. US citizens may be interested to note that their contribution to the recent trend is to lower it by a tiny amount (the trend is lower when US stations are included).

ccc-gistemp produces zonal anomaly files (because GISTEMP does). I’ve not really looked at them much before, but we can zoom in further on Zone 24N to 44N where most of the contiguous US is found. Note I had to rescale the next chart to fit the higher peaks in:

What above the next (GISTEMP) zone north, which includes the remaining part of the contiguous US but which has a slightly less dense station network and more volatile temperature swings:

The differences are all lost in the noise?

The US is only about 1½ percent of the Earth’s surface after all.

5 Responses to “No US temperatures”

  1. steven mosher Says:

    david,

    I left you a comment about the land masks.

    The url is to a land mask that contains inland water.

    You probably want a land/ocean mask ( where inland water is treated as land )

    url_LandOceanMask<-"http://islscp2.sesda.com/ISLSCP2_1/data/ancillary/land_water_masks_xdeg/land_ocean_masks_xdeg.zip&quot;

    The difference is not much, but I will be making the switch in my next release.

    if you have any questions about the difference and why a land/ocean is more suitable than a land/water ( water is ALL water including inland ) then ask.

    Perhaps there is a third database of inland water temps ( or marine temps ) and then you would want a land/water mask

  2. drj Says:

    Yup, got that mask thanks. And thanks for this note about land/water versus land/ocean. For my purposes I’m pretty sure I don’t care, but other people might. I’ve just written a post about how negligible the contig US is, do you think I’m going to start worrying about some petty lakes? :)

    I see water monitoring stations all over the plane when I’m out. I bet river authorities and utility companies measure water body temps all the time. Good pet project for an aspiring limnologist.

  3. bob Says:

    I am surprised at the second graph, I thought ocean and land were sufficiently different that a larger difference should show up comparing land with land+ocean

  4. bob Says:

    nevermind my mistake the graph makes complete sense afterall. I made a mistake and thought the graph was comparing land with land+ocean, rather than comparing land global vs land global minus US.

  5. drj Says:

    @bob: right. There are quite a lot of graphs and it’s not particularly clear what’s going on, but you seem to have worked it out. You’re right, I don’t compare land versus land+ocean in any graph on this page; the only difference is whether US data is included or excluded.

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