Dr. Gavin Schmidt, a lead researcher with NASA’s Goddard Institute for Space Studies (GISS) that does leading climate change studies, replied to one of my posts and made an assertion that the USHCN and GHCN stations and station data being discussed here in my blog are not used in validating climate models. This is surprising to me.
Here is the full correspondence:
Schmidt’s first post:
> Don’t let me get in the way of your efforts here, but please stop saying that “This data is in fact used in climate modeling to predict our climate future”.
>
> This is simply not so.
>
> You’ve downloaded the GISS model - perhaps you’d like to show me where these station data are used? You won’t be able to because they aren’t.
>
> Observational data at large scale (not individual stations) are used to evaluate the models after they’ve been run - but again generally only at the continental scale and above. The evaluation is not just with trends but
> with patterns of variability (El Nino responses, NAO etc.) and obviously, the better the data the more reliable the evaluation.
>
> Note that the climate model hindcasts for this area are around 0.5 over the 20th Century - significantly less than this individual station. Should this record therefore be shown to contaminated, it would actually improve our confidence in the models, not lessen it!
I responded to this on June 21st 2007 as follows:
> Gavin,
>
> I thank you for commenting on my blog, Watts Up with That? I’m honored
> that you would take the time. Rather than reply immediately, I thought
> I’d give some thought and research to my response, hence the delay. I
> also thought you’d appreciate a direct reply rather than a blog post.
>
> You wrote on the blog:
>
> “You’ve downloaded the GISS model - perhaps you’d like to show me where
> these station data are used? You won’t be able to because they aren’t.”
>
> I did some looking at a paper you authored, I found Schmidt et al 2006,
> from BAMS, which is also posted on your website:
> http://pubs.giss.nasa.gov/docs/2006/2006_Schmidt_etal_1.pdf
>
> You wrote on page 168 of the BAMS article:
>
> “We endeavor to compare the model simulations to as many suitable
> datasets as possible. … . Where useful gridded datasets exist of
> selected in situ data we use those.”
>
> After reading through your paper, I agree that you did not show any
> comparisons to GISS gridded data and I will withdraw any implication
> that you used GISS station data. However, I must say that I’m surprised
> to learn that GISS gridded data did not meet the standards of Schmidt et
> al 2006 of being either “useful” or “suitable”. Thank you for drawing
> this to my attention.
>
> However, later in the article, on page 176, you show comparisons of
> model output to CRU surface temperature data on two occasions:
>
> “Surface air temperatures (SATs; Fig. 17) show a general warm
> continental bias in comparison to the updated Climate Research Unit
> (CRU) data (Jones et al. 1999).
>
> Figure 23 on page 187 shows Taylor diagram comparisons among the
> selected models for the December-February (DJF) and June-July (JJA)
> extratropical NH CRU surface air temperature (SAT)”
>
> It is my understanding that CRU uses GHCN station data, which includes
> the USHCN sites discussed here in my blog. So, my answer to your
> question is that Figures 17 and 23 of Schmidt 2006 et al use the station
> data discussed here via the CRU gridded data. It has always been my
> understanding that adjusted GHCN and USHCN surface station data (also
> listed on the GISS webpage) including the ones I show plots of, is
> applied to a gridded data scheme for use in the computer models, such as
> model E. If I am in error in that assumption, I welcome you pointing out
> that error.
>
> If you felt that I was speaking of a specific station data being “used
> to predict our climate future” that of course is not my intent. If that
> was the case, I’ll revise the wording to make it clearer.
>
> Regarding your mention that “contamination of station data would improve
> your confidence in your model”, I must say that I’m a bit surprised at
> this. I’m not really in a position to dispute this yet, but would
> appreciate some additional clarification as why you are so certain of
> this without even seeing the impact of contaminated data. I surmise the
> opposite to be true, but I welcome further understanding.
>
> Again I thank you for your comments, and I welcome any correspondence or
> suggestions you may have.
>
> Best regards,
> Anthony Watts
Dr. Gavin Schmidt replied on June 22nd, 2007 with:
My comments stand. The station data are not used *in* climate models, and
they are not used to predict future climate. So yes, the sentence you have
is just wrong. I’m not sure how you could edit it to make it correct.
We compare the models to the gridded products that deal with individual
station problems as best they can. We have used the GISTEMP and CRU
products to do so. (Semantic note, ‘compare to’ is not the same as
‘include in’). For the specific station you have highlighted, the grid
point trends in the products (~0.5 deg - eveballing it, since I’m on
travel) are significantly less than the trend you show (2 deg or so).
Climate model results for the 20th C are similar (i.e. 0.5 deg). Thus
reductions of the trend at this station would actually improve the match
to the model - always being clear that you shouldn’t really compare
model grid boxes to individual stations…
If you are of the opinion that this station is contaminated, then you have
to admit that the process designed to remove artefacts in the GISS or CRU
products has in fact done so - (i.e. that grid box in the product does not
have a 2 deg/Century trend).
Improvements to that process and the data are always welcome, but do not
ascribe consequences to your project that clearly do not follow.
Gavin
*——————————————————————–*
| Gavin Schmidt NASA/Goddard Institute for Space Studies |
| 2880 Broadway |
| Tel: (212) xxx-xxxx New York, NY 10025 |
…| |
*——————————————————————–*
[email address and tel# removed by Anthony for privacy/spam purposes]
So one has to wonder.
If Dr. Schmidt’s point is only the observation that they do not reconcile their models with every individual station (as opposed to gridcell composites calculated by GISS and CRU), then there is no misunderstanding.
However, it is very clear that the NASA GISS and CRU (Climate Research Unit) use this station data in arriving at their gridcell values which are what is presumably used in testing the models. From 53 USHCN site surveys done so far we know that a number of stations do not meet published WMO (World Meteorological or NOAA (National Oceanic and Atmospheric Administration published standards.
There is no evidence at present that NASA GISS or CRU have made any effort to verify quality control standards at these USHCN stations. Whether these quality control issues will have a significant impact on overall averages remains to be seen. The only way to tell for certain is by examining individual stations though the site survey process as is being done on www.surfacestations.org and then doing an assessment of how pervasive the quality control problems are and what the potential impact of these problems may be.
But, any problems in individual USHCN stations will affect gridcell values. For non meteorologists, a gridcell is a box on a map that has been divided up into a x-y lines and specific data applied to each box. This helps in computer modeling because with computer programs it is easier to divide into cells, then calculate and display. Below is an example map that may help you visualize gridcells:
Whether it’s a big problem or a little problem remains to be seen, but it’s odd for Dr. Schmidt to pretend that it’s not a problem because they use the gridded version of the data.
Recent Comments