I’ve moved to WordPress: http://bobtisdale.wordpress.com/

Wednesday, May 19, 2010

Tom Karl’s Trends Are Wrong - At Least in Slide 21

I’ve moved to WordPress.  This post can now be found at Tom Karl’s Trends Are Wrong – At Least in Slide 21
Correction: I have been advised that my Figure 4 in this post could be considered misleading because the trends intersect at 1900 and not toward the middle of the plot. The following illustration is a correction. It still shows, however, that the differences between two trends of 0.83 and 0.91 deg C/Century should be visible. (Thanks, Basil.)

Correction To Figure 4

A number of bloggers on the WattsUpWithThat thread “Tom Karl’s Senate Dog & Pony Show – it’s worse than we thought, again” noted the curious errors in the trend lines in Tom Karl’s presentation to Senate. The one that stood out for me was slide 21, presented here as Figure 1. It showed the global land surface temperature anomalies and linear trends for the new (Version 3) versus existing (Version 2) Global Historical Climatology Network (GHCN) dataset.
Figure 1

First Observation: The slide title states the data is monthly, but the data illustrated are annual averages. Figure 2 is a graph of monthly Global Land Surface Temperature anomalies presented by the NCDC from January 1900 to April 2010. Monthly global land surface temperature anomaly data should look like that, with lots of month-to-month variation.
Figure 2

Second, there are two linear trends listed on the Karl slide. Version 2 is noted to have a linear trend of 0.83 deg C/Century, while Version 3 is claimed to have a linear trend of 0.91 deg C/Century. But the trend lines are nearly identical and they present linear trends of approximately 0.75 deg C/Century, Figure 3. The trend lines are erroneous or the values listed for the trends are wrong.
Figure 3

Trend lines of 0.83 and 0.91 deg C/Century should be noticeably different, as shown in Figure 4.
Figure 4

And for reference, the NCDC’s Monthly Global Land Surface Temperature anomaly data, Figure 5, has a linear trend of 0.78 deg C/Century.
Figure 5

And the the NCDC’s Annual Global Land Surface Temperature anomaly data, Figure 6, has a linear trend of 0.77 deg C/Century.
Figure 6

Makes one wonder. If a simple comparison graph with linear trends is so error filled…

Tom Karl’s Powerpoint Presentation is available here:

A full-sized copy of Slide 21 is here:

The NCDC Land surface temperature anomaly data is available through the KNMI Climate Explorer:

1 comment:

RACookPE1978 said...

Thank you.

Clear and precise.


Tips are now being accepted.

Comment Policy, SST Posts, and Notes

Comments that are political in nature or that have nothing to do with the post will be deleted.
The Smith and Reynolds SST Posts DOES NOT LIST ALL SST POSTS. I stopped using ERSST.v2 data for SST when NOAA deleted it from NOMADS early in 2009.

Please use the search feature in the upper left-hand corner of the page for posts on specific subjects.
NOTE: I’ve discovered that some of the links to older posts provide blank pages. While it’s possible to access that post by scrolling through the history, that’s time consuming. There’s a quick fix for the problem, so if you run into an absent post, please advise me. Thanks.
If you use the graphs, please cite or link to the address of the blog post or this website.