By Steve Goddard
In recent articles, I have have been discussing GISS’ claim that their divergence from Had-Crut over the last decade is due to better Arctic coverage.
They use the two images below to justify their claims.
The GISS 2005 image is deceptive, because GISS uses 1200km smoothing. Their actual 2005 Arctic coverage (using 250km smoothing) is below, and shows that they have very little data north of 75 degrees.
In order to make it easy to visualize the differences in coverage between GISS and Had-Crut, I mapped them onto 3D spheres, which eliminates the infinite distortion near the poles in this favorite GISS projection. I also threw in a recent NASA/NOAA/UAH equivalent map. None of these images have been cropped.
The images were created by taking the maps, replacing the gray areas which “signify missing data” with black, scaling the images to 512×512, and mapping them on to an OpenGL sphere. Assuming that the original maps all reach 90N at their top, the images are an accurate representation of their coverage. That probably is not exactly correct, but is close. It appears from the NOAA/UAH map geography that they have coverage further north than 82.5°.
Conclusion: GISS claims of better 2005 Arctic coverage in their recent paper are not justified.
UPDATE: Steve has rendered this video for further discussion.