Comments on: NASA Follows CA Recommendation

By: MarkW

MarkW — Fri, 07 Mar 2008 11:16:33 +0000

Any algorithm that iterates is going to accumulate rounding errors quickly.

By: Pat Keating

Pat Keating — Thu, 06 Mar 2008 23:04:07 +0000

If you are getting significantly different numbers in going from 32 bits to 64 bits, then you need to take a hard look at your algorithm, and use a different approach.

By: MarkW

MarkW — Thu, 06 Mar 2008 11:44:53 +0000

Because of rounding issues, even if I take the exact same source modules, moving from a 32-bit machine to a 64-bit machine will cause the compiled code to produce different outputs.

By: Jaye Bass

Jaye Bass — Thu, 06 Mar 2008 06:54:50 +0000

they are always done in such a fashion that others can replicate my code and results without having need to my source code.

One cannot replicate code without have the code. Your algorithm may say solve this pde, but the code for actually doing so varies greatly from modeler to modeler. You could be running on a 32 bit machine while somebody else is running on a 64 bit machine, pod sizes will be different, round off will be different, etc, and so forth. Even with an arsenal of standardized test suites its very difficult to say two different code bases are equivalent even if they are following the same requirements and top level designs.

By: Steve Moore

Steve Moore — Thu, 06 Mar 2008 02:49:18 +0000

RE: #8

…when it’s the climate scientists who are working HARDEST to find what those problems are so they can be compensated in the most effective way possible

“Compensated”?
The problems, or the climate scientists?

By: steven mosher

steven mosher — Thu, 06 Mar 2008 00:35:38 +0000

RE 29. I’ve asked questions about Crater lake at RC over the past six months.

It’s removal is a mystery.

By: Bob KC

Bob KC — Thu, 06 Mar 2008 00:23:44 +0000

Steven Mo., Re. Crater Lake, see Ellis' comment here.

By: jEez

jEez — Wed, 05 Mar 2008 23:42:16 +0000

And I apologize, my earlier comment 12 is posted in the wrong thread. Anthony, can you move the post about no data stations to the No Data For Some NASA Stations thread.

By: jEez

jEez — Wed, 05 Mar 2008 23:31:09 +0000

At a certain point, Steve’s work for NASA may prove to be invoiceable. May I suggest a name for your consulting firm–Jesterworks.

By: James A. Donald

James A. Donald — Wed, 05 Mar 2008 19:49:16 +0000

If recent measurements of the urban heat island effect are the correct order of magnitude (and why did no one except amateurs ever try to directly measure the urban heat island effect) then this whole issue is moot, because the urban heat island effect is so much larger than global warming that any attempt to measure global warming through weather stations going to have huge errors. If the results are not absurdly different from satellite and sea surface, and sea ice area measurements, this probably indicates that the compilers kept jiggering their methods till they got the result that they expected.

To get an indication of global warming through weather stations, have to select those sites that are truly rural, and always have been, and are a reasonable distance from the operators house, and always have been.

The satellite data not only gives global temperatures, but local. It would be interesting, and doubtless publishable, to compare known good weather stations with satellite measurements over time.