Monday, September 27, 2010

Global Temperatures: Who is Right?

I've always said that I'm never a fan of politics.  I give each side of every argument a fair shake regardless of my personal opinions of beliefs. Its my open-mindedness to other information and data that has allowed me to change my opinion on many issues based on newly acquired knowledge.  Politics--as with every hot-button issue--clouds the landscape.

In climate science, the data is the foundation of the field.  This analysis focuses on the two datasets that is often sited and dissected as to what is more valid and reliable.  One represents the ground temperatures.  The other represents the atmospheric temperatures measured from satellites.

The first set is from the Goddard Institute of Space Studies (GISS).  This dataset goes back more than 100 years of record keeping.  The second originates from the Advanced Microwave Sounding Unit (AMSU-A) flying on NASA’s Aqua satellite.  Satellites like the AMSU have been measuring the atmosphere since 1979.

The first graph is from GISS.  NASA and NOAA use this dataset in determining long term trends commonly sited.  The data is from 1880 to the present.  I noted the satellite era on the right with two solid red vertical lines.

The second graph is from the UAH website showing the satellite data since 1979.  I added the average temperature rise in red.  All data is available on the web for verification.

The question doesn't come from whether global temperatures have warmed or cooler since 1979 (warming has occurred) but to what degree.  One dataset shows between 0.7 and 0.9 degree celsius increase.  The other shows a 0.4 degree celsius increase.

Furthermore, can the increase be described best using naturally occurring cycles or does the increase in Carbon Dioxide have the most effect?

So what dataset is right?


Brad said...

Satellite Measurements are the most accurate, and really the only global measurements that can be trusted with any reasonable degree of certainty.
Consider these facts that when discussing surface temperature records since 1871:
1) We've changed the location we've taken the temperatures from several times. (Shady side of Building, Vented Box, etc.)
2) We've changed the type of instrument measuring the temperature several times
(Mercury to Alcohol, analog to digital to ASOS).
3) The places we have take the observations from have undergone significant change in their landscape. (Think Central Park in 1871 and Central Park today.)
4) Since the population of the globe covers less than 3% of the planet, you aren't getting very accurate coverage. (London? Sure. Middle of the Gobi desert? Not quite.)

Since terrestrial temperature records were the ones used to concoct the Manmade Global Warming scam, You can see why I am skeptical.

Bob said...

Your GISTEMP graph is land only to compare like to like GISTEMP land+ocean should be used, which shows slightly less warming (as the ocean has warmed slower than land, as would be expected)

There is also another satellite record and another surface record to compare.

UAH satellite record: 0.44C warming since 1979

RSS satellite record: 0.51C warming since 1979

GISTEMP surface record: 0.52C warming since 1979

HadCRUT surface record: 0.49C warming since 1979

The satellites are not measuring the surface temperature trend but the trend of the entire lower troposphere, so there is no reason to expect any particular satellite record trend to match a particular surface record trend.

But there is reason to expect the two satellite trends to match as they are measuring the same thing. So that's the biggest disagreement.