Dr. Christy Rebuts Alarmist Spin on Satellite Data

By Marlo Lewis, Jr. of CEI.

"The divergence between satellite data and climate model warming predictions has long been too large for “consensus” scientists to ignore, and it keeps growing despite 2015 being anointed the “warmest year on record.”

Unsurprisingly, the usual suspects try to discredit the satellite data, even to the point of suggesting that surface records, notwithstanding their well-known heterogeneity, gaps, and quality-control issues, are more reliable.

In testimony earlier this week before the House Science Committee, University of Alabama in Huntsville (UAH) atmospheric scientist John Christy rebuts a Yale Climate Connections video featuring several heavyweights of the climate science establishment.

The video claims satellites do not actually measure temperature, but infer it from microwaves emitted by oxygen molecules in the atmosphere. That is true but irrelevant. Christy explains: “In reality, the sensors on satellites measure temperature by emitted radiation—the same method that a physician uses to measure your body temperature to high precision using an ear probe. Atmospheric oxygen emits microwaves, the intensity of which is directly proportional to the temperature of the oxygen, and thus the atmosphere. . . . As an aside, most surface temperature measurements are indirect, using electronic resistance.”

The video also claims satellites’ loss of altitude over time due to atmospheric friction—a phenomenon called orbital decay—induces a cooling bias. Again, true but irrelevant. “This vertical fall has an immeasurable impact on the layer (Mid-Troposphere or MT) used here and so is a meaningless claim. In much earlier versions of another layer product (LT or Lower Troposphere), this was a problem, but was easily corrected almost 20 years ago. Thus, bringing up issues that affected a different variable that, in any case, was fixed many years ago is a clear misdirection that, in my view, demonstrates the weakness of their position.”

Finally, the scientists in the video cite the cooling bias from the satellites’ tendency to drift from east to west. Far from being unacknowledged by Christy, the UAH team was the first to detect that bias, and corrected for it 10 years ago. Moreover, the error was not a factor in the MT layer, where observations reveal a sharp divergence from climate model projections.

For further discussion, see my blog post, “Satellites and Global Warming: Dr. Christy Sets the Record Straight.”"