A Hot Time in the Old Eocene

One of life's truths is that people are people, regardless of their age, sex, nationality, and so on—even if they're scientists. And like kids to Pokemon, scientists all tend to gravitate toward the craze of the day, forgetting that today's Pokemon are yesterday's Teletubbies.

In climatology, today's Pokemon is the notion that carbon dioxide is the main driver of Earth's temperature. When it was unfrigid—before the last ice age—CO₂ concentrations were high, and when the glacier ate Chicago, CO₂ was low.

There's nothing so unnerving as to watch supposedly intelligent people, like scientists, all buying the same idea (almost as unnerving as watching your supposedly intelligent son and his Poke-pals). Many are the university seminars where some esteemed figure stands and tries to explain that almost all climate changes are ultimately caused by dreaded carbon dioxide.

Reality is beginning to intervene. The first crack was when so-called "skeptics" noticed that temperature changes during recent glacial cycles occurred, in many instances, before the carbon dioxide changed. This was largely determined by visual inspection of ice-core records that the herd, with the Vice President leading the charge, routinely cited as the best evidence that CO₂ controlled climate.

Then came Hubertus Fisher's study, which showed the skeptics had correctly divined the ice cores. Now comes a study by Paul Pearson and Martin Palmer showing that the CO₂ concentration in the Eocene (43 million years ago), when temperatures reached their post-dinosaur peak, was perhaps only two-thirds the value seen at the end of the last ice age! This followed fast the publication by Pagani and colleagues showing the concentration was around 240 ppm (vs. 270 ppm at the end of the ice age) 17 million years ago, when the ocean was about 6°C warmer than it is today.

Sharon Cowling, writing in the latest issue of Science, summarized these findings dispassionately: "Recent estimates of CO₂ concentrations of 180 to 240 [ppm]...between 17 and 43 million years ago are well below modern CO₂ concentration of 360 ppm."

About all of this, Texas A&M Climatologist Tom Crowley said, "It could be the whole carbon dioxide paradigm is crumbling." But he added that CO₂ will still likely warm the world in the next century. Dear Mom....I was wrong...please send money.

The real question now is, what will become the next climatological Teletubby?

References:

Cowling, S., 1999, Plants and Temperature—CO₂ Uncoupling, Science, 285, 1500–1501.

Fisher, H., et al., Ice core records of atmospheric CO₂ around the last three glacial terminations. Science, 283, 1712–1714.

Pagani, M., et al., 1999, Miocene evolution of atmospheric carbon dioxide. Paleoceanography, 14, 273.

Satellites Rule!

The satellite-based MSU temperature record—which has shown substantially less warming than surface temperatures or model predictions—is subject to frequent assault by party-line global warmers.

But these attacks are easily deflected because, on an annual basis, the satellite temperatures match up extremely well with temperatures derived from radiosondes (weather balloons) based on Jim Angell's 63-station global network. Still, this radiosonde network has been criticized for inconsistencies over time from a variety of causes, including changes in instrumentation.

To determine whether these inconsistencies constitute a real problem, Angell recently looked at temperatures derived from a much more homogeneous and dense 120-station radiosonde network for the United States and Canada.

Angell calculated temperature changes over 10 degree–wide latitude bands from radiosonde surface temperatures; average temperatures in the 850-300 mb layer (the troposphere—lower atmosphere), the 300–100 mb layer (the tropopause—middle atmosphere); and the 100–50 mb layer (the lower stratosphere—upper atmosphere). He then compared these slopes with 1) temperature calculated from the North American stations pulled from his original 63-station global radiosonde network and 2) MSU satellite temperatures.

The results show very good agreement among all three sets of measurements. The dense North American network trends match up well with the readings from the global network over the same region, with the exception of the subtropical tropopause, where there is a commonly recognized bias. Furthermore, the satellite readings fall well within the expected range.

Angell's finding provides fairly convincing evidence that the radiosonde temperature records are reliable and further boosts the quality and reliability of the MSU satellite records.

Anyone wishing to find fault with them will have to try harder.

References:

Angell, J.K., 1999, Variation with height and latitude of radiosonde temperature trends in North America, 1975–1994, Journal of Climate, 12, 2551–2561.