> It's a notorious inconvenience for the Greenhousers that data also
> show CO2 concentrations from the Eocene period, 20 million years
> before Henry Ford trundled out his first Model T, 300 to 400
> percent higher than current concentrations.
Wikipedia <http://en.wikipedia.org/wiki/Eocene#Climate>:
> Marking the start of the Eocene, the planet heated up in one of the
> most rapid (in geologic terms) and extreme global warming events
> recorded in geologic history, called the Paleocene-Eocene Thermal
> Maximum or Initial Eocene Thermal Maximum (PETM or IETM). This was
> an episode of rapid and intense warming (up to 7°C at high
> latitudes) that lasted less than 100,000 years [1]. The Thermal
> Maximum provoked a sharp extinction event that distinguishes Eocene
> fauna from the ecosystems of the Paleocene.
>
> The Eocene global climate was perhaps the most homogeneous of the
> Cenozoic; the temperature gradient from equator to pole was only
> half that of today's, and deep ocean currents were exceptionally
> warm.[2] The polar regions were much warmer than today, perhaps as
> mild as the modern-day Pacific Northwest; temperate forests
> extended right to the poles, while rainy tropical climates extended
> as far north as 45 degrees latitude. The difference was greatest in
> the temperate latitudes; the climate in the tropics however, was
> probably similar to today's.(Stanley, 508)