Watts Up With That? points to a new study in Nature that admits that during the late Miocene era (12 million to 5 million years ago), atmospheric carbon dioxide levels and temperature were "decoupled" (unlike today). From the press release:
Until now, studies of Earth’s climate have documented a strong correlation between global climate and atmospheric carbon dioxide; that is, during warm periods, high concentrations of CO2 persist, while colder times correspond to relatively low levels.
However, in this week’s issue of the journal Nature, paleoclimate researchers reveal that about 12-5 million years ago climate was decoupled from atmospheric carbon dioxide concentrations. New evidence of this comes from deep-sea sediment cores dated to the late Miocene period of Earth’s history.The argument is that a lot of other factors have come into play in the last five million years, including changes in ocean currents, so that now atmospheric carbon dioxide is an important determinant of global temperatures, while it wasn't in the past.
During that time, temperatures across a broad swath of the North Pacific were 9-14 degrees Fahrenheit warmer than today, while atmospheric carbon dioxide concentrations remained low–near values prior to the Industrial Revolution.
Hmmm. And how do we know that it is an important determinant today, when carbon dioxide levels keep rising, but temperatures have suddenly started dropping (although only slightly)? Because the global warming believers keep fudging their data to make it so!