It was  reported last week by the Journal Science that, based on paleoclimate knowledge of the Middle Eocene era, sea level rise and warming were caused by very high CO2 levels.  The heightened CO2 levels were from a source not yet determined, but perhaps the destruction of carbonized rocks in Asia or intense volcanic activity. Whatever the source, it’s not happening now, but people’s  modern day activities are having a similar effect on the climate via CO2 emissions.  This valuable information is why many climate change scientists like James Hansen rely more on paleoclimate evidence than on “climate models”.

The new Know Nothings promise to ramp up their climate change denialism and anti-science political action, since the Republicans took over the U.S. Congress.  (I’m seeing more of the Know Nothings’ denialism online now than even two years ago).   For a dose of reality, here is what the Journal Science included in the November 5th issue (it’s the part the public can read without a subscription) about this:

Increased Atmospheric CO2 During the Middle Eocene

Even without humans, there are many processes that can change the concentration of carbon dioxide (CO2) in Earth’s atmosphere and affect global climate. On page 819 of this issue, Bijl et al. (1) provide the first direct evidence that very high CO2 levels occurred about 40 million years ago during the Middle Eocene Climatic Optimum (MECO), one of the hottest intervals in Earth’s climate history. The hunt is now on for a geological cause for this event—and fingers are pointing at the Himalayan mountain belt.

School of Earth and Ocean Sciences, Cardiff University, Cardiff CF10 3YE, UK.

Middle Eocene era, with the white outlines present day land masses. If we move back to a climate like that of the Middle Eocene, we will lose a lot of land mass to water.

Below is an article on Paleoclimate evidence explaining the above in more detail. It clearly shows that CO2 is the most probable culprit to explain global warming spikes in the past and present. From Solveclimate:

“… 40 million years ago, the world experienced an extreme spike in global warming. The heat was so intense that deep sea temperatures rose by about 4 degrees Celsius. This enigmatic sultry period, known as the Middle Eocene Climatic Optimum (MECO), marked a 400,000-year-long heat wave in the midst of a long era of global cooling.

Now research published Nov. 5 in the journal Science suggests the rise in surface sea temperature occurred during a time when atmospheric carbon dioxide (CO2) levels were particularly high, according to a research team from Utrecht University and the Royal Netherlands Institute for Sea Research.

First reported by U.S. scientists in 2003, the MECO warming period has been documented by data from a smattering of sites around the world. “Our paper is among the first to show that CO2 concentrations and the temperature varied hand in hand in that time,” says Peter Bijl, a paleoclimatologist [...]