Arctic Past, Arctic Future

Quite a few readers found it hard to believe the findings in my front-page story Thursday, in which scientists extracted sediment from the seabed near the North Pole and found that a big natural greenhouse-gas buildup and planetary hot spell 55 million years ago created Florida-surf temperatures (74 degrees average) in the Arctic Ocean.

This letter below is typical of a batch. See my response farther down. I also spoke about some of this on the Diane Rehm Show this week and will be in NPR's Science Friday today.
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Mr. Revkin, Your article about a tropical Arctic was very interesting. I did notice some topics not mentioned. Where was the Arctic region 55 million years ago? Could it had been warmer due to plate tectonics having moved it through a warmer latitude? Also, if the warm up was indeed due to an increase of greenhouse gases, when mankind and his suv's weren't around, how can we be to blame now? I think this research supports the argument that we have little influence in todays climate. I do not deny that the Earth may be warming, I do however, not believe my lawn mower is the cause. There are still too many unknowns to conclude we are causing any kind of global warming. Knowing that the sun is hotter, plate tectonics are at work, and gas-belching volcano's are active tell me that there is much more to this climate thing than experts and the media portray. I for one am not a believer, however I do what I can to protect my environment and conserve. This planet will be here long after we are all gone.

Revkin responds:

Thanks for writing,
Others asked the same questions. The story makes clear -- and many scientific reports make clear -- that there is no natural explanation for the current greenhouse-gas buildup. There is absolutely no dispute about that. So the lesson there, scientists say, is that we are replicating a natural event that profoundly transformed the world.
    I sent the scientists a query from another reader about the orientation of the Arctic Ocean and continents 55 million years ago, and they provided a long detailed description of the evidence showing that the orientation was essentially the same as it is now.
    I'm sure they'd be happy to fill you in. Kate Moran, kate.moran@uri.edu, was a co-chief scientist on the project. Matthew Huber is another member of the team: huberm@purdue.edu.
    And of course your lawn mower alone is not the cause of current warming. But it's quite clear now to just about every scientist studying this issue -- including Dr. Richard Lindzen who has decried the alarmism of late -- that more carbon dioxide from sources like lawn mowers, cars, power plants, burning forests, and 9 billion people will indeed warm the planet.
    The only question being debated now is what to do about it -- how aggressively to act to curb the emissions.
    Please explore www.nytimes.com/learning/globalwarming for more.
    Andy Revkin