'It was warmer during the Holocene Climatic Optimum'

How to Talk to a Climate Skeptic

Posted by Coby Beck (Guest Contributor) at 9:10 PM on 14 Dec 2006

(Part of the How to Talk to a Global Warming Skeptic guide)

Objection: It was warmer during the Holocene Climatic Optimum than it is today -- without any human influence.

Answer: Though some temperatures during that period were in the same range as today, they were confined to the northern hemisphere and the summer months.

What's more, the cause is understood (orbital forcing similar to what controlled the Ice Ages), just as today's cause is understood (CO2 emissions), and these causes are very different. NOAA has a page on this that contains the following quote:

In summary, the mid-Holocene, roughly 6,000 years ago, was generally warmer than today, but only in summer and only in the northern hemisphere. More over, we clearly know the cause of this natural warming, and know without doubt that this proven "astronomical" climate forcing mechanism cannot be responsible for the warming over the last 100 years.

As an aside, it's worth noting that even if the Holocene had been as warm as or warmer than today, it would do nothing to undermine the theories and data that indicate today's warming is rapid and anthropogenic.

For story: 'It was warmer during the Holocene Climatic Optimum'
4 Comments | Post a Comment

Holocene? Gimme Pleistocene!

"If we drill back in time, we can get a record of how [the Ross Ice Shelf] behaved, during times, certainly in the last million years, when we know the temperatures from the ice cores suggest that the planet was two to three degrees warmer," the Andrill project member explained.

Andrill article

by jabailo at 2:42 PM on 05 Mar 2007

Uhm

If you go back any earlier than the last iceage isn't that kinda silly?

-David Ahlport

by GreyFlcn at 10:19 PM on 07 Apr 2007
[ Parent ]

Why did you quote from that article?

Mr. Bailo, did you even read the article you just quoted there?

Of course the Earth has been warmer in the past--as the article you cited states,

Previous drilling has showed that ice sheets were quite dynamic, collapsing and reforming in line with the Earth's Milankovitch cycles. These are small "wobbles" in the Earth's orbit that are known to happen roughly every 20,000, 40,000 and 100,000 years.

It goes on to comment,

But said Dr Naish, "during all those natural cycles, carbon dioxide never got above 300 parts per million. So in the last 200 years, we've had this geologically unprecedented increase in CO2 - it's 30% higher than it has been over the last several million years and it's occurred at a rate we've never seen geologically."
...
Dr Naish muses: "If they collapsed in the past without the present level of CO2 and the Earth was two to three degrees warmer, what's going to happen with the doubling of CO2 and potentially much higher temperatures?"

by Meowse at 10:59 PM on 03 Jun 2007

CO2 levels "never seen..." is incorrect

Meowse,

It may be that the context of the remark by Dr. Naish would qualify the meaning implied by his statement that you've quoted, but to simply imply categorically that contemporary atmospheric CO2 levels are at a level that have never "occurred at a rate we've seen geologically" (emphasis is mine) is incorrect; for, in fact, atmospheric C02 levels have been much, much higher (above 2000ppm). Of course, it's probably not very reassuring that those levels were associated with a mass extinction. It would be more correct to say that current C02 levels were not exceeded during the Pleistocene, which seems to be what Dr. Naish meant.

It is also important to emphasize, I believe, that asserting that climate has varied greatly without anthropogenic forcing should in no way be taken to obfuscate the likely significant consequence of such change now.

by perchecreek at 4:40 PM on 19 Apr 2008

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