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My oh Miocene!

Guest commentary by Sarah Feakins

Our recent study in Nature Geoscience reconstructed conditions at the Antarctic coast during a warm period of Earth’s history. Today the Ross Sea has an ice shelf and the continent is ice covered; but we found the Antarctic coast was covered with tundra vegetation for some periods between 20 million and 15.5 million years ago. These findings are based on the isotopic composition of plant leaf waxes in marine sediments.

That temperatures were warm at that time was not a huge surprise; surprising, was how much warmer things were – up to 11ºC (20ºF) warmer at the Antarctic coast! We expected to see polar amplification, i.e. greater changes towards the poles as the planet warms. This study found those coastal temperatures to be as warm as 7ºC or 45ºF during the summer months. This is a surprise because conventional wisdom has tended to think of Antarctica being getting progressively colder since ice sheets first appeared on Antarctica 34 million years ago (but see Ruddiman (2010) for a good discussion of some of the puzzles).
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  1. S.J. Feakins, S. Warny, and J. Lee, "Hydrologic cycling over Antarctica during the middle Miocene warming", Nature Geosci, vol. 5, pp. 557-560, 2012.
  2. W.F. Ruddiman, "A Paleoclimatic Enigma?", Science, vol. 328, pp. 838-839, 2010.

Tree Rings and Climate: Some Recent Developments

Filed under: — mike @ 8 July 2012

by Michael E. Mann, Gavin Schmidt, and Eric Steig

Update 7/12/12: Media Matters comments on the latest misrepresentations of the Esper et al study discussed in our article: ‘Surprise: Fox News Fails Paleoclimatology’
Update 7/13/12: Further comment from Bob Ward of the Grantham Institute in Huffington Post UK “The World’s Most Visited Newspaper Website Continues to Regurgitate Nonsense from Climate Change ‘Sceptics'”
Update 7/14/12: Some additional context provided by this LiveScience article

It’s been a tough few months for tree-rings, perhaps unfairly. Back in April, we commented on a study [that one of us (Mike) was involved in] that focused on the possibility that there is a threshold on the cooling recorded by tree-ring composites that could limit their ability to capture the short-term cooling signal associated with larger volcanic eruptions. Mostly lost in the discussion, however, was the fact–emphasized in the paper—that the trees appeared to be doing a remarkably good job in capturing the long-term temperature signal—the aspect of greatest relevance in discussions of climate change.

This week there have been two additional studies published raising questions about the interpretation of tree-ring based climate reconstructions.
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Far out in North Carolina

Filed under: — stefan @ 24 June 2012

The extensive salt marshes on the Outer Banks of Carolina offer ideal conditions for unravelling the mysteries of sea level change during past centuries. Here is a short report from our field work there – plus some comments on strange North Carolina politics as well as two related new papers published today in Nature Climate Change.

The Outer Banks of Carolina are particularly vulnerable to coastal erosion and sea-level rise, partly because the land is subsiding and the banks are naturally moving landward. On the ocean front, land is continually being lost.
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Fresh hockey sticks from the Southern Hemisphere

In the Northern Hemisphere, the late 20th / early 21st century has been the hottest time period in the last 400 years at very high confidence, and likely in the last 1000 – 2000 years (or more). It has been unclear whether this is also true in the Southern Hemisphere. Three studies out this week shed considerable new light on this question. This post provides just brief summaries; we’ll have more to say about these studies in the coming weeks. More »

Yamalian yawns

Filed under: — gavin @ 11 May 2012

Steve McIntyre is free to do any analysis he wants on any data he can find. But when he ladles his work with unjustified and false accusations of misconduct and deception, he demeans both himself and his contributions. The idea that scientists should be bullied into doing analyses McIntyre wants and delivering the results to him prior to publication out of fear of very public attacks on their integrity is ludicrous.

By rights we should be outraged and appalled that (yet again) unfounded claims of scientific misconduct and dishonesty are buzzing around the blogosphere, once again initiated by Steve McIntyre, and unfailingly and uncritically promoted by the usual supporters. However this has become such a common occurrence that we are no longer shocked nor surprised that misinformation based on nothing but prior assumptions gains an easy toehold on the contrarian blogs (especially at times when they are keen to ‘move on’ from more discomforting events).

So instead of outrage, we’ll settle for simply making a few observations that undermine the narrative that McIntyre and company are trying to put out.
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