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Monday, July 5, 2010

Significantly warmer Arctic surface temperatures during the Pliocene indicated by multiple independent proxies by A. P. Ballantyne et al., Geology, 38 (July 2010)

Geology, 38(7) 603-606 (July 2010); doi: 10.1130/G30815.1

Significantly warmer Arctic surface temperatures during the Pliocene indicated by multiple independent proxies

A. P. Ballantyne* (Department of Geological Sciences, University of Colorado, Boulder, CO 80309, U.S.A.), D. R. Greenwood (Department of Biology, Brandon University, Brandon, Manitoba R7A 6A9, Canada), J. S. Sinninghe Damsté (Department of Marine Organic Biogeochemistry, Royal Netherlands Institute for Sea Research (NIOZ), Texel 1797 SZ, The Netherlands), A. Z. Csank (Department of Geosciences and Laboratory of Tree-Ring Research, University of Arizona, Tucson, AZ 85721, U.S.A.), J. J. Eberle (Department of Geological Sciences, University of Colorado, Boulder, CO 80309, U.S.A.), and N. Rybczynski (Canadian Museum of Nature, Ottawa, Ontario K1P 6P4, Canada)


Temperatures in the Arctic have increased by an astounding 1 °C in response to anthropogenic forcing over the past 20 years and are expected to rise further in the coming decades. The Pliocene (2.6–5.3 Ma) is of particular interest as an analog for future warming because global temperatures were signifi cantly warmer than today for a sustained period of time, with continental confi gurations similar to present. Here, we estimate mean annual temperature (MAT) based upon three independent proxies from an early Pliocene peat deposit in the Canadian High Arctic. Our proxies, including oxygen isotopes and annual ring widths (MAT = –0.5 ± 1.9 °C), coexistence of paleovegetation (MAT = –0.4 ± 4.1 °C), and bacterial tetraether composition in paleosols (MAT = –0.6 ± 5.0 °C), yield estimates that are statistically indistinguishable. The consensus among these proxies suggests that Arctic temperatures were ~19 °C warmer during the Pliocene than at present, while atmospheric CO2 concentrations were ~390 ppmv. These elevated Arctic Pliocene temperatures result in a greatly reduced and asymmetrical latitudinal temperature gradient that is probably the result of increased poleward heat transport and decreased albedo. These results indicate that Arctic temperatures may be exceedingly sensitive to anthropogenic CO2 emissions.

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Anonymous said...

We are already at 390 ppm

Have you ever watched one of those action flicks where there's a slo-mo explosion, and Our Hero is running full out, the flames blooming out behind him? Yeah, like that. Except that there's no way that we'll be able to out-run this blast. Offset climate change? Nope. Too late. The change has already happened and now it's just the shock wave blooming out, earth's systems catching up.

A lot of people still think that it's the heat that'll do us in. It's not. It's the rapid change. How rapid? The odds are that we'll see an increase of four to six degrees Celsius by 2100. What this study says is that a lot of that extra heat will be migrating to the poles. The feeling that I get is that the equator will heat up some, but that the poles will be exponentially warmer. So, in a way, this is good news. Those 4-7 degrees will be spread out.

Change, change, change; it's all about holding it together.

Tenney Naumer said...

I think the oceans will die long before the temperatures get that high -- the destruction of the ocean floor fauna by trawling is much, much greater than most people are aware.

ccpo said...

Yup. Add to that, most people seem to be thinking in terms of the "by" dates rather than the process. Ironically, we are fond of saying it's the journey that counts, not the destination.

By failing to pay attention to the fact that we *don't* get a free ride *to* the "by" date, then we suddenly have all these troubles, but that we actually are making our way through ever more dangerous mine fields till we get to the point where anywhere we step is fraught with danger, they fail to see the true chaotic nature of what awaits.

That is, they don't get that all these forces interacting in all these strange and (unpleasantly) wonderful ways is going to have overall impacts that have us in deep doo-doo long before the "by" dates.

Not to mention the "by" dates are all fatally optimistic.


Tenney Naumer said...

ok ccpo, make my day by reminding me of this -- it is all too true