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Roman Warming (was it global?)

Gullible Rudd steps right in it

Rudd let slip a line in his frustration this week that reveals how little he knows about the topic he holds so dear. He has so completely swallowed the PR on climate science, that when poked, he reflexively fires back exaggerated scientific claims that would make even the IPCC blush. In 2007 the IPCC and Gore et al offered Rudd the perfect Election-Wedge-on-a-Platter. They’d primed the audience with propaganda; trained the crowd to recite: Carbon is pollution. It looked like a no-brainer. Yet having based his leadership and campaign on it, it’s obvious he had not done even the most basic of checks (and still apparently hasn’t).

It’s an abject lesson in the importance of doing some homework before rewriting a nation’s economy.

Roman Statue's aren't dressed for cold weather

Toga's don't keep you warm

Last week Tony Abbott (the Australian opposition leader) told school children that it was warmer ”at the time of Julius Caesar and Jesus of Nazareth”. This banal line set off a flurry of denial and bluster.

Rudd was incredulous in the Parliamentary Hansard record to the opposition members last week:

…how is it that, in the 21st century, you could support this Leader of the Opposition, who says that the world was hotter in Jesus’ time? How could you actually hold to a belief, in defiance of total science around the world, that somehow in the last 2000 years the world has become cooler, not warmer? How could you stand behind a leader who says that the industrial revolution, in effect, did not happen?

In defiance of “total science”? Or totalitarian science?

It’s true it’s difficult to know the exact temperature of the globe in the year one (it’s difficult to know the exact global temperature in 1975, too), but there are scientists reporting in journals from all over the world that back up Mr Abbott. We know it really must have been warmer in Europe thanks to written historical records and artefacts that pop out of melting glaciers. As William Kinninmonth points out, Hannibal took an army of elephants across the Alps in winter in 200 BC. And we all know that the Romans are not known for wearing fur coats.

Rudd is apoplectic with the non-sequiteur about the industrial revolution: If temperatures were warmer in 10BC, somehow that nullifies the steam engine 1800 years later? In Rudd-land, no one can even imagine the parallel universe where  carbon might not control the climate.

A warmer world in Roman times?

A quick tour of peer reviewed research around the globe shows it was also warmer in China, North America, Venezuela, South Africa, and the Sargasso Sea 2000 years ago. And of course, Greenland tells an evocative tale.

Greenland temperatures – cooling for 3000 years

Greenland Temperatures - last 10,000 years

Long-term, temperatures have been declining for at least 3000 years. The graph stops about 100 years ago but even allowing for the extra rise in the last century, temperatures today are cooler than  in Medieval times and cooler than Roman times. It’s clear from hundreds of studies that the medieval warm period was a global phenomenon and was warmer than today. Some of the studies below may not include modern temperatures, but they show that the Roman era was comparable to Medieval times.

Thanks to the Craig Idso at CO2Science for compiling so many of these on his site.

Great plains of North America

Source (Nordt 2008)

Nordt, L., von Fischer, J., Tieszen, L. and Tubbs, J. 2008. Coherent changes in relative C4 plant productivity and climate during the late Quaternary in the North American Great Plains. Quaternary Science Reviews 27: 1600-1611.

Makassar Strait  (Indo Pacific)

Source: Oppo 2009

Reference: Oppo, D.W., Rosenthal, Y. and Linsley, B.K. 2009. 2,000-year-long temperature and hydrology reconstructions from the Indo-Pacific warm pool. Nature 460: 1113-1116.


East China Sea Warming Roman Times

Source: Fengming 2008.  For more: See also, and here and East China Sea.

Fengming, C., Tiegang, L., Lihua, Z. and Jun, Y. 2008. A Holocene paleotemperature record based on radiolaria from the northern Okinawa Trough (East China Sea). Quaternary International 183: 115-122.

Sargasso Sea (Atlantic Ocean)

The Atlantic was warmer too

Keigwin, L.D. 1996. The Little Ice Age and Medieval Warm Period in the Sargasso Sea. Science 274: 1504-1507.

See also  Richter 2009

Richter, T.O., Peeters, F.J.C. and van Weering, T.C.E. 2009. Late Holocene (0-2.4 ka BP) surface water temperature and salinity variability, Feni Drift, NE Atlantic Ocean. Quaternary Science Reviews 28: 1941-1955.


Venezuela temperatures in Roman Times

Source: Black 2004

Black, D. E., Thunell, R. C., Kaplan, A., Peterson, L. C. and Tappa, E. J. 2004. A 2000-year record of Caribbean and tropical North Atlantic hydrographic variability. Paleoceanography 19, PA2022, doi:10.1029/2003PA000982.

South Africa

South African Cave last 3000 years

South African Cave last 3000 years

Source: Holmgren 2001. See also here and here in African reconstructions.

Holmgren, K., Tyson, P.D., Moberg, A. and Svanered, O. 2001. A preliminary 3000-year regional temperature reconstruction for South Africa. South African Journal of Science 97: 49-51.

The Southern Ocean 7000 year record also shows long term cooling as well as the Roman Warm Period.

Vostok Antarctica, last 12,000 years

Vostok seems to move according to it’s own local agenda (probably due to it being whiter, colder and more isolated than anywhere else). But none-the-less, the long term curve — the big swing — matches the Greenland record, and temperatures peaked thousands of years ago and are on a general long term slide.

LATE POST ADDITION: I wouldn’t draw too many conclusions from the trendline of Antarctic data, the graph is there for completeness. There’s a linear downtrend over the last 5000 and last 12,000 years as well, but I doubt it’s statistically significant. What matters for this post is that if many places around the rest of the globe were warmer 2000 years ago, to counter that, Antarctica would need to be dramatically cooling to keep the average the same. For Kevin Rudd to be right– and to claim the world has warmed from 2000 years ago, Antarctica would need to be very very cold. It wasn’t.

Vostok Antarctica, last 12,000 years

Charlie B and Chris both pointed out that a study in shells off Iceland shows the Roman Warm Period (RWP) and the MWP. (Can someone test shells around Australia?)

“No Scientists” eh Mr Rudd?

Name the scientist who claims it was globally cooler in Roman Times.

Thanks to Baa Humbug for finding the Hansard quote and helping with the graphs.

H/t Mattb for asking about the trend.

UPDATE: 8-12-2011 Headline changed to reflect the more useful long term point of this post.

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