May 9, 2008

Lessons of the Quaternary

Filed under: Climate History

When climatologists talk about the Quaternary Period, you probably think they are referring to events that occurred thousand of years ago. You would likely be right, but for the official record, the Quaternary Period is the geologic and climatic time period that began roughly 1.8 million years ago and includes the present. The Quaternary includes two major geologic epochs including the relatively cold Pleistocene when glaciers ruled the Earth and the Holocene period that began approximately 12,000 years ago when the glaciers retreated. We see the climate alarmists sometimes arguing that we have left the Holocene and entered the Anthropocene – a time when the human impact has significantly altered the Earth. So, we are currently living in the Quaternary, Holocene, and Anthropocene, all at the same time.

One of the world’s leading journals focusing on the geology, geomorphology, geography, archaeology, soil science, palaeobotany, palaeontology, and palaeoclimatology of the Quaternary Period is published by Elsevier and is titled Quaternary Science Reviews. Three articles have been published recently in the journal with what we are calling the “Lessons of the Quaternary.”

The first article of interest was generated by a team of scientists from Norway, Canada, and Russia and deals with glaciers in the northern Ural Mountains of Russia. Their shocking and revealing title is “Glaciers in the Polar Urals, Russia, were not much larger during the Last Global Glacial Maximum than today.” Are they kidding — is this some kind of spoof? Every presentation on global warming insists that glaciers are retreating the world over, but these clowns are trying to tell us that the glaciers of the Urals are no smaller today than during the time when glaciers all over the world were at their maximum? Well, Mangerud et al. went to the northern Urals during the summer of 2000 and collected quartz samples from boulders left behind from glacial advances. It is a long story, but ratios of various beryllium isotopes can be used to date when the boulders were deposited. Consistent with many other studies, they found that the Last Glacial Maximum was indeed around 21,500 years ago. This may not go over well with the climate alarmists, but Mangerud et al. conclude “that the restricted growth of the Chernov
Glacier during the Last Global Glacial Maximum (LGM) is representative for most of the other glaciers in the Polar Urals, i.e. they were not much larger than at present.”

Next up is a piece produced by 13 scientists who focused on climate change in Central America over the past 85,000 years. The Hodell et al. team came from leading institutions in Florida, Switzerland, California, and Germany and they headed to Guatemala to extract cores from the bottom of Lake Petén. The layers in the core would alternate from clay to gypsum reflecting wet and dry conditions. Furthermore, they analyzed the chemical and physical properties of the layers and related them to climate (and sea surface) conditions. A portion of one of their figures (see Figure 1) really caught our eye. The plot is reconstructed sea surface temperatures from the Atlantic Ocean off the coast of Guatemala for the past 32,000 years. If global warming is your thing, you really missed it – notice the 12°C warm-up from 15,000 years ago to 10,000 years ago. We see no warming at all during the Anthropocene; we also notice how much more variable the climate was during the cold periods, not the warm ones.


Figure 1. Reconstructed Atlantic sea surface temperatures (from Hodell et al., 2008)

Our final stop on the Quaternary tour takes us to west-central Minnesota where organic material has been collecting at the bottom of Lake Mina. A team of scientists from Queen’s University in Canada cored the lake and very carefully analyzed and dated the pollen spores from each layer (each layer is called a varve). St. Jacques et al. state “In total, 886 varves were counted, from AD 1116 to 2002, with average thickness 1.4 mm and standard deviation 0.7 mm.” To say the least, carefully analyzing each of the 886 layers is tedious work. In their words, the team concludes “The period of the so-called Little Ice Age (LIA) (AD 1500–1870) was colder than the Medieval Climate Anomaly (MCA) (AD 1100–1500) in west-central Minnesota. Winter temperatures in the LIA declined more than summer ones. The pollen record suggests that the LIA occurred in three phases: an initial cold phase from AD 1505 to AD 1575, a warmer phase, and then a very cold phase from AD 1625 to AD 1775. There were severe droughts detected in the Lake Mina record from AD 1660 to AD 1710 and AD 1300 to AD 1400, suggesting that high-resolution pollen records can detect events previously defined from the tree-ring records. This latter century-scale drought is concurrent with the widely reported ‘‘AD 1250–1400 mega-drought,’’ which exceeds the severity of 20th century droughts.” So while the climate alarmists warn us of upcoming severe droughts, the St. Jacques et al. team shows us that much bigger droughts have occurred in the past both in relatively cold and warm periods.

The Quaternary has a lot to tell us about how the climate system behaves in warm and cold periods, and while we at World Climate Report are listening, we suspect the global warming crusade will have little to do with the lessons of the Quaternary.

References:

Hodell, D.A., F.S. Anselmetti, D. Ariztegui, M. Brenner, J.H. Curtis, A. Gilli, D.A. Grzesik, T.J. Guilderson, A.D. Müller, M.B. Bush, A. Correa-Metrio, J.Escobar, and S. Kutterolf. 2008. An 85-ka record of climate change in lowland Central America. Quaternary Science Reviews, doi:10.1016/j.quascirev.2008.02.008

Mangerud, J., J. Gosse, A. Matiouchkov, and T. Dolvik. 2008. Glaciers in the Polar Urals, Russia, were not much larger during the Last Global Glacial Maximum than today. Quaternary Science Reviews, doi:10.1016/j.quascirev.2008.01.015.

St. Jacques, J.-M., B.F. Cumming, and J.P. Smol. 2008. A 900-year pollen-inferred temperature and effective moisture record from varved Lake Mina, west-central Minnesota, USA. Quaternary Science Reviews, 27, 781–796.




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