Little Ice Age Was The Coldest Period For 10000 Years

By Paul Homewood

We regularly hear claims of “record breaking” and “unprecedented” temperatures in Arctic regions. However, as the records usually only go back to the 19th C, these statements are pretty meaningless.

There are in fact many scientific studies that show the Little Ice Age, which came to end in the late 19th C, was the coldest period in these regions for maybe 10000 years.

We have already seen studies by Jorgen Peder Steffensen (based on ice cores) and Ribeiro et al (dinoflagellates), which both come to the same conclusion. Let’s take a look at four more.

1) Kelly and Long – “The Dimensions of the Greenland Ice Sheet since the Last Glacial Maximum”

Based on radiocarbon ages of marine shells and reworked terrestrial organic material incorporated into historical moraines, environmental conditions registered in lacustrine sediments, and submerged coastal features, it has been suggested that the Greenland Ice Sheet receded tens of kilometers within its present day margins during the early and mid Holocene (e.g., Kelly, 1980 and references therein). This ice sheet recession was likely a response to the warmer temperatures of the Holocene Thermal Maximum (9-5 ka) (e.g., Kaufman et al., 2004), which is registered by Greenland ice cores as ~2.5°C warmer than at present (Dahl-Jensen et al., 1998).

A critical question is to determine the dimensions of the ice sheet at the end of this warm interval, prior to the Neoglacial (~4 ka-present) readvances. In many locations the ice sheet and mountain glaciers reached their maximum extents since the early Holocene during the Little Ice Age (ca. A.D. 1290-1850) (e.g., Kelly, 1980; Hall et al., 2008b; Kelly et al., 2008).

2) C J Caseldine – “The Extent of Some Glaciers in Northern Iceland during the Little Ice Age”

Lichenometric studies from four glaciers in Northern Iceland are used to determine the dates of their Little Ice Age maxima. In all cases these date to the last half of the 19th C and probably marked the maximum Neoglacial extent of the glaciers.

3) Vinther et al – “Holocene of the Greenland Ice Sheet”

The previous interpretation of evidence from stable isotopes (δ18O) in water from GIS ice cores was that Holocene climate variability on the GIS differed spatially 3 and that a consistent Holocene climate optimum—the unusually warm period from about 9,000 to 6,000 years ago found in many northern-latitude palaeoclimate records 4 —did not exist. Here we extract both the Greenland Holocene temperature history and the evolution of GIS surface elevation at four GIS locations. We achieve this by comparing δ18O from GIS ice cores 3, 5 with δ18O from ice cores from small marginal icecaps. Contrary to the earlier interpretation of δ18O evidence from ice cores 3, 6 , our new temperature history reveals a pronounced Holocene climatic optimum in Greenland coinciding with maximum thinning near the GIS margins. Our δ18O-based results are corroborated by the air content of ice cores, a proxy for surface elevation 7

4) Levac et al – “Sea Surface Conditions in Northernmost Baffin Bay during the Holocene”

The analysis of cores collected in northernmost Baffin Bay, from within the area of the North Water Polynya, permits definition of a composite sedimentary sequence ca. 12 m thick spanning the last 10 000 14C yr, with only a few discontinuities. Palynological analyses were performed in order to reconstruct changes in surface water conditions and biogenic production. Transfer functions, using dinocyst assemblages, were applied to estimate sea-surface temperature (SST) and salinity, as well as the seasonal duration of sea ice cover. At the base of the record, prior to 9300 14C yr BP, dinocysts and organic linings of benthic foraminifers are sparse, indicating harsh conditions and low productivity. After ca. 9300 14C yr BP, the increased concentration of benthic foraminifers (up to 103 linings cm−3) and dinocyst fluxes (102–103 cysts cm−2 yr−1) reveals high biological productivity related to open-water conditions. The early to middle Holocene, from ca. 9000 to ca. 3600 14C yr BP, is marked by relatively high species diversity in dinocyst assemblages and the significant occurrence of autotrophic taxa such as Spiniferites elongatus, Pentapharsodinium dalei and Impagidinium pallidum. This assemblage suggests conditions at least as warm as at present. From ca. 6400 to ca. 3600 14C yr BP, transfer functions indicate warmer conditions than at present, with SST in August fluctuating up to 5.5°C. After 3600 14C yr BP, the dinocyst record suggests a trend of decreasing temperature toward modern values, marked by recurrent cooling events.

Why does any of this matter?

We are told the current climate is “unprecedented” - it is not.

We are told Arctic warming will have dangerous consequences – it did not.

We are told of dangerous tipping points – they did not happen.

The reality is that for the last 4000 years the climate, at least in much of the Northern Hemisphere, has been steadily cooling down, albeit interspersed with warmer interludes. If the pattern continues, the next Little Ice Age, due in a couple of hundred years or so, will be colder than the last. Then we really will have something to worry about.

References

1) http://www.pages-igbp.org/products/newsletters/2009-2/Special%20section/science%20highlights/Kelly+Long_2009-2%2860-61%29.pdf

2) http://www.jstor.org/discover/10.2307/633535?uid=3738032&uid=2&uid=4&sid=56007264403

3) http://www.nature.com/nature/journal/v461/n7262/full/nature08355.html

4) http://onlinelibrary.wiley.com/doi/10.1002/jqs.614/abstract