Evidence Of MWP In Argentina
By Paul Homewood
Rog has news of the latest study, suggesting that the MWP was real, this time in Argentina:
Vilanova et al. (2015) developed a multi-proxy millennial environmental record from sediment cores extracted from Laguna Nassau, a shallow lake that apparently developed within a blowout depression in the semi-arid sandy lowlands of the Western Pampas of Argentina.
And as they go on to report, “this multi-proxy stacked record reveals the evolution of an incipient water body subjected to warm and dry conditions from ~900 to 770 cal yr BP, an interval that is coeval with the Medieval Climatic Anomaly,” which is also more commonly known as the Medieval Warm Period or MWP.
Continuing, the five researchers write that the buried remains of the highest percentages of Celtis — commonly known as hackberries or nettle trees, which represent a genus of about 60-70 species of deciduous trees widespread in warm temperate regions — in the Laguna Nassau pollen record suggest the existence of “a semi-arid climate and indicate that [drum roll] drier and warmer conditions than today predominated in the area from about 900 to at least 770 cal yr BP.”
And so we have yet another well-documented example of the pure and simple fact that the much-studied Medieval Warm Period likely was somewhat warmer than the Current Warm Period has been to date, and during a time when the atmosphere’s CO2 concentration was only about 280 ppm, compared to the approximate 400 ppm of today.
And these facts further suggest that the historical increase in the air’s CO2 content that began with the Industrial Revolution may have had nothing at all to do with the development of the Current Warm Period, which still has a substantial way to go before it reaches the degree of warmth that characterized the peak warmth of the MWP.
This adds to many other studies which show evidence of the MWP and LIA in South America.
For instance, this paper by Polissar et al, concerning Venezuela:
Back in 1986, Lonnie Thompson was honest enough to admit the same in Peru:
The analyses of two ice cores from a southern tropical ice cap provide a record of climatic conditions over 1000 years for a region where other proxy records are nearly absent. Annual variations in visible dust layers, oxygen isotopes, microparticle concentrations, conductivity, and identification of the historical (A.D. 1600) Huaynaputina ash permit accurate dating and time-scale verification. The fact that the Little Ice Age (about A.D. 1500 to 1900) stands out as a significant climatic event in the oxygen isotope and electrical conductivity records confirms the worldwide character of this event.
It was also Thompson who wrote in 2003 that:
For the Quelccaya Ice Cap (13.93°S, 70.83°W), this work revealed that peak temperatures of the MWP were warmer than those of the last few decades of the 20th century.
Areneda et al found similar in Chile:
These data allow us to infer that the last maximum advance of Cipreses glacier, in Chile, attributable to the ‘Little Ice Age’ occurred around AD 1842. The first historical retreat was recorded in 1858 and, since then, the glacier has shown a clear retreating trend with no new advances. All this information was compared with the historical data gathered for San Rafael glacier, which shows the occurrence of a cold period contemporary with the European LIA.
Also from Areneda:
Past ice lobe behaviour at Laguna San Rafael is described in documents provided by Spanish and then Chilean explorers from the late seventeenth to the early twentieth centuries. These records begin in AD 1675, when temperate conditions, probably similar to those at present, prevailed. At that point, the glacier was confined within its valley, not penetrating the Laguna. The glacier advanced noticeably during the nineteenth century and probably reached a maximum position for the `Little Ice Age’ around AD 1875. The historical sources suggest a slight retreat in AD 1904 in relation to the conditions prevailing 29 years earlier. The historical data show that the eighteenth to nineteenth century cooling period at San Rafael glacier was within the temporal window of the European `Little Ice Age’. This work provides independent, direct historical evidence for the occurrence of this event in southern Chile.
And in Patagonia, the retreat of the Jorge Montt Glacier is uncovering the remains of 400 year old forests.
These studies don’t necessarily prove that temperatures were as warm in the Middle Ages as now in South America. But what they do show in conclusive fashion is that the there was a marked cooling there during the Little Ice Age, and that there was, by definition, a much warmer period before.