The Impacts of Climate Change on Societies: What Can We Learn from the Past?

<p>This keynote presentation introduces the sources, methods, and major findings of the History of Climate and Society (HCS), a recently-coined field that uncovers the past influences of climate change on human history. It begins by offering a brief history of the field, from the eighteenth century through the present. It then describes how HCS scholars “reconstruct” past climate changes by combining what they call the “archives of nature” – paleoclimatic proxy sources such as tree rings, ice cores, or marine sediments – with the texts, stories, and ruins that constitute the “archives of society.” Next, it explains how HCS scholars in different disciplines have used distinct statistical and qualitative methods, and distinct causal frameworks, to identify the influence of climate change in the archives of society. It explores how HCS scholars conceptualize the vulnerability and resilience of past societies by introducing some telling case studies, and explaining how those case studies have grown more complex as HCS matured as a field. It then emphasizes the enduring challenges faced by HCS scholars and how, in recent months, they have been identified and are beginning to be addressed. Finally, it describes how HCS has informed climate change policy and public discourse, before offering some key lessons that policymakers can learn from the field.</p>

Precession-paced climate oscillations in Messinian sulphate evaporites recorded by carbon stable isotopes of leaf wax derived n-alkanes

<p>During the Messinian salinity crisis (MSC), the Mediterranean Sea was gradually isolated from the Atlantic Ocean due to tectonics, ultimately resulting in the deposition of enormous volumes of evaporites on the Mediterranean seafloor. In marginal Mediterranean sub-basins, the first phase of the MSC is represented by a cyclic succession of gypsum and shales (Primary Lower Gypsum unit; PLG), changing laterally into an alternation of shales, marls and carbonates towards the deeper parts of the basins. The current consensus is that the lithological cyclicity is the expression of precession-paced climate oscillations, with shales deposited during insolation maxima (precession minima) and gypsum deposited during insolation minima (precession maxima). However, this hypothesis has yet to be validated, because this assumption is primarily based on the continuation of sedimentary cyclicity from the open marine pre-MSC sediments into the Primary Lower Gypsum unit. To assess the possible role of orbitally-driven paleoclimate change on the deposition of the PLG unit, we have analysed molecular fossils (lipid biomarkers) preserved in shales and gypsum of the Pollenzo section (Piedmont basin, NW Italy).</p><p>Long-chain n-alkanes are reliable biomarkers that are used to track the input of terrestrial organic matter and allow to reconstruct paleovegetation. By using the distribution of higher plant-derived long chain n-alkanes and their compound specific carbon isotope signature (δ<sup>13</sup>C), we show that the sedimentary cyclicity in the PLG unit is indeed controlled by precession. Our high-resolution paleoclimatic proxy records cover approximately 300 Ka (6.003 Ma – 5.721 Ma) and comprise the onset of the MSC (5.971 Ma) and the first 12 cycles of the PLG unit. Cyclic fluctuation of δ<sup>13</sup>C values is observed, with higher δ<sup>13</sup>C values typifying long-chain n-alkanes extracted for gypsum, while lower values correspond to shales.</p><p>Our results, which represent the first paleoclimatic proxy data derived from Messinian gypsum, show that riverine flux of organic matter to the basin varied significantly during the first phase of the MSC. In agreement with a precessional control on paleoclimate, lower n-alkane abundance in gypsum reflects drier conditions, while higher n-alkane abundance in shales indicates more humid climate and increased input of terrestrial organic matter to the basin.</p>

PETROFYZIKÁLNÍ CHARAKTERISTIKA SPRAŠE A FOSILNÍ PŮDY V HLINÍKU U LITOVLE

Loess-paleosol sequences are an important source of terrestrial paleoclimatic proxy-data. Quaternary loess and loess loam cover the most of surface of the Upper Moravian Basin. Samples from loess-paleosol sequence in vicinity of Litovel town were studied using magnetic susceptibility, spectrophotometry and laser granulometry. Obtained petrophysical data were compared with detailed lithological description of section and geochemical characteristics determined by ED-XRF method. The results contribute to interpretation of paleoclimate in the Upper Moravian Basin during the last glacial.Section with total thickness of about 5 m is formed by loess in its upper part. This layer covers several soil horizons. It is most probably youngest loess deposit formed during the last glacial maximum. Petrophysical and geochemical data and comparison with nearby sites indicate relatively humid cold tundra conditions with bush-steppe vegetation during deposition of loess. Lithological features, position below youngest loess deposit and petrophysical and geochemical data allow interpretation of soil horizons as PK I. Low values of magnetic susceptibility indicate formation of soil in arctic interstadial conditions with higher humidity compared to interstadial average. Values of magnetic susceptibility of PK I are equal or even lower than in overlaying loess which doesn´t correspond with usual behaviour of magnetic susceptibility in loess-paleosol sequences in the Czech Republic. It could be explained by formation of soil horizons in cold interstadial climate (low production of oxi/hydroxide of Fe) supplemented by increased humidity and hence, intensive illimerization process (clay migration and Fe-minerals depletion).

FURTHER EVIDENCE FOR A “LATE ASSYRIAN DRY PHASE” IN THE NEAR EAST DURING THE MID-TO-LATE SEVENTH CENTURY B.C.?

In a recent paper published in the journal Climatic Change, we put forward the hypothesis that drought and overpopulation played an important, if indirect, role in shaping the sudden decline of the Assyrian Empire during the mid-to-late seventh century b.c. This argument was partly predicated on five paleoclimatic proxy records for conditions in different parts of the northern Near East during the first millennium b.c., each of which indicates that relatively arid conditions affected much of the region during the seventh century b.c., especially during its middle decades. Here, we revisit the textual and paleoclimatic proxy evidence for a period of drought in more depth to examine whether this evidence does in fact support the climatic component of our hypothesis. In this paper, we show that the available proxy evidence supports the notion that there was some kind of regional climatic perturbation that affected much of the Near East during the latter half of the seventh century b.c., which caused conditions in many parts of the region to become more arid. The strongest signal for this short-term episode of aridification, which we have termed the “Late Assyrian Dry Phase,” is observed at approximately 650–600 b.c. These proxies thus corroborate and provide the background for the Neo-Assyrian textual evidence for drought during the mid-seventh century b.c.