Archive for the ‘Publications’ Category
This week’s issue of Science contains a new study of ice cores from the Quelccaya ice cap in the Peruvian Andes. Thompson et al. take advantage of new measurement techniques to present an annually resolved record of past climate. The largest signal in the record is the Little Ice Age, especially during c.1520-1680AD, a period marked by particularly low oxygen isotope ratios, highly correlated to lower temperatures. Records of nitrate and ammonium ions give further clues to changes in regional circulation, including a possible southward shift in the Intertropical Convergence Zone during the Little Ice Age. However, the authors are cautious about drawing further conclusions regarding the source of these signals.
A new global multiproxy reconstruction finds that while the first decade of the 20th century was among the cold 5% since the start of the Holocene, current temperatures are among the highest in 5000 years. The study by Shaun Marcott et al., published here in Science, largely confirms the earlier reconstructions of Mann et al. for the past two millennia. For the benefit of climate historians, the authors also find a distinct Medieval Warm and Little Ice Age in their reconstructions.
The article D.M. Anderson et al., “Global Warming in an Independent Record of the Past 130 Years,” published here in Geophysical Research Letters, uses an index of 173 temperature-sensitive proxies to reconstruct global temperatures going back to 1880, and a smaller index of 67 proxies to extend the record back to 1730. The results strongly mirror those of the instrumental record, with clear indications of accelerating warming in the 20th century. The study notes that “The upward trend appears to begin in the early 19th century but the year-to-year variability is large and the 1730-1929 trend is small.”
Of course, for climate historians the study also serves as a nice confirmation of the validity of proxies in historical climate reconstruction. The broad Paleo Index used in the study actually shows much stronger correlation with the instrumental record than single, local proxies tend to do.
A new study in this week’s Science (see also the news article here, and the lengthier analysis on HistoricalClimatology.com) uses U-Th dating on a stalagmite in Belize to offer the most convincing evidence yet that the conflict and settlement abandonment of the lowlands Maya Terminal Classic Period (~800-900AD) took place against a backdrop of severe recurring drought. While past studies of lake sediments pointed to a similar conclusion, this speleothem research offers the most local, precisely dated, and high-resolution information to date. As in similar studies in other parts of the world, the oxygen isotope data recovered won’t be a perfect representation of regional precipitation; but in this case the overlap of the finds with other proxies and, in the case of the 16th-century droughts, with historical records is highly suggestive. This story has also picked up some coverage in the media as another cautionary tale for contemporary climate change.
Another study, published in the latest issue of PNAS has found a modest but statistically significant correlation between climate and conflict in Africa since 1990. In particular, the authors find that especially high rainfall correlates with reduced conflict and especially high temperatures correlate with elevated conflict. The results fit with a growing list of studies fitting past climate anomalies with war and violence (even though most of these studies only consider linear correlations rather than thresholds, consider temperature and precipitation separately rather than as drought indices, and neglect the duration and seasonality of anomalies). This one has picked up a little coverage in the press, too.
For those looking for teaching resources on climate and conflict, Yale Environment 360 has produced a short free online video here.
The study of lakes in the Svalbard Islands, published in Geology and reported on the Earth Institute website, recreates 1,800 years of data at decadal to multi-decadal resolution using the biological properties of algae buried in sediments. The results show modern warming easily in excess of records reached in the Medieval Warm Period. The study also indicates that summers during the Little Ice Age were not especially cold, suggesting that the glacial expansion of the period may have been due to higher winter precipitation.
The best climatic reconstructions are compiled at the intersection of the sciences and the humanities. Climatic data from scientific “proxy data,” like ice cores or tree rings, can be refined using weather descriptions in historical evidence written by contemporary observers. The most useful documents for the reconstruction of past climates are often the most simple and the easiest to quantify. In the straightforward weather observations provided in ship logbooks or financial accounts, for example, relationships between weather, its environmental consequences, and human observers are often the clearest. Describing a simple environmental phenomenon with an easily identifiable meteorological cause, easily quantifiable records of river freezing are especially valuable. Used for decades by Dutch scholars, they have recently been applied to a central European context by an international team of researchers under Frank Sirocko of Johannes Gutenberg University. More . . .
A recent article in the Irish Times reports Dr. Alan Smyth at Trinity College has identified Isaac Butler as the author of a unique weather diary for early 18th-century Dublin. The journal covers the period 1716 through 1734 and describes some of the particularly cold wet summers of the period. The full document has been posted free online by the Dublin City Public Library at: <http://dublincitypubliclibraries.com/story/diary-weather-and-winds>. (Thanks to CHN member Mark Humprhies for drawing this to my attention.)
A new episode of the Exploring Environmental History podcast examines aspects of historical climatology. The guest on this episode of the Podcast is Dagomar Degroot, a PhD Candidate in environmental history at York University in Toronto, Canada. His research explores the issue of how the changing climate of the Little Ice Age influenced the cultural, military and economic histories of the Dutch Republic during the early modern period. Dagomar discusses some of the pitfalls of this type of research, the sources available to historian’s researching climate and the relevance to present day debates about global warming and climate change.
To listen to the podcast, go to the Environmental History Resources website at:
Follow the podcast on Twitter: @EH_Resources
The winter 2012 edition of Zeithistorische Forschungen (Contemporary History) includes a new article by CHN member Franz Mauelshagen, “„Anthropozän“: Plädoyer für eine Klimageschichte des 19. und 20. Jahrhunderts,” also available in English translation.