Archives par mot-clé : History

Nature Unbound V – The elusive 1500-year Holocene cycle

by Javier,  September 15, 2017, in Judith Curry Climate Etc.


The existence of a 1500-year climatic cycle during the Holocene, related to the glacial Dansgaard-Oeschger cycle, is a matter of intense debate. However, by introducing precise timing requirements it can be shown that the 1500-year cycle displayed in Northern Hemisphere glacial records is also observed in Holocene records from all over the world.

The cycle is most prominently displayed in oceanic subsurface water temperatures, Arctic atmospheric circulation, wind deposits, Arctic drift ice, and storminess records.

Histoire longue des cyclones aux Antilles

by Benoît Rittaud, 13 septembre 2017


Le cyclone Irma qui a dévasté Saint-Martin et Saint-Barthélémy dans les Antilles françaises a servi de prétexte à de nombreux commentateurs et journalistes pour en remettre une couche sur les « dérèglements climatiques d’origine humaine ». Comme d’habitude, les vagues éléments de prudence rappelant qu’on ne peut tirer de conclusions d’un élément isolé ont vite été noyés par les « appels à l’action » et l’invocation de l’Accord de Paris de 2015.

Or s’agissant du climat aux Antilles l’année 2015 a été importante pour une toute autre raison que la signature de l’Accord de Paris : c’est l’année de publication d’un article de recherche tout à fait passionnant sur les ouragans dans cette région du monde.

Evidence for Little Ice Age in Antarctica

by UC Santa Cruz Newscenter, August 31, 2017 in WUWT


Changes in the sources of nitrogen and the composition of the phytoplankton community are more likely to account for the differences seen in the isotope data, Huckstadt said. “It looks more like a shift at the base of the food web, probably related to the transition from the Little Ice Age to current conditions, causing changes in the phytoplankton community,” he said.

See also: « Here we present new data from the Ross Sea, Antarctica, that indicates surface temperatures were ~ 2 °C colder during the LIA, with colder sea surface temperatures in the Southern Ocean and/or increased sea-ice extent, stronger katabatic winds, and decreased snow accumulation. »

Climate-driven variability in the occurrence of major floods across North America and Europe

by Glenn A. Hodgkins et al., September 2017 in Journal of Hydrology


 

Trends in major-floods from 1204 sites in North America and Europe are assessed.

Trends based on counting exceedances of flood thresholds for groups of gauges.

The number of significant trends was about the number expected due to chance alone.

Changes in the frequency of major floods are dominated by multidecadal variability.

See also here

Quantifying climatic variability in monsoonal northern China over the last 2200 years and its role in driving Chinese dynastic changes

by J. Li, J. Dodson et al., March 1,  2017 in QuaternSciReviews


We suggest that solar activity may play a key role in driving the climatic fluctuations in North China during the last 22 centuries, with its quasi ∼100, 50, 23, or 22-year periodicity clearly identified in our climatic reconstructions.

We quantitatively illustrate that precipitation (67.4%) may have been more important than temperature (32.5%)…

Solar Cycle Continues To Be The Weakest In 2 Centuries

by  F.  Bosse and  F. Vahrenholt, August 23, in NoTricksZone


The sun was completely free of spots on 11 days in July. Notable: while during last month the sun’s northern hemisphere was more active (in June all sunspots were in the northern hemisphere), last month the southern hemisphere was the most active part with 60% of the sunspots appearing there. The following diagram shows the course of solar cycle 24 thus far (…)

Big data finds the Medieval Warm Period – no denial here

by Jennifer Marohasy, August 22, 2017


Our results show up to 1°C of warming. The average divergence between the proxy temperature record and our ANN projection is just 0.09 degree Celsius. This suggests that even if there had been no industrial revolution and burning of fossil fuels, there would have still been warming through the twentieth century – to at least 1980, and of almost 1°C.

Chinese Academy of Sciences : see here and here,  also here

Most of the Recent Warming Could be Natural

by Jennifer Marohasy, August 21, 2017


AFTER deconstructing 2,000-year old proxy-temperature series back to their most basic components, and then rebuilding them using the latest big data techniques, John Abbot and I show what global temperatures might have done in the absence of an industrial revolution.  The results from this novel technique, just published in GeoResJ, accord with climate sensitivity estimates from experimental spectroscopy but are at odds with output from General Circulation Models.