Archives par mot-clé : Holocene

Greenland was nearly ice-free for extended periods during the Pleistocene

by JM Schaefer et al., Nature, December8, 2016

Here we show that Greenland was deglaciated for extended periods during the Pleistocene epoch (from 2.6 million years ago to 11,700 years ago), based on new measurements of cosmic-ray-produced beryllium and aluminium isotopes (10Be and 26Al) in a bedrock core from beneath an ice core near the GIS summit.

Modern ‘Warmth’ A Brief Excursion From 8,000-Year (Continuing) Cooling Trend

by Kenneth Richard, March 20, 2017

According to an estimate of global sea surface temperature (SST) changes during the last 2,000 years (“Robust global ocean cooling trend for the pre-industrial Common Era“), the addition of the last 2 centuries (1800 to 2000 C.E.) of relatively modest SST warming only changes the overall per-millennium global cooling trend (~0.4°C) by one tenth of one degree.  In other words, using a long-term perspective, the Holocene cooling trend has continued largely uninterrupted during the last two centuries.

Ice age thermostat prevented extreme climate cooling

Universitat Autònoma de Barcelona, March 14, 2017
from E. D. Galbraith, S. EgglestonA lower limit to atmospheric CO2 concentrations over the past 800,000 yearsNature Geoscience, 2017

During the ice ages, an unidentified regulatory mechanism prevented atmospheric carbon dioxide concentrations from falling below a level that could have led to runaway cooling, reports a team of researchers. The study suggests the mechanism may have involved the biosphere, as plants and plankton struggled to grow under very low carbon dioxide levels.