Archives par mot-clé : Holocene

New Paper: Northern Hemisphere Temperatures Rose 4–5°C Within ‘A Few Decades’ 14,700 Years Ago

By Kenneth Richard , April 2017


According to a new paper, the Bølling Warming event 14,700 years ago raised the surface temperature for the entire Northern Hemisphere by 4 to 5°C within a few decades.  This is a hemispheric warming rate of approximately 2.0°C per decade, which is 40 times faster than the 0.05 °C per decade global warming rate since 1850 (and 1998).

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.