Showing papers by "David W. Lea published in 2012"

Making sense of palaeoclimate sensitivity

Abstract: Many palaeoclimate studies have quantified pre-anthropogenic climate change to calculate climate sensitivity (equilibrium temperature change in response to radiative forcing change), but a lack of consistent methodologies produces a wide range of estimates and hinders comparability of results. Here we present a stricter approach, to improve intercomparison of palaeoclimate sensitivity estimates in a manner compatible with equilibrium projections for future climate change. Over the past 65 million years, this reveals a climate sensitivity (in K W−1 m2) of 0.3–1.9 or 0.6–1.3 at 95% or 68% probability, respectively. The latter implies a warming of 2.2–4.8 K per doubling of atmospheric CO2, which agrees with IPCC estimates.

Millennial scale changes in sea surface temperature and ocean circulation in the northeast Pacific, 10–60 kyr BP

Abstract: [1] A new centennial-scale Mg/Ca temperature record from the California margin (ODP Site 1017E) reveals large millennial-scale oscillations between 10 to 60 kyr. This record indicates that sea surface temperature on the California Margin warmed rapidly on the deglacial by 7.4 ± 0.8°C, and was preceded by a pre-Bolling temperature oscillation of 2.6 ± 1.2°C. Millennial-scale events of the last glacial episode were marked by sea surface temperature oscillations of between 3 and 7°C on the California margin, and interstadials were associated with an increase in surface water salinity. The data are consistent with evidence for a glacial southward shift in the polar jet stream and concomitant strengthening of the relatively cold, fresh California Current during stadial events. The data also support previous hypotheses suggesting a tight coupling between the North Atlantic and northeast Pacific response to climate instability of the last glacial episode.