Sentences with phrase «isotope records based»

Not exact matches

In both cases the climate records are based on oxygen isotope measurements on datable layers of ice or stalagmite cave deposition.

Based on the temperature minimum recorded from the early Late Oxfordian of Kachchh, it was suggested that the widening of the Trans - Gondwanan Seaway may have led to increased upwelling in the Malagasy Gulf and to a cooling recorded in the oxygen isotopes of belemnites and other marine invertebrates from Kachchh [38].

''... worked with two sediment cores they extracted from the seabed of the eastern Norwegian Sea, developing a 1000 - year proxy temperature record «based on measurements of δ18O in Neogloboquadrina pachyderma, a planktonic foraminifer that calcifies at relatively shallow depths within the Atlantic waters of the eastern Norwegian Sea during late summer,» which they compared with the temporal histories of various proxies of concomitant solar activity... This work revealed, as the seven scientists describe it, that «the lowest isotope values (highest temperatures) of the last millennium are seen ~ 1100 - 1300 A.D., during the Medieval Climate Anomaly, and again after ~ 1950 A.D.» In between these two warm intervals, of course, were the colder temperatures of the Little Ice Age, when oscillatory thermal minima occurred at the times of the Dalton, Maunder, Sporer and Wolf solar minima, such that the δ18O proxy record of near - surface water temperature was found to be «robustly and near - synchronously correlated with various proxies of solar variability spanning the last millennium,» with decade - to century - scale temperature variability of 1 to 2 °C magnitude.»

«The solar and volcanic forcings we use are derived from reconstructions based on proxy data and are therefore also subject to considerable uncertainties, although recent explosive volcanic eruptions are likely to have cooled climate, and independent records of solar activity levels inferred from the cosmogenic isotope 10Be (43) and geomagnetic records (44) provide support to reconstructions (22, 45) that show generally increasing solar activity during the 20th century (12).»

The stratigraphic framework and related age models of the four sediment cores used in this study, are based on oxygen isotope stratigraphy, 10Be stratigraphy, paleomagnetostratigraphy, biostratigraphy, lithostratigraphy, and / or magnetic susceptibility records (Supplementary Figs. 2 — 5).

Global solar irradiance reconstruction [48 — 50] and ice - core based sulfate (SO4) influx in the Northern Hemisphere [51] from volcanic activity (a); mean annual temperature (MAT) reconstructions for the Northern Hemisphere [52], North America [29], and the American Southwest * expressed as anomalies based on 1961 — 1990 temperature averages (b); changes in ENSO - related variability based on El Junco diatom record [41], oxygen isotopes records from Palmyra [42], and the unified ENSO proxy [UEP; 23](c); changes in PDSI variability for the American Southwest (d), and changes in winter precipitation variability as simulated by CESM model ensembles 2 to 5 [43].

c) Average sunspot number prediction by a low - frequency modulation model (dotted curve) based on frequency analysis from sunspot and cosmogenic isotope records, compared to the average sunspot number since 1750 (continuous curve).

The modulation potential used in the calculations is based on the composite of data determined from the cosmogenic isotope records of 10Be and a neutron monitor.

Hansen's climate analyses have been based not only on the very basic physics that goes into climate model design, but on the detailed studies of the geological ice core and isotope records that are used to constrain and confirm climate model sensitivity.