Other
Scientific paper
Dec 2008
adsabs.harvard.edu/cgi-bin/nph-data_query?bibcode=2008agufm.u33b..01l&link_type=abstract
American Geophysical Union, Fall Meeting 2008, abstract #U33B-01
Other
4901 Abrupt/Rapid Climate Change (1605), 4910 Astronomical Forcing, 4934 Insolation Forcing, 4946 Milankovitch Theory
Scientific paper
Astronomical theories of paleoclimate, e.g. the Milankovitch theory, explain the long-term variations of climate by the changes in the Earth orbit and position against the Sun, and consequently by the change in the distribution of the solar energy reaching the Earth. On the other hand, anthropogenic activities from early agricultural practices to more recent fossil fuel burning also impact climate change. Models, from conceptual ones to the most sophisticated general circulation models can be used to try to disentangle the contribution from human activity and the natural contribution in the record of climate change. Alternatively, a comparison of the climate records during past interglacials similar to the one we are living in can give some insight into the natural behaviour of the climate system during an interglacial. As far as the long-term climate change is mostly orbitally driven, we will search orbital and insolation time series for past analogues of the non-human perturbed Holocene. When doing so, some key questions must be answered. The first one is related to the time interval to be used as target. A previous study (Loutre and Berger, 2000) focused on the interglacial itself, assuming that the preceding deglaciation had a negligible impact on the interglacial. Rather we decided here to choose a target time interval that includes the deglaciation. Another question is related to the choice of the variable that will be used for correlation. It can be the orbital parameters themselves. It is also possible to use top-of-the-atmosphere insolation. If daily insolation is chosen, the latitude and time in the year for which it is computed are crucial; if a more time- integrated insolation is used (e.g. seasonal insolation), the time interval for the integration is an essential feature. Loutre and Berger (2000) used mid-June insolation at 65N and identified MIS11 as the most recent potential analogue for the future climate. A higher correlation of the insolation was even obtained between the future and MIS19. Here, we focus on the Holocene, starting from the last glacial maximum up to the next millennia (21 ka BP to 9 ka AP). There is a good correlation between the insolation changes during most of the recent interglacials and this target time interval, but the correlation can be poor for the orbital parameters taken separately, due to different leads and lags between the orbital parameters among the different interglacials. Namely, the maximum of eccentricity of the Holocene (14 ka BP) leads the minimum in climatic precession by 2 ka and the maximum of obliquity by 5 ka. At MIS5, the maximum of obliquity occurs 4 ka before the minimum in climatic precession and several thousands of years before the maximum of eccentricity. This rapid comparison underlines that certain interglacials are very poor analogues for the Holocene by reference to the astronomical parameters. A more systematic investigation confirms that no interglacial is displaying high correlations with the Holocene for all the astronomical parameters. For example, MIS11 shows as strong correlation with the present and future insolation (Loutre and Berger, 2000) but the correlation is much smaller for the orbital parameters. On the point of view of the orbital parameters, MIS15 might be the best compromise of the Late Quaternary. Loutre M.F. and Berger A. 2000. Future climatic changes: are we entering an exceptionally long interglacial? Climatic Change 46: 61-90.
Berger Adam
Crucifix Michel
Loutre Mf
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