Séminaire EPOC "Magnitude and state dependency of (palaeo) climate variability"

Résumé :
Determining magnitudes of climate variability is important for attributing past and predicting future changes in climate. Multidecadal and longer temperature variability is poorly constrained, however, primarily because instrumental records are short and proxy records are noisy. Using a global compilation of Holocene marine temperature proxy records and correcting for non-climate variability, we derive an estimate for regional temperature variability between annual and millennial time-scales. Our estimate of temperature variability is consistent between different proxy types and with instrumental records. In comparison, general circulation model simulations have systematically less temperature variability than instrumental and proxy-based estimates. Discrepancies in variability are largest at low latitudes and increase with timescale, reaching two orders of magnitude for tropical variability at millennial timescales. In addition of knowing the magnitude of Holocene climate variability, there is also considerable interest in determining whether changes in the background state, such as the projected future warming, influence the variability. By contrasting the temperature variability estimated from records in the Holocene, the last glacial maximum and the Eemian, we show that there is a significant relationship between mean temperature and temperature variability. This relationship shows that warmer climates are more stable and might suggest a future with less overall climatic variations.