My current research is focused on the study of a set of contrasting warm periods in the recent geological past, each characterized by a different combination of seasonality, global average temperature, greenhouse gas concentration and land-ice albedo effects. The main objective is to determine how the radiative forcing provided by CO₂ during warm climate regimes of varying intensity has been linked (or not) to different aspects of global climate, including in particular changes in sea level, ocean circulation, deep ocean temperature and deep water carbonate chemistry. It seeks not only to “calibrate” climate forcing and response in the past, but also to understand the feedback mechanisms that have been at work, with the ultimate aim of assessing the variability of Earth system climate sensitivity. This is being attempted by means of geochemical analyses in two deep-sea sediment cores, one from the Atlantic sector of the Southern Ocean (core MD07-3077, 44º09’ S, 14º13’ W; 3770 m), a strategic region of the global ocean for the study of the global carbon cycle and its influence on climate sensitivity, and the other from the Iberian Margin in the Northeast Atlantic (core MD01-2443, 37º53’ N, 10º11’ W; 2925 m).

    Of the four interglacial warm regimes that have occurred during the last 450,000 years, I am mostly focused on Marine Isotope Stage (MIS) 7, the penultimate interglacial happening from 245,000 to 190,000 years ago, and MIS 11, the interglacial that occurred around 400,000 years ago. The mismatch between insolation forcing and climate response during these two interglacials exemplifies the non-linearity of the astronomical theory of ice ages, and underlines the importance of strong positive “internal” feedbacks in the climate system, that will have contributed to the different character of past warm periods.