The CO2 – temperature relationship

Titre : The CO2 – temperature relationship

Laboratoire de rattachement : LGGE

Encadrant : Frédéric Parrenin

Téléphone : 0476824265

Co-Encadrant : Dominique Raynaud

Mots clés : Paleoclimatology, Antarctica, ice cores, chronology, greenhouse gases

Contexte et objectifs de la mission de stage :
It is at our time one of the most discussed physical relationship, not only in the scientific world, but also among the policy makers and the general public, given the planetary issues on the future of our climate (see for example the conference on climate at Paris in December 2015). The aim is to understand what is the sensitivity of the climate to a modification of the CO2 concentration in the atmosphere. Several approaches are possible to validate this relationship and its application to the future, in particular the coming century. Speaking of observations, we have the direct atmospheric measurements since approximatively 1850 (the so-called instrumental period) and we also have the climatic archives preserved in the marine, continental or glacial sedimentary layers. The glacial sediments from Antarctica allow reconstructing the atmospheric CO2 concentrations based on the air bubbles enclosed in the ice. It is a subject for which LGGE has acquired a strong expertise and reputation at an international level.
During the last deglaciation, approximatively 20,000 to 10,000 years ago, we have discovered that during this transition, CO2 and Antarctic temperature have varied in phase (Parrenin et al., 2013). This observation constitutes an important step toward the understanding of the sensitivity of climate to changes of atmospheric CO2. We now would like to use a mathematical method called wavelet decomposition (Mallat, 1989) which should allow to understand the phase relationship between CO2 and Antarctic temperature during various time periods. It should in particular allow to analyse how the phase relationship varies with the considered period, each periodicity being caracteristic of a certain class of climatic mechanisms.