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Genetic Record of Atmospheric Carbon dioxidE (GRACE) (GRACE)
Start date: 01 Sep 2008, End date: 31 Aug 2015 PROJECT  FINISHED 

Two key variables, temperature and atmospheric carbon dioxide (pCO2), define the sensitivity of the Earth’s climate system. The geological record provides our only evidence of the past climate sensitivity of the Earth system, but there is no direct quantitative measure of pCO2 or temperature beyond the 650 kyr extent of the Antarctic ice cores. The reconstruction of past climate, on timescales of millions of years, relies on the analysis of chemical or isotopic proxies in preserved shells or organic matter. Such indirect approaches depend upon empirical calibration in modern species, without understanding the biological mechanisms that underpin the incorporation of the climate signal. The intention of this ERC grant proposal is to establish a research team to investigate the “living geological record” to address this major gap in climate research. I hypothesise that direct climate signals of the past are harboured within, and can ultimately be deciphered from, the genetic make up of extant organisms. Specifically, I propose an innovative approach to the constraint of the evolution of atmospheric pCO2 during the Cenozoic. The approach is based on the statistical signal of positive selection of adaptation within the genetic sequences of marine algal Rubisco, the notoriously inefficient enzyme responsible for photosynthetic carbon fixation, but supplemented by analysis of allied carbon concentrating mechanisms. As a calibration, I will characterise the biochemical properties of Rubisco in terms of specificity for pCO2, isotopic fractionation and kinetics, from a range of marine phytoplankton. The prime motivation is a history of pCO2, but the project will yield additional insight into the feedback between phytoplankton and climate, the carbon isotopic signatures of the geological record and the mechanistic link between genetic encoding and specific
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