title: Narrowing the spread in CMIP5 model projections of air-sea CO2fluxes.
abstract: Large spread appears in the projection of air-sea CO2fluxes using the latest simulations from the Coupled Model Intercomparison Project Phase 5 (CMIP5). Here, two methods are applied to narrow this spread in 13 CMIP5 models. One method involves model selection based on the ability of models to reproduce the observed air-sea CO2fluxes from 1980 to 2005. The other method involves constrained estimation based on the strong relationship between the historical and future air-sea CO2fluxes. The estimated spread of the projected air-sea CO2fluxes is effectively reduced by using these two approaches. These two approaches also show great agreement in the global ocean and three regional oceans of the equatorial Pacific Ocean, the North Atlantic Ocean and the Southern Ocean, including the average state and evolution characteristics. Based on the projections of the two approaches, the global ocean carbon uptake will increase in the first half of the 21stcentury then remain relatively stable and is projected to be 3.68-4.57 PgC/yr at the end of 21stcentury. The projections indicate that the increase in the CO2uptake by the oceans will cease at the year of approximately 2070.
authors.affiliation: Ministry of Education Key Laboratory for Earth System Modeling, Center for Earth System Science, and Joint Center for Global Change Studies (JCGCS), Tsinghua University, Beijing 100084, China.
authors.forename: Lei
authors.initials: L
authors.lastname: Wang
authors.affiliation: Ministry of Education Key Laboratory for Earth System Modeling, Center for Earth System Science, and Joint Center for Global Change Studies (JCGCS), Tsinghua University, Beijing 100084, China.
authors.forename: Jianbin
authors.initials: J
authors.lastname: Huang
authors.affiliation: Ministry of Education Key Laboratory for Earth System Modeling, Center for Earth System Science, and Joint Center for Global Change Studies (JCGCS), Tsinghua University, Beijing 100084, China.
authors.forename: Yong
authors.initials: Y
authors.lastname: Luo
authors.affiliation: Ministry of Education Key Laboratory for Earth System Modeling, Center for Earth System Science, and Joint Center for Global Change Studies (JCGCS), Tsinghua University, Beijing 100084, China.
authors.forename: Zongci
authors.initials: Z
authors.lastname: Zhao