Fig. 3.

Growth biases of atmospheric CO₂ concentrations prognostically computed by emission-driven ESMs in the fifth phase of CMIP5. The growth bias in a given year t is calculated as C_m(t) − C_m(1901) – [C_o(t) – C_o(1901)], where C is atmospheric CO₂ concentration and the subscripts m and o denote model and observation, respectively. The reference baseline year is 1901 for which the growth bias is forced to be zero, allowing a focus on the long-term trend. The thick black bar indicates our estimated bias (∼17 ppm) caused by lacking explicit representation of mesophyll diffusion. Details about these ESMs and CMIP5 can be found elsewhere (21, 22).