Polar amplification of Pliocene climate by elevated trace gas radiative forcing
Peter O. Hopcroft, Gilles Ramstein, Thomas A. M. Pugh, Stephen J. Hunter, Fabiola Murguía‐Flores, Aurélien Quiquet, Yong Sun, Ning Tan, Paul J. Valdes
Abstract
Significance Warm periods in Earth’s history provide the only empirical evidence of how the climate system responds to raised atmospheric carbon dioxide (CO 2 ) levels. The Middle Pliocene, 3.3 to 3.0 My B.P., was the last time when CO 2 levels were as high as today. However, climate model simulations of the Pliocene underestimate the warming that has been reconstructed from geological archives. Using a numerical model of the global methane cycle we show that the inclusion of enhanced concentrations of non-CO 2 trace gases could have been responsible for an additional warming of 0.6 to 1.0 °C, with larger increases over northern land masses. These findings demonstrate the importance of trace gas climate forcing for both the Pliocene and potentially warm periods during much of Earth’s recent history.