letters to the editor

摘要

We do not discuss models but focus on experimental data reports from refereed journals. That existing data indicate that, starting long before humans appeared on Earth, our planet has experienced many alternate warming and cooling cycles, with corresponding maxima and minima in greenhouse gas concentration; CO_2 sometimes rose over five times our current concentrations before falling. Thermal cycles, including the MWP and LIA, have continued into current times, independent of human influence. Considerable data suggest that Earth has natural ways of first limiting excess temperature excursions and then recovering from them.