Abstract

Interpretations of climate revolve about changes of atmospheric composition, which involve an increase of greenhouse gases. Carbon dioxide and methane are each emitted by human activities, as well as a host of native processes. Their relationship to global temperature is central to understanding current climate and how it will evolve.

Atmospheric composition and temperature are found to obey a clear two-pronged relationship in the proxy record from ice cores, which represents ancient changes that operate on time scales longer than several thousand years. A similar relationship is found to be obeyed in the observed record of actual atmospheric measurements, which represents modern changes that operate on time scales shorter than a century. Supporting analysis shows that the two relationships are connected. It reveals a common physical mechanism behind changes of composition in the two records. The physics common to the records provides unified insight into recorded changes of greenhouse gases, those apparent in the proxy record of ancient composition as well as those actually observed during the 20th century. The governing relationship is then compared against the relationship that prevails in climate models, in their simulation of future changes.