Climate Stability and Policy: A Synthesis

TL;DR

This paper reviews Earth's climate history, emphasizing the recent stability of the current interglacial period and the limited impact of rising CO2 levels on delaying future glaciations, highlighting policy implications.

Contribution

It synthesizes climate history and assesses the influence of various forcings, emphasizing the limited effect of CO2 increases on glaciation cycles.

Findings

Current interglacial duration aligns with past periods.

Rising CO2 unlikely to delay next glaciation.

Climate sensitivity to small forcings is significant.

Abstract

During most of the Phanerozoic eon, which began about a half-billion years ago, there were few glacial intervals until the late Pliocene 2.75 million years ago. Beginning at that time, the Earth's climate entered a period of instability with the onset of cyclical ice ages. At first these had a 41,000 year cycle, and about 1 million years ago the period lengthened to 100,000 years, which has continued to the present. Over this period of instability the climate has been extraordinarily sensitive to small forcings, whether due to Milankovitch cycles, solar variations, aerosols, or albedo variations driven by cosmic rays. The current interglacial has lasted for some ten thousand years-about the duration of past interglacials-and serious policy considerations arise as it nears its likely end. It is extremely unlikely that the current rise in carbon dioxide concentration-some 30% since 1750, and projected further increase over the next few decades-will significantly postpone the next glaciation.