Chapter 2 - Natural Global Warming: Climate Change in ‘Deep Time’

Abstract

In this chapter I will consider the footprint that the geological part of the carbon cycle has had on the deep history of the Earth. Sedimentary rocks and unconsolidated sediments contain preserved elements of the ancient environments in which they were deposited through their sedimentary structures, fossils, isotopic and geochemical character. The layers of sedimentary rocks can essentially be ‘read’ and interpreted to identify cycles of warming and cooling spanning huge periods of millions of years. A few of the warming episodes have been severe enough to affect the continuity of life on Earth: for example at the Permian-Triassic boundary about 250 million years ago and at the Palaeocene-Eocene Thermal Maximum about 55 million years ago. These geological studies enable us to see climate change being acted out on a grand scale that simply is not visible to modern climate scientists. Its value is that you can see the broad sweep of change, or ‘the wood for the trees’. But deep-time climate change information has little value for the planners and policymakers that seek the short-term detailed and local information that can futureproof our society to climate change.