Our Final Warning: Six Degrees of Climate Emergency

by Mark Lynas

When I started writing this book I thought that we could probably survive climate change. Now I am not so sure. As you will read in these pages, we are already living in a world one degree warmer than that inhabited by our parents and grandparents. Two degrees Celsius, which will stress human societies and destroy many natural ecosystems such as rainforests and coral reefs, looms on the near horizon. At three degrees I now believe that the stability of human civilisation will be seriously imperilled, while at four degrees a full-scale global collapse of human societies is probable, accompanied by a mass extinction of the biosphere that will be the worst on Earth for tens or even hundreds of millions of years. By five degrees we will see massive positive feedbacks coming into play, driving further warming and climate impacts so extreme that they will leave most of the globe biologically uninhabitable, with humans reduced to a precarious existence in small refuges. At six degrees we risk triggering a runaway warming process that could render the biosphere completely extinct and for ever destroy the capacity of this planet to support life.

The Keeling Curve is a useful reality check, one that cuts through all the noise and confusion of the climate and energy debates. Unlike the slopes of the huge volcano on which it is measured, the initially gentle upward curve gets steeper the higher you go. That means that the rate of CO2 accumulation in the atmosphere is steadily increasing, from roughly 1 ppm in the early years to about 2 ppm annually today. There is no visible slowdown, no sudden downwards blip, to mark the implementation of the Kyoto Protocol, still less 2009’s Copenhagen ‘two degrees’ commitment or the landmark Paris Agreement of 2015. All those smiling heads of state shaking hands, the diplomats hugging on the podium after marathon sessions of all-night negotiating – none of that actually made any identifiable difference to the Keeling Curve, which is the only thing that actually matters to the planet’s temperature. All our solar panels, wind turbines, electric cars, lithium-ion batteries, LED lightbulbs, nuclear plants, biogas digesters, press conferences, declarations, pieces of paper; all our shouting and arguing, weeping and marching, reporting and ignoring, decrying and denying; all our speeches, movies, websites, lectures and books; our announcements, carbon-neutral targets, moments of joy and despair; none of these to date have so much as made the slightest dent in the steepening upward slope of the Keeling Curve.