Lynas, Mark – Six Degrees: Our Future on a Hotter Planet (2007)
Category: global warming, collapse; Rating: 5/5
Summary: Six Steps to Hell (Mark Lynas) 2007; Six Degrees Review (Real Climate) 2007; What will Climate Change do to our Planet? (Times) 2007
No-one disputes the denier argument that greenhouse gases are essential for life on Earth. But there is such an concept as too much of a good thing. It is ostrich-like to deny that our CO2 emissions, proceeding at rates unprecedented in geological history, will not soon lead to substantial global warming – current atmospheric CO2 levels were last seen during the Pliocene, when average global temperatures were almost 3C hotter. And it is Pollyannish in the extreme to maintain that the effects on human societies will be anything other than deleterious. In this book, Mark Lynas shows us why.
Basing his work on the IPCC’s projections of 1.4-5.8C of warming for the 21st century, Lynas reviews the existing scientific literature as to the effects each degree of global temperature rise will have on our biosphere. To appreciate the scale of the upper range of these projections, consider that global temperatures were around 6C lower during the depths of the last Ice Age – when the North Sea was dry land, desiccation affected even the tropics and massive ice sheets descended into central Europe, transforming it into a polar desert blasted by ice dust-laden winds.
In contrast to the conservative IPCC’s conception of climate change as gradual, he shows that there exist numerous positive feedbacks that will reinforce and accelerate global warming after the world warms by 2C – acidifying oceans will cease functioning as carbon sinks; the melting of polar ice will reduce the Earth’s albedo, making it more heat-absorptive; dying vegetation, including a possible Amazonian conflagration, will transform the world’s biomass from a carbon sink to a carbon source; melting Siberian permafrost will release previously trapped methane into the atmosphere, a greenhouse gas twenty times as powerful as CO2. Furthermore, anthropogenic global warming is occuring at rates unmatched in geological history as industrial civilization belches out carbon sequestered over tens of millions of years in decades, even as much of the world’s traditional balancing mechanisms – forests, biodiversity, mangroves, etc – have come under sustained human assault. Nor does it help that both paleo-climate reconstructions and new models taking into account the “dimming” effect of human aerosol emissions indicate that the climate’s sensitivity to CO2 levels is as much as twice higher than previously thought. All this sets the stage for a massive extinction event by the time temperatures rise by 6C, as the world’s oceans turn anoxic, seabed methane hydrates are released and lethal hydrogen sulphide bubbles into the atmosphere from the dead seas, even destroying the ozone layer in the process.