SPRATT. David Spratt (co-author with Phillip Sutton of “Climate Code Red” ) (2015): “2oC target is not safe. We have already crossed dangerous climate tipping points at just 0.8°C warming. In the words of former senior Obama advisor John Holdren in 2008: “the world is already experiencing ‘dangerous anthropogenic interference in the climate system”.21 Evidence includes:
• At less than 1°C of warming, West Antarctic glaciers are in “unstoppable” meltdown for 1-4 metres of sea-level rise.22
• Arctic tipping points have been crossed 23 for sea-ice-free summer conditions, with severe consequences for the future stability of permafrost and frozen methane stores, sea-levels rises, as well as accelerated global warming as ice sheets retreat and the Earth’s albedo (reflectivity) decreases.
• Extreme weather events are being made worse, with record heat and drought such as in California at present, and more intense cyclones including Superstorm Sandy and Typhoon Haiyan, both of whose impacts had a climate-warming component.
• The paleoclimate record also tells us that even the current level of CO2 (without accounting for 75 ppm of non-CO2 greenhouse gases we have added to the atmosphere) is enough for 3°C or more of warming at equilibrium:
• During middle Miocene, 16-14 million years ago, when temperatures were ~3 to 6°C warmer and sea levels 25 to 40 metres higher than at present, the CO2 level was similar to modern levels (between 350 and 400 ppm).24
• In the early-to-mid Pliocene, 5–3 million years ago, temperatures were 3°C above pre-industrial and CO2 levels were 360-400 ppm, very similar to today. The northern hemisphere was free of glaciers and ice sheets, beech trees grew in the Transantarctic Mountains and sea levels were 25 metres higher.25 There is also a variety of evidence that 2°C is not safe target for significant planetary systems:
• An estimated tipping point for Greenland Ice Sheet is 1.6°C (with an uncertainty range of 0.8 to 3.2°C).26
• Preserving more than 10% of coral reefs worldwide would require limiting warming to below 1.5°C (range: 1.3–1.8°C).27
• 1.5°C appears to be something of a tipping point” for extensive permafrost thaw. 28
In the first few months of 2015, new lines of evidence have been published suggesting that more elements of the system may be heading towards tipping points or experiencing qualitative change, including: the slowing of the Atlantic conveyor likely linked to climate change;29 accelerating ice mass loss from Antarctic ice shelves;30 the vulnerability of East Antarctica glaciers;31 declining carbon efficiency of the Amazon forests 32 and other sinks; 33 accelerated ice-mass loss from the Greenland Ice Sheet; 34 rapid thinning of Arctic sea-ice; 35 a new record low winter maximum for Arctic sea-ice extent; 36 the vulnerability of Arctic permafrost; 37 and the origins and possible proliferation of Siberian methane craters. In reality, 2°C is in fact the boundary between dangerous and very dangerous climate change, and 1°C warmer than human civilisation has ever experienced… In the lead up to the forthcoming Paris talks, policy makersthrough their willful neglect of the evidence are in effect normalising a 2.5–3°C global warming target. It’s time to “do the math” again. Effective policy making can only be based on recognising that climate change is already dangerous, and we have no carbon budget left to divide up. Big tipping-point events irreversible on human time scales and large-scale positive feedbacks are already occurring at less than 1°C of warming. It is clear that 2°C of climate warming is not a safe cap. ” (pp 6, 7, David Spratt, “Recount. It’s time to do the math again”, Breakthrough (National Centre for Climate Restoration), Melbourne, 2015: http://media.wix.com/ugd/148cb0_bb2e61584dbb403e8e33fd65b1c48e30.pdf ).