When the IPCC’s fifth assessment report was published in 2013, it estimated that such a doubling of CO2 was likely to produce warming within the range of 1.5 to 4.5°C as the Earth reaches a new equilibrium. However, preliminary estimates calculated from the latest global climate models (being used in the current IPCC assessment, due out in 2021) are far higher than with the previous generation of models. Early reports are predicting that a doubling of CO2 may in fact produce between 2.8 and 5.8°C of warming. Incredibly, at least eight of the latest models produced by leading research centres in the United States, the United Kingdom, Canada and France are showing climate sensitivity of 5°C or warmer.
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Even achieving the most ambitious goal of 1.5°C will see the further destruction of between 70 and 90 per cent of reef-building corals compared to today, according to the IPCC’s “Special Report on Global Warming of 1.5°C”, released last October. With 2°C of warming, a staggering 99 per cent of tropical coral reefs disappear. An entire component of the Earth’s biosphere – our planetary life support system – would be eliminated. The knock-on effects on the 25 per cent of all marine life that depends on coral reefs would be profound and immeasurable.
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But these days my grief is rapidly being superseded by rage. Volcanically explosive rage. Because in the very same IPCC report that outlines the details of the impending apocalypse, the climate science community clearly stated that limiting warming to 1.5°C is geophysically possible.
Past emissions alone are unlikely to raise global average temperatures to 1.5°C above pre-industrial levels. The IPCC report states that any further warming beyond the 1°C already recorded would likely be less than 0.5°C over the next 20 to 30 years, if all anthropogenic greenhouse gas emissions were reduced to zero immediately. That is, if we act urgently, it is technically feasible to turn things around. The only thing missing is strong global policy.