Global carbon emissions were 58% higher in 2012 than they were in 1990. The atmospheric concentration of carbon dioxide has risen from just under 340 parts per million in 1980 to 400 in 2015. To stand a fair chance of keeping warming to just 2°C by the end of the century—the goal of global climate policy—cumulative carbon emissions caused by humans must be kept under 1 trillion tonnes. Estimates vary but, according to the Intergovernmental Panel on Climate Change, the total had hit 515 billion tonnes by 2011. Climate Interactive, a research outfit, reckons that if emissions continue on their present course around 140 billion tonnes of greenhouse gases will be released each year and temperatures could rise by 4.5°C by 2100. And even if countries fully honour their recent pledges, temperatures may still increase by 3.5°C by then.
The world is already 0.75°C warmer than before the Industrial Revolution….
Melting glacier ice, and the fact that warmer water has a larger volume, mean higher sea levels: they have already risen by roughly 20cm since 1880 and could rise another metre by 2100. That is perilous for low-lying islands and flat countries: the government of Kiribati, a cluster of tropical islands, has bought land in Fiji to move residents to in case of flooding. Giza Gaspar Martins, a diplomat from Angola who leads the world’s poorest countries in the climate talks, points out that they are particularly vulnerable to the effects of a warming planet. Money alone, he argues, will not fix their problems. Without steps to reduce emissions, he predicts, “there will be nothing left to adapt for.”…
For every 0.6°C rise in temperature, the atmosphere’s capacity to hold water grows by 4%, meaning storms will pour forth with greater abandon. The rains of the Indian monsoon could therefore intensify, cutting yields of cereals and pulses.
Climate change seems also to be making dry places drier, killing crops and turning forests into kindling. Forest fires in Indonesia, more likely thanks to the current El Niño weather phenomenon, could release 2 billion tonnes of carbon dioxide, about 5% of annual emissions due to human activity, says Simon Lewis of University College London. In recent months fires have swallowed more than 2.4m hectares of American forests. Alaska suffered 80% of the damage—a particular problem because the soot released in these blazes darkens the ice, making it less able to reflect solar radiation away from the Earth.
Developments in the Arctic are worrying for other reasons, too. The region is warming twice as fast as the rest of the world, a trend that could start a vicious cycle. Around 1,700 gigatonnes of carbon are held in permafrost soils as frozen organic matter. If they thaw, vast amounts of methane, which is 25 times more powerful as a global-warming gas than carbon dioxide when measured over a century, will be released. One hypothesis suggests that self-reinforcing feedback between permafrost emissions and Arctic warming caused disaster before: 55m years ago temperatures jumped by 5°C in a few thousand years…
And on September 29th Mark Carney, the governor of the Bank of England, warned that though measures to avoid catastrophic climate change are essential, not least for long-term financial stability, in the shorter term they could cause investors huge losses by making reserves of oil, coal and gas “literally unburnable”.
Excerpts from Climate Change: It’s Getting Hotter, Economst, Oct. 3, 2015, at 63