The powerful fiddle while world burns

Four years ago, it was Paris; for the next fortnight, it is Madrid. The scenery changes but the message does not: the world is running out of time to halt catastrophic climate change.

The efforts made to honour the 2015 Paris pledge to limit the rise in global average temperature to under 2°C, and ideally 1.5°C, above the preindustrial average have been “utterly inadequate”, according to the UN secretary-general.

António Guterres, speaking in Spain ahead of the COP25 climate summit to negotiate an emissions trading system, warned that the Earth is belching its way towards a “point of no return”. He blamed politicians for continuing to subsidise fossil fuels and refusing to tax pollution.

Perhaps Guterres had caught sight of an article, published last week in the journal Nature, speculating whether the planet has already reached a critical state of warming and is now, climatically speaking, doomed. The analysis of nine climate “tipping points” concludes we are in a “planetary emergency”, and possibly heading towards a hothouse Earth.

While some climate dangers, such as the runaway melting of ice sheets, have been historically predicted to happen if global average temperatures rise by 5°C, later models have lowered some of those margins to 1°C-2°C.

Worse, the tipping points might interact with each other in unknown ways to threaten a global cascade of irreversible harm. “If damaging tipping cascades and a global tipping point cannot be ruled out, then this is an existential threat to civilisation,” writes Timothy Lenton, director of the Global Systems Institute at the University of Exeter, who collaborated with academics in Germany and Denmark.

From a risk management perspective, they urge immediate political and economic action to keep the rise to below 1.5°C.

A tipping point is defined by the Intergovernmental Panel on Climate Change (IPCC) as a “large-scale discontinuity” in one piece of the Earth’s climate. Interrelated pieces include familiar totems such as Arctic sea ice and the Amazon rainforest. Less well-known components include the Atlantic Meridional Overturning Circulation, a “conveyor belt” that shifts warm water from the tropics northwards and brings deeper, colder water back south; and boreal forests, the evergreen thickets that ring northern latitudes and which sometimes sit atop permafrost and act as a vast carbon store.

In practice, a tipping point is a threshold beyond which a small tweak can have abrupt, irreversible effects. components of the world Some’ s climate, the researchers suggest, seem closer to the brink than others. The Greenland ice sheet may be nearing a point after which it will inexorably shrink. The loss of Arctic sea ice is another potential flashpoint: ice is more reflective than dark seawater, so melting ice fuels more heat absorption and warming.

Both phenomena might already be feeding instability into the system, by pushing more water into the North Atlantic and slowing down the conveyor belt. In turn, a sluggish circulation might, by interfering with the West African monsoon, trigger a drought in the Sahel region of Africa. Subsequent knock-on effects include a warmer Southern Ocean, which could accelerate ice loss in Antarctica.

Once the climate dominoes start falling, the risks become twofold: not only is there a slowdown in mopping up continued emissions but the planet could also begin burping out the carbon already locked away. Permafrost emissions, for example, could inject 100 gigatons of carbon dioxide into the atmosphere. That is three

CO2 emissions years’ worth of

(a record 33.1Gt was emitted globally in 2018, according to the International Energy Agency).

THE DELAY WITH DECARBONISATION MIGHT LEAD US TO DITHER OURSELVES INTO A CATASTROPHIC FUTURE

Not everyone is fully behind the apocalyptic analysis. “Greenland ice sheet collapse is pretty improbable at 1.5°C warming, or it would take centuries to melt, so it wouldn’t fit with a reader’s perception of a tipping point,” warns Piers Forster, professor of physical climate change at Leeds University and an IPCC author.

But Forster does agree that the delay with decarbonisation might lead us to “dither ourselves into a catastrophic future. As the world warms, we’ll need to spend more and more coping with the risks and adapting to a warmer future, with appropriate flows of money from global North to global South. This would take the wealth and capacity out of societies that are trying to get to net zero. If this happens, we would see a catastrophe.”

Not apocalypse, then, but catastrophe: the language changes but the message does not. /©