Climate change is a threat to all life on earth. Environmental activist and journalist Mark Lynas explains why global warming must not cross the 2ºC line.
Few of us would notice if the temperature went up by 2ºC tomorrow. Normal weather variations – cloud and rain one day, blue, sunny skies the next – can change the local daily temperature by ten or more degrees in a few hours.
In comparison, 2ºC seems like nothing. But 2ºC of global average change is a different matter altogether.
We measure our rising temperatures against figures from the mid-19th century – when wealthier countries started to industrialise in earnest. And there has been a global average temperature rise of 0.8ºC since the year 1850.
This change is enough to alternately drench the UK in floods and bake it in summer droughts, to consign the excitement of a white Christmas to history, and to raise sea levels around our shores so that land in East Anglia is already being abandoned.
The 0.8ºC global rise was enough to kill 30,000 elderly people across Europe in the 2003 heat wave, and to displace half a million New Orleans residents with an unusually fierce hurricane.
Nearly every mountain glacier on Earth is melting at an unprecedented rate. The Arctic has entered an unstoppable spiral of disappearing ice; it is probably already too late to prevent open water appearing at the North Pole.
Imagine, then, what 2ºC would do
Coral reefs would virtually disappear from the world’s oceans, eliminating marine ecosystems, and decimating fish stocks that can be economically and nutritionally vital to some poor people.
A 2ºC rise would tip the Greenland ice sheet into rapid and irreversible melt, raising sea levels faster even than scientists have projected. Low-lying islands such as Tuvalu and Kiribati would submerge, wiping out entire nations, and creating a new class of stateless climate refugees.
In Africa the disappearance of the last snows from Mount Kilimanjaro would eliminate both a tourist magnet and a source of water in one of the poorest parts of the world.
The elimination of glaciers in the Peruvian Andes would deprive tens of millions of people along the Pacific coast of freshwater. Without water, they too will become refugees.
Drought would destroy agriculture across sub-Saharan Africa, and malaria would migrate to new areas – again, particularly in poorer countries.
A third of life on Earth would face extinction in the worst mass die-off since the asteroid strike that killed the dinosaurs.
And we must look beyond the 2ºC rise
A chilling forecast. Yet the science suggests that, beyond the 2ºC line, there is a threat of runaway global warming. This is for three reasons.
Firstly, thawing Siberian permafrost – the world’s largest peat bog – would escalate methane production dramatically, pushing global temperatures higher still.
Secondly, researchers at the Hadley Centre of the UK Met Office have shown that 2ºC is likely to be the most the Amazonian rainforest can tolerate. If temperatures cross this line, the entire ecosystem will transform from lush, rain-fed (and naturally carbon neutralising) forest to a desert.
Add in the carbon in the world’s soils, which would also be released through warming, and temperatures could soar by an additional 1.5ºC – pushing the world way past the 3°C line.
So, we need to act now to save the planet
We have established that there are urgent reasons to act. And we can see that, since we will all face the consequences, we all – from our governments down to the man in the street – have a part to play.The question remains: how?
Again, the science is worrying. In order to retain a 75% chance of staying within the 2ºC safety zone and avoid runaway global warming, we need to stabilise atmospheric carbon dioxide concentrations at 400 parts per million (ppm). Currently they are at 382ppm and are rising at about 2ppm every year.
This gives us less than a decade to make serious cuts in global emissions.
If we miss this 400ppm target, and emissions go on rising, then the consequences are nothing short of terrifying.
A 450ppm concentration would give the world only a 30% chance of staying below the 2ºC line. Above this level anything is possible:
Drought and desertification could lead to most of southern Africa, much of the Mediterranean area and even parts of southern Europe becoming uninhabitable.
Increased conflict over water, food and other resources as hundreds of millions of people seek to resettle.
The west Antarctic ice sheet could begin to melt catastrophically, driving people away from coastal cities and deltas with an accelerated sea level rise of several metres.
And, as the world becomes warmer, methane hydrates from ocean beds would begin to erupt and the resulting global warming would eliminate most life from this planet.
There is still time – just – to avoid these nightmare scenarios, but only if we act fast, and globally.
Climate change needs to be at the top of each of our personal agendas, and finding equitable solutions to the problem needs to be the central focus of global politics.
Nothing less will save civilisation from the coming climate catastrophe.