What happens if the world warms up by 2°C?
"At a 2°C rise, people will begin to die of what is now considered normal summers. Countries already hit by hurricanes face ever greater storms. Plant growth slows down, then stops. Plants don’t absorb CO2 as efficiently, instead emitting it. The extra carbon sees global warming spiral out of control. In the year 2100 sea levels would rise by a meter displacing 10% of the world's population. In this 2°C future, ecosystems across the globe collapse. A third of all life on earth faces extinction."
What happens if the world warms up by 3°C?
"If global temperature rises by 2°C the chances of avoiding a 3°C increase are slim. At a 3°C increase plants stop absorbing CO2, enough carbon builds in the atmosphere to raise temperatures by another 1.5°C by 2100. The planet is tipped into runaway global warming. Cities and farms around the world will loose their rivers and reservoirs run dry. Saltwater creeps upstream and groundwater is poisoned. This tips food production into a irreversible decline."
What happens if the world warms up by 4°C?
"After the collapse of the amazon and the carbon cycle, stabilising the global temperature to avoiding a 4°C increase may no longer be possible. Coastal cities will either vanish or become islands. A sea level rise of 1m every 20 years is far beyond our capacity to adapt. At this point up to 85% of the amazon rainforest has disappeared. But the most damaging effect of this temperature is an irresistible thawing of permafrost. At least 500bn tonnes of carbon trapped below ground could be released by 2100."
What happens if the world warms up by more than that?
"Above 4°C we are looking at a vastly different world. Rainforests have turned into deserts and rising seas reach see into continents. Migrants force their way into the few habitable places left on earth. Civil wars are the inevitable outcome. To see what the world could look like at 6°C rise, we have to go back 251 million years. 95% of living species were wiped out. At sea everything suffocated. The forests are burning, the rivers are drying up. Continents carved up by toxic oceans and corpses pile up in cities across the planet. A 6°C world is a bleak one."