Billions of climate refugees, extinction of most animal species on Earth and an unrecognisable planet.
- The devastating cost of climate change revealed
- 'Earth-shattering' new climate report reveals 2degC danger zone
Once considered worst-case scenarios, these apocalyptic outcomes are increasingly more plausible based on recent climate science.
Even if there were no further emissions from now, the United Nations reports the Arctic is now "locked into" a destructive degree of warming, with winter temperatures rising up to 8degC by 2080.
The global average temperature has so far only increased 1degC, but the effects are already severe. From a polar vortex in Chicago to record heatwaves in Canterbury, extreme weather events are becoming the rule instead of the exception.
In October last year, the UN released a special report warning that the Paris Accords' target of maximum 2degC warming would still be environmentally disastrous.
Erik Solheim, executive director of the UN Environment Programme, described the report as "a deafening, piercing smoke alarm going off in the kitchen. We have to put out the fire."
The report urged policymakers to instead aim for a maximum temperature rise of 1.5degC, a target requiring global greenhouse emissions to fall by almost half over the next decade.
Even the economic pathways for remaining under 2degC designed in the Paris Accords depend on carbon being directly removed from the atmosphere using technology which does not currently exist.
As of today, 80 percent more coal is burnt than in the year 2000, and the countries responsible for 80 percent of the world's greenhouse gas emissions are failing to meet self-imposed Paris Accord targets.
This currently puts the planet on a path to at least 4degC of warming by 2100.
Here's what that could look like.
Climate refugees
Past 4degC, equatorial land will start to become uninhabitable. In northern Africa, the average drought could last five years. This would displace vast populations, either within or across national borders.
Even at two degrees of warming, the UN estimates up to 50 million climate refugees by 2030 and 200 million by 2050. Highest estimates are up to 2 billion by 2100.
For perspective, at the peak of the European migrant crisis in 2015, approximately 1.3 million Syrians requested asylum in Europe.
Extinction of coral
Coral reefs act like rainforests for the ocean ecosystem, supporting up to 25 percent of marine species, despite making up less than 1 percent of the ocean floor.
However coral is particularly sensitive to temperature, becoming 'bleached' and dying as the sea warms. Over half the Great Barrier Reef is already dead and the chances of saving what remains are remote.
Even in the best case warming scenario of 1.5degC, approximately 70 percent of coral reefs will die. At the more plausible (but still very optimistic) 2degC, 99 percent of coral reefs will be extinct.
Based on current UN projections, catastrophic loss of biodiversity in the oceans is almost inevitable. But it isn't just the oceans in trouble - biologists estimate up to half of life on earth could face extinction by the end of the century.
Total carbon dioxide in the atmosphere and its potential effects
The concentration of atmospheric carbon currently hovers around 440 ppm, and we could reach 1200 ppm by 2100.
A recent experiment by climate scientists at the California Institute of Technology revealed at that carbon level, certain clouds may be unable to form, stripping Earth of a protective cooling layer.
Stratocumulus clouds act like arctic ice sheets, helping to keep the planet cool by reflecting sunlight back into space. Losing those clouds could add 8degC to global temperature rise, on top of the 4degC already projected, for a total of 12degC total warming.
At 12degC of warming, the Earth would be unrecognisable and largely uninhabitable to humans, returning to a climate last seen 55 million years ago in the Eocene period.
Back then crocodiles swam in the Arctic.
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