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Smog in Beijing.
We are running out of time to prevent catastrophic effects of climate change from reshaping our world.
That's the message of the latest report by the Intergovernmental Panel on Climate Change (IPCC), which found that the world will start to experience some of the most severe effects of climate change once the planet warms 1.5 degrees Celsius over pre-industrial temperatures.
Human activity has already caused Earth's temperature to rise about 1 degree C, and another half-degree will make the effects we're already seeing much worse. Drought-prone regions will be much more likely to experience severe drought, and areas prone to heat waves or intense hurricanes will get more of those disasters, too. As glaciers melt and oceans expand, seas will continue to rise. These factors could trigger huge migrations of people and mass extinctions of animals. Most coral reefs will die, which could trigger rippling effects throughout the oceans.
Nations around the world pledged in the Paris agreement to try to prevent temperatures from rising more than 2 degrees by 2100. But this latest IPCC report found that the world is likely to cross the 1.5 degree barrier by 2040, with more than 3 degrees C of warming possible by 2100.
Preventing the world from crossing into that danger zone is still possible, but it'd require immense changes that are politically and practically unlikely. We'd have to cut greenhouse gas emissions 45% by 2030 compared to what they were in 2010. By 2050, we'd have to reduce emissions to zero.
Doing that would require an immediate, massive, coordinated transformation of the global economic system - especially the energy system - on a scale the world has never seen, the report authors said.
Since there's almost no chance of that happening, the world may resort to forms of geoengineering: implementing technologies that could modify Earth's atmosphere, seas, or skies in an attempt to cool the planet.
"Nothing suggests world will come close to meeting this goal on climate change," Richard Haass, the president of the Council on Foreign Relations, said on Twitter. "There is no US leadership, and the phrase 'international community' is more rhetoric than reality. We'd better set aside $ for adaptation and accelerate R&D on geoengineering."
No geoengineering technologies are ready yet for widespread use, and some of the methods are highly controversial - some experts even think their use could lead to global war. But the IPCC and other global organizations expect we'll need to resort to geoengineering to some degree.
Here's how humanity might try to transform the planet in order to survive.