It’s official: For the past 12 months, the Earth was 1.5 degrees Celsius higher than in preindustrial times, scientists said Thursday, crossing a critical barrier into temperatures never experienced by human civilizations.
According to the European Union’s Copernicus Climate Change Service, the past 12 months clocked in at a scorching 1.52 degrees Celsius (2.74 degrees Fahrenheit) higher on average compared with between 1850 and 1900.
At some level, that’s not surprising — the past 12 months have been scorching, as a warm El Niño cycle combined with the signal of human-caused warming generated heat waves and extreme weather events around the globe.
“This El Nino maximum is riding on top of a base climate that is continuously warming due to climate change,” Andrew Dessler, a climate scientist at Texas A&M University, said in an email. “The combination of them is what’s giving us such hot global temperatures.”
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But does this mean that the world’s most famous climate goal is out of reach? Not ... exactly.
Here’s what you need to know:
Where did the 1.5 Celsius goal come from?
In the 2016 Paris climate agreement, almost 200 nations agreed to keep the global average temperature from exceeding 2 degrees Celsius (3.6 degrees Fahrenheit) above preindustrial levels — and to “pursue efforts” to keep it below 1.5 degrees Celsius. The latter addition largely came from pressure from small-island states, who are at risk of disappearing under rising seas if temperatures get much higher.
Scientists have shown that holding the temperature rise to 1.5C could mean the survival of coral reefs, the preservation of Arctic sea ice and less deadly heat waves.
Momentum has gathered around that more ambitious goal — even as carbon emissions continue to rise. Activists and environmentalists have chanted “1.5 to stay alive” and pointed out that emissions will have to be cut dramatically by 2030 to meet that target.
Does this mean we have missed the 1.5C climate goal?
No. There’s actually some disagreement about what exactly counts as breaching that threshold — but scientists and policymakers agree that it has to be a multiyear average, not a single 12-month period. Scientists estimate that without dramatic emissions reductions, that will happen sometime in the 2030s. But there could be other single years or 12-month periods that cross the line before then.
Can we still avoid passing 1.5C?
Most scientists say passing 1.5C is inevitable. “The 1.5-degree limit is deader than a doornail,” Columbia University climate scientist James Hansen said in a call with reporters late last year.
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Scientists and economists use complicated models to try to predict how fast the world can transition away from fossil fuels. The Washington Post analyzed 1,200 modeled pathways for the world to shift to clean energy and found that only four of them showed the world hitting the 1.5C target without substantially overshooting or using speculative technology (like large-scale carbon capture) that doesn’t yet exist. At this point, many experts believe that the economy is too stuck on fossil fuels to transition fast enough for 1.5 degrees.
Does that mean we’ll pass catastrophic tipping points?
That’s a more difficult question. Scientists don’t know exactly when certain tipping points — like the collapse of the Greenland ice sheet or the release of greenhouse gases from thawing permafrost — will occur. It’s very hard to predict and model these types of catastrophic changes.
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And 1.5C isn’t a magic threshold; it’s not as though as soon as we pass that number, Antarctic ice sheets will collapse and ocean circulations will grind to a halt. But one thing is certain: For every tenth of a degree of warming, tipping points are more likely. Two degrees is worse than 1.9 degrees, which is worse than 1.8 degrees, and so on.
And at each tenth of a degree, the infrastructure and systems that the world has built — electric grids, homes, livelihoods — will become more strained. Our modern world simply was not designed for temperatures this high. At some level, the final temperature of the planet isn’t what matters most. It’s where countries can actually get carbon emissions to zero — and stop contributing to future warming altogether.
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