Representatives from 195 countries are meeting in Paris this week, with plans in hand for reducing their carbon emissions. But even if all the countries actually meet their pledges (and there's no guarantee they will), will the promises work?
A team of environmental and public policy researchers took a stab at answering this question in a paper published in the journal Science last week. The team analyzed the Intended Nationally Determined Contributions, or INDCs, submitted by countries participating in COP21. As it turns out, humanity's ability to slow the Earth's warming depends a lot on what countries do after the INDC agreement is met, which only extends to 2025 or 2030. In other words, the INDCs are just first steps. For us to have a good chance of capping climate change at two degrees Celsius—the level of warming that experts consider manageable, but that's still expected to increase wildfires in the United States, put 20 to 30 percent of the world's species in danger of extinction, and melt the Arctic almost entirely—we'll need to keep working beyond the INDCs.
The research team used mathematical models to predict what would happen under several scenarios after 2030:
1. IF COUNTRIES DO NOTHING
It's basically guaranteed that the Earth will become more than two degrees Celsius warmer by 2100 than it was in the pre-industrial age. There would be more than a 50 percent chance of the Earth warming four degrees Celsius or more. Such a rise in global temperatures is expected to be catastrophic, causing "'major extinctions around the globe,' a 'reconfiguration of coastlines worldwide,' and further 'inundation of low-lying areas,'" as Ted Scheinman previously reported.
2. IF COUNTRIES KEEP THEIR INDC PROMISES, BUT FAIL TO INCREASE THEIR LEVELS OF CARBON CUTTING AFTERWARD
There would be less than a 10 percent chance humanity will be able to keep global warming at two degrees Celsius or lower. But there'd also be less than a 10 percent chance global warming will exceed four degrees Celsius. Most likely, warming will fall somewhere between those two numbers.
3. IF COUNTRIES KEEP THEIR INDC PROMISES, THEN RAMP UP THEIR EMISSIONS-CUTTING TO FIVE PERCENT A YEAR
Most likely, the world would warm between two and three degrees, but there would be about a 30 percent chance we could cap global warming at two degrees. There would be almost no chance of the world exceeding four degrees of warming.
These predictions show the INDCs are a good start, and could be the basis of helpful, long-term climate change mitigation. Even if nations actually keep their promises, we've still got a lot of work ahead.
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