2° C (3.6°F) - What does it mean?
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In 2015, the 196 nation signatories to the Paris Agreement, committed to keeping the mean rise in global temperatures below 2° C (3.6° F) above pre-industrial levels and preferably limit any increase to 1.5° C (2.7° F). Although there is nothing magical about the 2° figure, it is not a meaningless number.
“…[I]t would be wrong to infer that two degrees was just plucked from thin air, cautions Michael Mann, director of the Penn Center for Science, Sustainability and the Media at the University of Pennsylvania.
‘Clearly there is no absolute threshold,’ he says. ‘It’s more a somewhat objective definition of where we move from ‘bad’ into ‘really bad’ territory. Two degrees Celsius is a reasonable dividing line where we cross into the ‘red’ across all areas of concern.’
‘Well, 1.2°C warming, which is where we are, is too much,’ says Mann. ‘We’re already seeing devastating consequences. So, it’s really a question of just how bad we’re willing to let it get. 1.5°C would be bad, two degrees really bad, and three degrees is perhaps, as I argue in my new book Our Fragile Moment, civilization ending.’
Mann notes that a 2018 Intergovernmental Panel on Climate Change (IPCC) report found that the difference between 1.5°C of warming and two degrees could be devastating.
‘Basically, what it shows is that the additional 0.5°C of warming would likely mean the loss of Arctic sea ice, three times as much extreme heat, far greater levels of extinction and the possible loss of coral reefs across the planet. It would take us even closer to the tipping points for loss of Greenland and West Antarctic Ice Sheets (and the meters of sea level rise that go with it). Pretty stark stuff,’ he says.
Additionally, of course, an average global increase is just that— an average. Some places, such as the Arctic, are warming four times more quickly than the rest of the planet; what may seem like a moderate amount of sea level rise in parts of the United States, could be catastrophic in low-lying Pacific Island states.
For that reason, such states have been at the forefront of emphasizing the importance of limiting warming to 1.5°C. …”
What's the big deal about Earth getting 2° hotter? Kieran Mulvaney, National Geographic, December 1 2023
