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Chris Mooney @chriscmooney
, 19 tweets, 4 min read Read on Twitter
1. So in light of the really big news yesterday about Antarctic ice loss *tripling* in a decade, I wanted to further unpack what this means and why it is so significant. washingtonpost.com/news/energy-en…
2. As I reported yesterday, a major scientific assessment has confirmed that the continent is now losing 219 billion tons of ice per year from 2012-2017, and that is three times the ice loss for the period 2002-2007, or 10 years ago.
3. The study itself is here and the data on how the rate of ice loss has increased, over 5 year periods, is in table 1.
nature.com/articles/s4158…
nature.com/articles/s4158…
4. Key fact you need to know before we go any farther -- it takes about 360 billion tons of ice to produce a millimeter of sea level rise.
5. So based on that, with 219 billion tons a year, you’re looking at a little over half a millimeter per year of sea level rise right now. That's from Antarctica only; globally there’s much more than that.
6. There is certainly no guarantee that the tripling -- from just 73 billion tons per year 10 years ago -- will continue.
7. But just imagining what would happen if it did helps to underscore why scientists are watching Antarctica so closely -- and view it as the real wild card, and the one place that could make a big difference to sea levels in this century.
8. From current loss levels, another tripling would mean 657 billion tons per year, or close to 2 millimeters per year of sea level rise; another tripling on top of that would mean 1,971 billion tons per year, or over half a centimeter per year. And so on.
9. Let me underscore again – nobody is saying losses will continue to increase at this very fast rate.
10.But many scientists are indeed saying that Antarctica has the potential to lose a lot more ice than it is losing now.
11. After all, one key finding of the current assessment is that losses in East Antarctica – the biggest area, containing the most ice by far – are minimal at this point. For now.
12. There are also cases of past planetary deglaciation events where we know seas rose considerably faster than they’re rising now.
13.At the end of the last ice age, for instance -- and as I reported in a recent story -- it is believed that seas rose at a rate of “tens of millimeters annually.” washingtonpost.com/news/energy-en…
14. Granted, there were far bigger ice sheets in the Northern hemisphere at that time than there are today. It's not an exact comparison.
15. Another thing I didn't get to in the story, but wanted to mention as key context -- at 219 billion tons per year of losses, Antarctica is still actually lagging Greenland. Greenland is at 286. sealevel.nasa.gov
16. Greenland is melting faster right now because it is being subjected to rapid Arctic warming. But everybody knows that Antarctica has vastly more *potential* to lose ice than Greenland does.
17. The next thing to watch for, really, would be if Antarctica starts living up to that potential and surpasses the annual losses from Greenland.
18. It all underscores that right now, we are seeing a tripling in Antarctica and simply wondering if it is the beginning of something a lot bigger. We can’t say for sure that it is, or that the current rate of change will continue.
19. Nevertheless, the changes that have already happened are more than enough to make you stop and take notice. /end
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