Thread by @chriscmooney

1. Many of the things in the new @IPCC_CH report on the oceans and cryosphere, we knew about already.

But the ones we didn’t know – not that they weren’t known by scientists, but they haven’t gotten much attention….a few of them are stunners.

washingtonpost.com/climate-enviro…

2. Here’s what we already know. We already know that pretty much everything frozen around the globe – glaciers, sea ice, permafrost, ice sheets – is melting or thawing.

3. Here’s what we also know. We know that the seas are losing oxygen and getting more acidic. We know that they’re rising and getting warmer.

4. But what’s striking about the @IPCC_CH report is what it says about the rapidity with which all of this is feeding into severe impacts.

5. Here, at least two parts of the report really stand out.

6. The first involves ocean heatwaves. While the warming of the global ocean overall is relatively slow and steady, it turns out the risk of extreme ocean heat events escalates much more rapidly.

7. This means that the majority of these heatwaves are already attributable to climate change – and that they’re poised to get 20 to 50 times more frequent compared with preindustrial occurrences by the end of the century.

8. To me, that is very dramatic finding. These events can be disastrous for marine ecosystems. This is what kills the coral and the kelp and in some cases lots of fish.

9. I don’t think many people (outside of the science world) realized that the level of ocean warming that we have so far translates into such severe events already -- or just how much more severe these will get.

10. There’s something closely related in the report about sea level rise. Yes, seas are rising slowly and steadily, just as the ocean is warming steadily.

11. But the implications along coastlines are not necessarily so slow and steady.

12. The report finds that the traditional “100 year storm” becomes a 1 year storm in many locations by the year 2050 -- and that’s even in the lowest emissions scenario, RCP2.6.

13. To be clear -- nobody talks about any scenario in which we emit less than in RCP2.6. RCP2.6 is the scenario you want to follow if you are trying to limit warming a lot. It is far from clear that we are going to be anywhere near it.

14. But what the @IPCC_CH is saying is that even in this low warming scenario, flooding risks go up sharply along many coastlines in the next few decades.

15.In sum: Averaging out all the wrinkles and differences across the planet, we see a rate of change on the order of slivers of a degree C and 3-4 millimeters per year for warming and sea level rise, respectively.

16. And that may sound slow. It may sound gradual.

17. But it leaves out some critically important things.

18. One is that the temperature change is highly concentrated and amplified in some geographic areas, as our 2C series is demonstrating.
washingtonpost.com/graphics/2019/…

19. The same goes for sea level change, which is also very unevenly distributed.

20. Meanwhile, when it comes to extreme events, for either sea level or ocean heat, a seemingly gradual background change can still really up the odds. And it is in these events that the real damage occurs.

21. To me, that’s one of the biggest takeaways from this report -- and why, read carefully, it contains such dramatic, striking findings. /end

Oh and by the way -- you can read the @IPCC_CH report yourself here ipcc.ch/srocc/download…