🧵Some things to watch for in tomorrow's IPCC report:
➡️Are 7.0/8.5 used as ref scenarios?
➡️Has central est of climate sensitivity gone up/down vs AR5?
➡️Does report venture into policy (eg, carbon budgets, Paris Agreement, etc)?
➡️Does D&A framework get tossed in favor of EA?
Importantly
AR6 WG1 will necessarily be less "alarmist" than AR5 (which wasn't that alarmist) simply bc RCP8.5 was centered in AR5 and we now know extreme scenarios (7.0/8.5) are implausible
Expect lots of excuses from IPCC observers for again focusing on extreme scenarios
I fully expect a lot of euphemisms to be used tomorrow for "reference scenario"
Like:
➡️high emissions scenario
➡️very high emissions scenario
➡️worst case scenario
➡️continued increasing emissions
Changing semantics won't change the underlying issues w/ implausible scenarios
When the IPCC reports its findings tmrw, it'd be great if they were to be asked a simple question by the media:
"How plausible are each of these scenarios?"
The answer of course is that the IPCC does not know the answer to this question because they have not addressed this Q!
SSP5-8.5 is absolutely thrilling
It doubles per capita coal global consumption from RCP8.5 to 6.2x that of ~2020
Who thinks global coal is going to increase by 6.2x pc by 2100? (Hint: Nobody!)
It is thus hugely misleading to report IPCC projections as a probability distribution
Eg, IPCC projects (say) 2100 sea levels to increase by 0.5m to 1.5m (I just made these up) where 0.5m is SSP1-2.6 & 1.5m is SSP5-8.5
This is reported as "SLR could increase by as much as 1.5m"
Including SSP5-8.5 outcomes in such distros is a way to launder implausible outcomes as plausible
1-scenario ranges aren't prob distributions
2-scenario ranges don't bound possible futures, in this example SLR could be lower or higher
3-scenarios ranges don't imply plausibility
So a word of caution to reporters & climate advocates
If you highlight, emphasize, promote top end findings of SSP5-8.5 or SSP3-7.0 (or let's hope not SSP3-8.5) you will be handing on a silver platter your political opponents (against climate policies) a gift of true hyperbole
And note that you cannot rescue SSP5-8.5 or SSP3-7.0 via semantics or by invoking hypothetical variables that might in the future compensate for their (already observed) departures from reality
Once you invoke new variables you've created a new scenario, which isn't 7.0 or 8.5!
Release of AR6 is important for climate policy/politics
But for those who know the literature already there won't be any science surprises
Reporting/interpreting will be a test of scientific integrity for scientists, reporters, politicians - I hope many pass the test 😎🙏
/END
PS. I should note that underlying this thread is a design flaw in the IPCC. The scenarios used by WG1 are provided to them by WG3. They are essentially a black box upon which to run climate models. WG1 authors (generally) are not experts in scenario development or plausibility.
PPS. I should add, for those new to these analyses, climate change is real, caused by humans & aggressive mitigation and adaptation policies make sense (as I've argued for decades)
None of that justifies bad or dated science or implementing corresponding course corrections! 🙏
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🧵Some might be curious why the IPCC focuses on the scenarios that it does
After all these scenarios are the foundation of the entire report's look to the future & assessment of possible impacts and the worth of different policy approaches . . .
The short answer is that the highest priority scenarios were selected for scientific purposes first & considerations of plausibility absent
Here is how the CMIP6 exercise justified its baseline (BAU/reference) scenarios
I'll be interested of course in how the IPCC WG1 treats scenarios but also, those reporters on the climate beat who are very well aware of these issues
Implausible scenarios of scary, alarming, extreme futures are often too enticing not to report on as predictions/projections
As I explained in The Climate Fix a decade ago, the core messages of the IPCC have remained largely unchanged since 1990, and I expect those messages to be reaffirmed by AR6 ... probably with better graphics and images
Those looking for radically new messages will be disappointed
This is a bit of an loaded question, since CMIP6 prioritized 7.0/8.5 scenarios (baseline aka BAU aka reference) so we should expect these to serve as reference scenarios (euphemisms: "high emissions," "4 deg C" or "emissions continuing to increase") in AR6
We shall see . . .
Does anyone know if full AR6 is released Monday or just SPM? I'd hope the whole thing
The science of advantage in both Pistorius & Leeper cases was substantially similar, notably the presence of an advantage could not be determined conclusively in either case (uncertainty & dueling experts!)