Fascinating new paper by @AndrewDessler and colleagues arguing committed warming might be higher than expected given historical pattern effects. Its combining a lot of different concepts together, so lets spend some time disentangling them https://t.co/ILi5z515Qy

A thread: 1/19

The paper's headline number is that we previously thought the world was committed to 1.3C warming, but that number is actually over 2C (> 1.5C by 2100). This is quite a different message than we get from Earth System Models, which suggest committed warming is only ~1.2C. 2/19
This would imply that the 1.5C by 2100 target is effectively impossible, and that long-term warming of >2C would be very difficult to avoid. However, the devil is in the details, and the picture is not quite as dire as it would seem at first glance. 3/19
When we talk about "committed warming" folks are generally talking about one of two scenarios: either constant CO2 and other GHG concentrations (and forcings), or getting all emissions (or just CO2 emissions) down to zero immediately. 4/19
In the first method – constant concentrations – we find that the world warms up another 0.5C or so, as the oceans continue to take up heat as more energy is being trapped by greenhouse gases than is being emitted back to space. Much of this additional warming happens by 2100 5/19
In the second method – zero emissions – atmospheric concentrations of CO2 start to fall, as the ocean and land continue taking up some of the CO2 that humans have previously emitted. 6/19
(short-lived greenhouse gases like methane are also quickly removed from the atmosphere, but so are short-lived aerosols that tend to cool the planet. To a first order approximation these cancel eachother out, though there are some temporal differences). 7/19
Falling atmospheric CO2 causes enough cooling to balance out the warming "in the pipeline" due to slow ocean heat uptake, and global temperatures remain relatively flat after net-zero emissions are reached. 8/19
This flat-temperatures-at-zero-emissions finding is quite robust, first appearing in Matthews and Caldeira in 2008, highlighted in the IPCC SR15, and more recently being found in 18 different Earth System Models in the CMIP6 ZECMIP: https://t.co/DjRn4f9MiC 9/19
What Dessler and colleagues look at in the new paper is the constant concentration scenario rather than the zero emission scenario, so its hard to directly compare the two. 10/19
Furthermore, their two numbers (1.3C vs 2C+ committed warming) conflate two different factors: higher climate sensitivity and changing warming patterns over time. 11/19
Modern climate models expect more then 1.3C warming at equilibrium in a constant concentration scenario. Rather, at 2.2 w/m^2 constant forcing they would expect around 1.7C warming (assuming a 3C ECS). 12/19
The 1.3C number in the paper is based on an observational-derived ECS of ~2C per doubling CO2, while the > 2C number is based on a revised ECS estimate of ~3.5C plus warming due to pattern effects. 13/19
Pattern effects themselves are a bit complicated. In short, climate models expect both the Western and Eastern Pacific Ocean to have similar rates of long-term warming. However, in the real world the Western Pacific is warming a lot faster than the Eastern. 14/19
Warming in the western Pacific tends to generate a lot more low-altitude clouds that reflect light back to space and cool the surface, while warming in the Eastern Pacific does not. This warming pattern is likely due to natural variability and may not persist in the future. 15/19
If the warming pattern in the Pacific changes to be more similar to that in climate models, Dessler and colleagues argue that it would result in between ~0.3 and ~0.6 w/m^2 additional radiative forcing (or 0.2C to 0.5C more warming, assuming 3C ECS). 16/19
So, in essence, Dessler and colleagues results would suggest that the world could warm 0.2C to 0.5C more under our best estimate of ECS even in a zero emissions scenario due to pattern effect changes. 17/19
However, not all of this warming would happen by 2100 (indeed, we really don't know when the Pacific warming pattern might shift!). The impact on meeting Paris Agreement goals would be smaller, though exactly how much depends on when the warming pattern changes. 18/19
I don't think this paper fundamentally changes our understanding of committed warming, and pattern effects are still an area of active research. But it should make us a bit cautious about being too confident in predictions of zero warming after emissions reach net-zero. 19/19

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The UK government's climate advisory body is launching its next carbon budget: basically, outlining what the UK can emit between 2033 and 2037. It's a big deal - launch video starting right now.
Watch along:


Will tweet along snippets. Pretty relevant to...............everything, really. #UKCarbonBudget

"Instead of being just a budget, it's a pathway we have to tread to reach net zero in 2050" @lorddeben

Just like quite a few other modelling exercises, CCC use a spectrum between behaviour change and between technological change. #UKCarbonBudget.

Both = best (just like @AEMO_Media's Step Change scenario in their ISP)


'Balanced' is what they use for their recs. "We're doing 60% of the emissions reductions in the first 15 years, and then 40% in the next".

The slinky kitty curve....good to see. No evidence of delaying action to Dec 29 2049, here. #UKCarbonBudget


"By front loading, we're minimising the UK's contribution to cumulative emissions" - really important point. A slow path to net zero - more climate harm than a fast one. #UKCarbonBudget

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Assalam Alaiki dear Sister in Islam. I hope this meets you well. Hope you are keeping safe in this pandemic. May Allah preserve you and your beloved family. I would like to address the misconception and misinterpretation in your thread. Please peruse the THREAD below.


1. First off, a disclaimer. Should you feel hurt by my words in the course of the thread, then forgive me. It’s from me and not from Islam. And I probably have to improve on my delivery. And I may not quote you verbatim, but the intended meaning would be there. Thank You!

2. Standing on Imam Shafii’s quote: “And I never debated anyone but that I did not mind whether Allah clarified the truth on my tongue or his tongue” or “I never once debated anyone hoping to win the debate; rather I always wished that the truth would come from his side.”

3. Okay, into the meat (my love for meat is showing. Lol) of the thread. Even though you didn’t mention the verse that permitted polygamy, everyone knows the verse you were talking about (Q4:3).


4. Your reasons for the revelation of the verse are strange. The first time I came across such. I had to quickly consult the books on the exegeses or tafsir of the Quran written by renowned specialists!
I like this heuristic, and have a few which are similar in intent to it:


Hiring efficiency:

How long does it take, measured from initial expression of interest through offer of employment signed, for a typical candidate cold inbounding to the company?

What is the *theoretical minimum* for *any* candidate?

How long does it take, as a developer newly hired at the company:

* To get a fully credentialed machine issued to you
* To get a fully functional development environment on that machine which could push code to production immediately
* To solo ship one material quanta of work

How long does it take, from first idea floated to "It's on the Internet", to create a piece of marketing collateral.

(For bonus points: break down by ambitiousness / form factor.)

How many people have to say yes to do something which is clearly worth doing which costs $5,000 / $15,000 / $250,000 and has never been done before.
Great article from @AsheSchow. I lived thru the 'Satanic Panic' of the 1980's/early 1990's asking myself "Has eveyrbody lost their GODDAMN MINDS?!"


The 3 big things that made the 1980's/early 1990's surreal for me.

1) Satanic Panic - satanism in the day cares ahhhh!

2) "Repressed memory" syndrome

3) Facilitated Communication [FC]

All 3 led to massive abuse.

"Therapists" -and I use the term to describe these quacks loosely - would hypnotize people & convince they they were 'reliving' past memories of Mom & Dad killing babies in Satanic rituals in the basement while they were growing up.

Other 'therapists' would badger kids until they invented stories about watching alligators eat babies dropped into a lake from a hot air balloon. Kids would deny anything happened for hours until the therapist 'broke through' and 'found' the 'truth'.

FC was a movement that started with the claim severely handicapped individuals were able to 'type' legible sentences & communicate if a 'helper' guided their hands over a keyboard.