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Glen Peters Aug 22
Replying to @Peters_Glen
8. “RCP8.5 is, because of its assumptions of high population & slow technological progress, on the higher end of the range of possible baseline scenarios…I wished I would have been clearer with what I meant by business as usual in that paragraph.”
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Glen Peters Aug 22
Replying to @Peters_Glen
9. The new Shared Socioeconomic Pathway (SSP) framework is more explicit that there are a range of baselines (grey region), depending on socioeconomics (& IAM). Some baselines have declining emissions...
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Glen Peters Aug 22
Replying to @Peters_Glen
10. The energy system of each baseline is very different across SSPs, but also across IAM. In my view, the variation across IAM should receive as much attention as variation across SSPs...
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Glen Peters Aug 22
Replying to @jritch
11. Some baselines have pretty crazy coal use, something & others have argued is based on bad modelling assumptions. Today, even without climate policy, it is likely solar & wind will out-compete coal in the future.
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Glen Peters Aug 22
Replying to @Peters_Glen
12. A fundamental issue, in my view, is that there is no longer a no policy world. We have climate policy, albeit weak, and that should be embedded in the baseline. (Weak) climate policy may have already avoided ~1°C of future warming...
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Glen Peters Aug 22
Replying to @Peters_Glen
13. For balance, climate modellers like RCP8.5 for continuity with previous modelling, signal-to-noise, illustrate potential avoided impacts, potentially capturing unrepresented feedbacks, etc. Sure, but eventually you have to let go of the past...
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Glen Peters Aug 22
Replying to @Peters_Glen
14. There is also a view that we are following high-end pathways. I wrote a paper on it (whoops) . Though, things have changed somewhat in the last 5 years...
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Glen Peters Aug 22
Replying to @Peters_Glen
15. Scenarios are often reported with 10 year time steps, scenarios are updated regularly, & in a sense, we are always on track... This figure shows the latest SSPs (with the CMIP6 markers in bold)
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Glen Peters Aug 22
Replying to @Peters_Glen
16. It is best to look at progress relative to the underlying energy system. This figure comparing across AR5 scenarios...
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Glen Peters Aug 22
Replying to @Peters_Glen
17. Why is this all a problem? In my view, if you push up baselines, imply lack of progress, then it makes 1.5°C or 2°C look harder. We should truly reflect how we are going, & how easy some gains are (even if 1.5°C or 2°C is out of reach)
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Glen Peters
18. A key challenge is that it takes decades for climate signals to emerge if two scenarios are close (bottom), even though, the mitigation pathways can be dramatically different (top). Maybe that means we will forever have tensions between mitigation & impact research? /END
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Paul Pukite Aug 22
Replying to @Peters_Glen
Explainer: Our book Mathematical Geoenergy on energy and climate analysis combines powerful FF modeling techniques with applied physics derivations of both man-made and natural (i.e. ENSO) climate variations.
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Rust Never Sleeps / George Morrison 🇨🇦 Aug 24
Thanks for highlighting this sub-tweet, This is in so many ways the essence of our policy dilemma/inertia. And "12 years or bust!"-messengers should study these plots *very* carefully. , you may find these two panels keepers.
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Shane Austin Aug 22
unroll please
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