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Glen Peters

@Peters_Glen

7 Oct

There is often an assumption that the more aggressive climate targets means more BECCS.

This is only weakly true, many 2°C scenarios use as much BECCS as 1.5°C scenarios, & even >2.5°C scenarios use BECCS at scale!

IAMs just love BECCS 😍🥰😘

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These are scenarios that go over 2°C. Yes, some scenarios use over 20GtCO₂/yr in 2100 (we currently emit 40GtCO₂/yr). These are not aggressive mitigation scenarios, these are >2°C, & where we could end up with only weak climate policies like we have today.

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It is not that 1.5°C or 2°C (or even 3°C) needs large-scale BECCS, this is just the cost-effective pathway that most IAMs find. This could be for a variety of structural reasons.

Since BECCS is so prolific in scenarios, we obsess over it. It may just be a model artifact!

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Glen Peters

@Peters_Glen

6 Oct

The results of yesterdays poll on EU climate ambition.

There was some ambiguity with the question, essentially to what degree the EU should adjust to the ambition of others.

There was a reason for the way I posed the question, around net-zero, linking to the ">2°C" option

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Scenarios with 50% chance of staying below 2°C rarely reach net-zero GHG by the end of the century (from IPCC SR15). The EU is aiming for net-zero GHG in 2050. The EU, in this case, would be more than 50 years ahead of the global average.

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This is the temperature response from those scenarios, still below 2°C (median in 2100 is 1.8°C).

So, to pick the option that the EU is consistent with over 2°C (>2°C in the poll) is rather extreme, & I would say inconsistent with the science (sorry).

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Glen Peters

@Peters_Glen

5 Oct

How is a 1.5°C scenario defined?

It should be simple to define? No? These are the definitions used in IPCC SR15, which has three types of 1.5°C scenarios depending on "overshoot".

This has implications...

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The Paris agreement has "well below 2°C ... pursing ... 1.5°C". A broad interpretation would be somewhere between 1.5°C-2°C (closer to 1.5°C).

This is where the SR15 scenarios go. The 1.5°C scenarios are generally below 1.5°C except for a period of over 1.5°C.

And so?

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This 'overshoot' has big implications for Carbon Dioxide Removal (CDR). Here is CDR just from BECCS... Add on top of this CDR from afforestation!

Choosing aggressive definitions of 1.5°C generally requires assuming more CDR. Which is fine, as long as this trade-off is clear.

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Glen Peters

@Peters_Glen

25 Sep

"We estimate that 30 years of natural forest regrowth across 349 Mha & 678 Mha could [lead to uptake of 5.9 to 8.9 GtCO₂/yr]". This includes some below ground carbon.

Plenty to unpack, but how does it compare to emission scenarios?

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nature.com/articles/s4158…

1.5°C scenarios with no or low overshoot from #SR15 have afforestation in 2050 (30 years from now) consistent with those numbers (some even higher).

Worth noting, the CO₂ uptake will not continue at that high rate...

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IAMs that provide data on land use for afforestation use similar areas, of ~350-650Mha in 2050.

The carbon uptake rates seem broadly in the same ranges (though harder to check given the data reported in IAMs).

At least, no glaring inconsistencies...

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Glen Peters

@Peters_Glen

24 Sep

https://twitter.com/Peters_Glen/status/1308690343802613761

Come on Tweeps, surely afforestation is a Negative Emission Technology (NET)?

This pole really surprised me, 50% think afforestation is not a NET. Wow. I mean WOW. When did this happen?

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https://twitter.com/Peters_Glen/status/1308690343802613761

Many said they use process, or mechanism, or similar, & prefer Carbon Dioxide Removal (CDR). This is really coming down to what is a "technology".

Others basically said it is a question of efficacy. Does it work? If not, it is not a NET. I didn't think of that issue.

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I could go through numerous articles where afforestation is a NET. IPCC says afforestation is a NET depending on report, more commonly CDR.

Here is one article, just as an example
iopscience.iop.org/article/10.108…

CDR is a much better term, but afforestation is still a NET... (IMHO)

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Read 8 tweets

Glen Peters

@Peters_Glen

24 Sep

@IvoHlebarov

@IvoHlebarov @PeterGleick @MichaelEMann @JKSteinberger @KHayhoe It is what the IPCC says. The way framed in the thread is not quite correct. Yes, the 50% and net zero 2050 is based on scenarios with carbon dioxide removal. You can do stylised with a carbon budget, and take the numbers from SR15 Table 2.2.
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@IvoHlebarov

@IvoHlebarov @PeterGleick @MichaelEMann @JKSteinberger @KHayhoe If we just accept these numbers (& not quibble over temp baselines, feedbacks, etc). These budgets are defined on when emissions reach zero (and temperature is about peak). The IPCC statement is equivalent to 50% 1.5C (at peak).

Area of triangle: 580*2/42=28 years to zero

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@IvoHlebarov

@IvoHlebarov @PeterGleick @MichaelEMann @JKSteinberger @KHayhoe Lets say that budget says zero globally in 2045, with absolutely no CO2 removal. If that is the criteria you want, then all countries can emit zero after 2045.

You want 66%, the 420GtCO2 budget? There are no scenarios in the literature, that I know of, that can do that!

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