We currently emit 40GtCO₂ (net) & scenarios remove ~10GtCO₂ (net). We are unlikely to be in a symmetric situation with emissions & removals. 40GtCO₂ net removal unlikely & also displaced in time.
We may have bigger gross emissions, but the atmosphere sees net emissions.
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How to interpret such big pulses?
These experiments are 100-500GtC (366-1800GtCO₂), which we may emit over 10-50 years.
I see these experiments as more like the long-term response (say >50 years).
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Based on this, I would treat emissions & removals as the same from an atmospheric perspective (with appropriate waivers).
But there are big differences in an emission sense (measurement & permanence of removals are difficult to ensure).
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PS. We still need to do these idealised experiments, to confirm the size of the asymmetry...
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One of the reasons is that emissions are given as zero in the energy sector (reported as a memo), which means it is necessary to model the land sector to analyse bioenergy (or material substitution).
Increasing forest harvest, e.g. to increase bioenergy or material substitution, all else equal, means a smaller land sink. But, a land sink is needed to help reach net zero (may not be possible to get all emissions to exactly zero).
3. The forest sink is mainly from forests remaining forests, so carbon uptake comes from management or environmental factors (CO₂ fertilisation, climate change).
Afforestation can be increased & emissions from other land use types & transitions can be decreased.
Based on the new NGFS scenarios, up to a 60% drop in fossil CO₂ emissions by 2030. This includes a pathways with divergent polices (Divergent Net Zero).
(Different colours, different IAM).
EU & US reach net zero around 2040-2060, depending on model and scenario.
For the lingo, "Net Zero 2050" is an orderly transition to 1.5°C & "Divergent Net Zero" is a disorderly transition to 1.5°C, implying policies are implemented immediately, but not uniformly.
Don't ask about India...
[Technically, I guess the rebound in MESSAGE is since carbon prices stop growing (& decline) after net zero, which allows India to emit more. That would be my hypothesis... Is this rebound believable?]
There is no physical transfer of electricity, just a digital transaction with some $.
A GoO is basically a certificate to say that some renewable electricity was produced, & the certificate is then sold onward to an entity. The entity then claims they are using renewable electricity, even if they are connected only to a coal power plant.
The average consumer that is physically using the renewable electricity generally has no idea about this virtual transaction. So, Norwegian's think they are using Norwegian hydropower & German's think they are using Norwegian hydropower. I guess no one is using the coal then?
The EU has a LULUCF sink of ~250MtCO₂/yr:
* ~300MtCO₂/yr is forests remaining forests (a share of which is due to climate change & CO₂ fertilisation)
* ~50MtCO₂/yr is land converted to forests
* ~50MtCO₂/yr is increased storage in wood products
* The rest is a source
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This sink has a huge policy significance, as the sink allows to offset emissions in hard-to-mitigate sectors & reach net zero in 2050.
But, using forests could also help reach net-zero by displacing some fossil fuels?
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Just focusing on forests, the EU could increase harvest, weakening the sink, & use the harvest to displace materials (e.g. cement in construction) or fossil fuels (e.g., bioenergy).
But here lies the problem. The tendency is then to make models more complex. This does not solve the problem. Models are so complex barely anyone can understand what drives what.
Reform is needed so "researchers can examine the trade-offs between making models tractable & making them more useful for real-world decisions"
To me, this means you need different types of models, different types of tools & approaches, not bigger models.
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Overwhelmingly, it seems most research funding is aimed at building more complex models. And nearly all funding is tied up by the big modelling groups.
Imagine an ERC or EU project, "here is my simple toy model". Laughed out of the room, but this is what is needed.
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Increasingly scenario users are interested in 'where we are heading' as a baseline, rather than no climate policy scenarios (light grey) & SSP5-85 (RCP85).
Current policies may take the world to ~3.2°C (10-90% range 2.3-4.4°C due to climate uncertainties), which is much less than >5°C in SSP5-85.
The bold lines are from the NGFS scenarios used by financial institutions for 'stress testing', the thin lines are from IPCC SR15.
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Another organisation that has been doing work on 'where we are heading' is the @climateactiontr, which has quite consistent numbers as the NGFS (though quite different methods).
* NGFS is based on modelling
* CAT is more a statistical approach