If global CO₂ emissions stay at net zero, either:
* All countries need to be net zero ~2050, or
* Rich countries have net negative emissions post-2050, allowing developing countries to emit longer post-2050.
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If the world exceeds the 1.5°C carbon budget, then global net negative CO₂ emissions are required to return back to 1.5°C.
In this case, the net negative emissions reverse previous warming rather than allowing fairness (though, both are possible).
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Our scenarios are illustrative & selected to highlight choices, but they clearly show the flexibility for developing countries if the OECD and China get to net zero earlier and ultimately maintain net negative emissions.
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There are risks, obviously.
Developed countries have delayed adequate climate action for the past two decades, there is a real prospect of net-negative emissions turning into a never-ending promise of paying back initial “carbon debt” sometime later.
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Developing countries must therefore be wary of moving from demanding immediate and steep emission reductions to shifting attention toward Carbon Dioxide Removal (CDR).
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The demand for net negative emissions from developed countries needs to be stated.
If a developing countries pledges net-zero emissions post-2050, then to be consistent with 1.5°C it may have to depend on net negative emissions from developed countries, even if not stated.
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There has been increasing attention on the need for CDR, either as a way to balance residual emissions or to undo previous warming.
There has been much less discussion on CDR as a way to facilitate fairness.
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There have been hefty critiques of net zero in the past year, but maybe a shift from net zero to net negative and fairness shifts the focus?
"Instead of leaving such work to volunteers, global institutions should marshal the funding & expertise to collect crucial data, & mandate their publication"
💯agree with @_HannahRitchie. No one wants to fund the giant who's shoulders we stand on.
The approach to science is to fund big models, expensive observations, etc. All this is needed, but somehow science seems to have forgotten the importance careful curation & maintenance of data.
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Science is full of projects that improve models, do model comparisons, process some satellite data, etc, & if you are lucky there might be a task that scrapes together some data to feed the models.
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Scientific studies (eg IPCC Assessment Reports) generally consider CO₂ emissions from 'Net Conversions' as the emissions, while government reporting to the UNFCCC combines the conversions & sink (black line).
The 'sink' is not the total sink, only a part of the forest sink.