You may have heard that after revisions to land-use change emissions, total global CO₂ emissions are approximately flat over the last decade (black line).
But, how much do we revise carbon budget components each year?
Let's have a look...
1/
Fossil CO₂ emissions are revised each year, particularly the last decades. We update data & improve methods. Chinese data has had major revisions & cement was completely revised in 2018, plus lots of smaller improvements.
Land-use change (LUC) emissions are much more uncertain:
* 2014-2015: one bookkeeping model used
* 2016-2019: two bookkeeping models used
* 2020-2021: three bookkeeping models used
* 2021: major update of land-use forcing (change) datasets
Uncertainty remains high! Beware!
3/
The land sink (outside of areas considered LUC) is mainly due to CO₂ fertilization & climate effects:
* 2014-2016: estimated as a residual from the budget balance
* 2017-2021: estimated independently using models (leading to a budget imbalance, see below)
4/
The ocean estimates show more revisions as methods have changed:
* 2014-2016: models were scaled to match an estimate of the ocean sink in the 1990s
* 2017-2020: average of models
* 2021: average of models & data products (which have a greater sink
5/
A side note: From 2020 we have included a CO₂ sink from cement carbonation, where CO₂ is slowly taken up over time in concrete structures.
An open question is whether to aggregate the sink to fossil emissions or keep separated.
6/
The atmospheric CO₂ concentration is the best constrained & revisions are small & usually the final year.
The carbon budget should close due to mass balance:
Fossil + LUC = Sinks (land + ocean) + atmospheric increase.
But, we measure these all independently...
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Because we estimate each budget component independently, & the budget must close, we get a 'budget imbalance' (BIM), which is how far we were from closing the budget.
Our goal is to get this as close to zero as possible... We started doing this in 2017.
8/
This year there was a major revision in LUC (lower) & the ocean sink method was changed (bigger sink), compounding the BIM.
We now have a larger drift in the BIM in the last decade & now our task is to understand why...
One of the key arguments that Norway uses to continue oil & gas developments, is that under BAU it is expected that oil & gas production will decline in line with <2°C scenarios, even with continued investment.
Let's look closer at these projections & reality...
1/
Here is the projections from the 2003 report from the petroleum agency.
In reality (tweet 1) there was a dip around 2010, but production is now up around 250 million cubic again.
The forecast was totally & utterly WRONG!
2/
In 2011 there was a forecast for an increase in production to 2020, but then a decline. This is probably since they started to put the Johan Sverdrup field on the books.
The increase in production was way too low, again, they got it wrong.
CO2 emissions by fossil fuel:
* We thought coal peaked in 2014. No, & up another 1.1% in 2023
* Oil up 1.5%, on the back of a 28% increase in international aviation & China, but oil remains below 2019 level. 🤞
* Has the golden age of gas come to an end thanks to Russia?
2/
By top emitters:
* China up 4.0% & a peak this year would be a surprise
*US down 3.0%, with coal at 1903 levels
* India up 8.2%, with fossil CO2 clearly above the EU27
* EU27, down 7.4% with drops in all fuels
* Bunkers, up 11.9% due to exploding international aviation
Is the new @DrJamesEHansen et al article an outlier, or rather mainstream?
At least in terms of the key headline numbers, it seems rather mainstream, particularly if you remember most headline key numbers have quite some uncertainty!
The Remaining Carbon Budget for 1.5°C is now smaller because: 1) We have not reduced emissions in three years 2) Updated simple climate models because of updated historical aerosol emissions 3) Some new method choices
The update for 2°C has similar changes for each component, but because the budget is much bigger, the changes don't seem that dramatic. Not Nature Climate Change worthy...
The changes to the 1.5°C budget seem dramatic, because the budget is basically gone.
2/
These updates are not new. A few years back 1.5°C was considered "geophysically impossible", but not after a revised budget:
I wrote a post on the utility of 1.5°C budgets back then, obviously ignored. Also on non-CO2.