These current policy or NDC projections have been a mainstay of the @UNEP Emissions Gap Report & @climateactiontr.
These approaches have been based on statistical matching with existing scenario databases.
We wanted to used models to extend 2030 policies & pledges to 2100.
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(noting that EGR now does a different approach more similar to our paper, other projects have extended current policies & NDCs such as in CD-LINKS & ADVANCE, the difference is we focus on the issue)
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But, how do you extrapolate policy effort from 2030 to 2100, & in a way that can cover the mechanics of a diverse set of models.
We came up with two approaches, extrapolating based on carbon price extensions & extrapolating based on emission intensity projections.
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Even though we harmonised many input data & assumptions across out models, there is a very large spread in temperature outcomes.
We used a diverse set of models, so focused on CO₂ emissions, had to extend some to 2100, & estimated temperature using simplified approaches.
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But why the spread in results?
Different models have different baseline 'no climate policy' emissions (red) & different response to climate policy (yellow), & these factors dominated the differences.
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We also took some effort to try & explain the results, here for final energy, but without dedicated & specific model-by-model analysis it is perhaps hard to isolate differences. We did not find any strong evidence of model type, structure, etc, pushing results either way.
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The first question on many lips is "how much CCS" (well, my first question).
We run each model with current policies, & a carbon price which gives the same emissions as the current policies, & found that the carbon price leads to much greater deployment of CCS.
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This indicates that the evolution of the energy system is very dependent on the types of policies implemented, notably whether a carbon price versus a regulation, standard, incentive, etc.
Most scenarios are based around carbon prices, & so high levels of CCS may follow...
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Have a look at the paper, there is much more detail than in this thread!
Many interesting aspects to explore. Up next, carbon-climate feedbacks? Maybe...
In case it was not clear, the 2.2-2.9°C range is the median temperature outcome across the models used. If we additionally include climate uncertainty via the TCRE, the range becomes 1.7-3.8°C.
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This question is ambiguous: "How high above pre-industrial levels do you think average global temperature will rise between now and 2100?"
* ...pre-industrial... between "now and 2100"?
* Where we are currently heading or where we could head? This is largely a policy question?
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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...
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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!
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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?
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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!