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Oliver Geden Profile picture
@Oliver_Geden
Dec 4, 2018 • 4 tweets • 4 min read • Read on X
#UNEP Emissions Gap Report 2018 shows (once again) that current (unconditional) NDCs under the Paris Agreeement would not eben lead to a global emissions peak before 2030
(2017: 53 Gt CO2eq -> 2030: 56 Gt CO2eq)
unenvironment.org/resources/emis…
#COP24 Image
Full implementation of (unconditional) NDCs would lead to temperature increase of 2.9-3.4 °C by 2100, albeit based on rather opaque 'constant level of effort throughout century' methodology (see agupubs.onlinelibrary.wiley.com/doi/full/10.10…)
unenvironment.org/resources/emis…
#COP24 Image
It was already clear at #COP21 in Paris that 1st round of national pledges wouldn't get us near 1.5-2 °C. That's why 'ratcheting-up' was a fashionable term back then (e.g., carbonbrief.org/timeline-the-p…)
The term 'rachet' is still in use, but you hear it less often nowadays
#COP24 Image
Around #COP21 'ratcheting-up' was publicly treated like a legal obligation. But more & more scholars say that there isn't really one (e.g., tandfonline.com/doi/full/10.10…).
Which leaves the 'global stocktake'.
But, as Rajamani/Werksman note, it only takes stock
rsta.royalsocietypublishing.org/content/376/21… Image

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More from @Oliver_Geden

Oliver Geden Profile picture
Mar 31, 2023
As promised, now more on the topics I was deeply involved in as #IPCC #AR6 Synthesis Report author, both in the Summary for Policymakers & the so-called 'Longer Report':
overhoot, net zero, mitigation pathways (incl. CDR)

1/n
Let's start with "Overshoot" (B.7), where I was responsible for drafting and 'negotiating' in plenary, but of course not alone (mainly together with @chrisd_jones, with whom I worked on corresponding section 3.3.4 in underlying report)
#IPCC #AR6 #SYR
ipcc.ch/report/ar6/syr/
2/n
To understand the Overshoot SPM section B.7, we need to start with B.1 on "Future Climate Change", led by @JuneYiLee1 & @sorensson_anna
#IPCC #AR6 #SYR
ipcc.ch/report/ar6/syr/
3/n
Read 15 tweets
Oliver Geden Profile picture
Mar 20, 2023
Unfortunately, the UN Secretary General still doesn't understand difference betw net-zero CO2 and much more ambitious net-zero GHG targets. The famous 2050 is net-zero CO2 for 1.5C, net-zero GHG only some decades later, as per #IPCC WG3 & Synthesis Report
politico.eu/article/climat…
UN Secretary General has been ill-advised by his own high-level expert group on net-zero, which also confuses net-zero CO2 and net-zero GHG.
It is all in the latest #IPCC reports, including the one released today. Why not just "listen to the science"?
Read 4 tweets
Oliver Geden Profile picture
Mar 20, 2023
After 3 yrs of hard work & a long approval plenary, we got the #IPCC #AR6 Synthesis Report published today, consisting of the Summary for Policymakers and a full report version ➡️ ipcc.ch/report/ar6/syr/
An ongoing 🧵, starting with SPM fig 1 on adverse climate change impacts
1/n
Every increment of warming matters (SPM.2)
#IPCC #AR6 #SYR
ipcc.ch/report/ar6/syr/
[2/n]
Future climate change to increase impacts and regional differences
#IPCC #AR6 #SYR
ipcc.ch/report/ar6/syr/
[3/n]
Read 16 tweets
Oliver Geden Profile picture
Jan 19, 2023
Today we publish the 1st edition of the "State of Carbon Dioxide Removal" report, a global assessment of the current #StateofCDR, and the gap we need to close to achieve the Paris temperature goal.
Full report➡️stateofcdr.org
An ongoing 🧵
[1]
This report compiles a first estimate of the total CDR being deployed (2 GtCO2/yr).
Almost all comes from "conventional" CDR on land, via afforestation, reforestation & forest management.
"Novel" methods don’t contribute much yet.
#StateofCDR
[2]
We provide a calculation of total gross CDR in #IPCC-assessed pathways to keep warming below 1.5C and 2C, including all methods. All pathways involve substantial cumulative CDR volumes (450-1100 GtCO2 by 2100) - in addition to immediate & deep emissions reductions
#StateofCDR
[3]
Read 35 tweets
Oliver Geden Profile picture
Nov 8, 2022
The @UN #HLEGReport on Net-zero Emissions Committments is out
The problem though: #IPCC 1.5C pathways don't reach net zero GHG emissions by "2050 or sooner", but by the end of the century. The famous "net zero by 2050" (better "early 2050s) is CO2 only
un.org/en/climatechan…
1/
You might be in disbelief, but have a look at the #IPCC AR6 WG3 Summary for Policymakers, Table SPM.2:
For 1.5C with no or limited overshoot (category C1), pathways reach net-zero CO2 in 2050-2055, but net-zero GHG in 2095-2100
ipcc.ch/report/ar6/wg3…
2/n
The difference between net-zero CO2 and net-zero GHG can be explained by the dominant role of non-CO2 GHGs (methane, nitrous oxide, f-gases) in residual emissions and the dominant role of CO2 in removals
Read 14 tweets
Oliver Geden Profile picture
Apr 11, 2022
➡️Only 6 out of 97 scenarios in the #IPCC #AR6 WG3 category C1 ('no to limited overshoot') never cross 1.5C
➡️91 out of 97 cross 1.5C temporarily, and then go back to 1.5°C by 2100

If you read the Summary for Policymakers of IPCC AR6 WG1 (Aug. 2021), this cannot come as surprise
Below the numbers from #IPCC #AR6 WG1. Not sure if this knowledge was conciously included in "keeping 1.5C alive and within reach" messaging around #COP26.
'Overshoot' pathways (= exceedance & return) didn't make it onto the high-level #UNFCCC agenda yet
ipcc.ch/report/ar6/wg1…
The overshoot logic might also a little bit hard to detect in this #IPCC #AR6 WG1 SPM figure. That's because overshoot is quite small (0.1°C) for SSP1-1.9, while at the same time all standard RCP levels (1.9-8.5) are shown in one figure
ipcc.ch/report/ar6/wg1…
Read 6 tweets

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