When we wrote our @NatureClimate commentary ( http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... we thought readers would& #39;ve many examples of failed #climate deadlines on their minds, and decided to skip that part.
But obviously, there& #39;s need for a SUB-THREAD ON EVIDENCE FOR FAILED CLIMATE DEADLINES [r1a)
While many older colleagues seem to like the piece ( http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... many of the younger discussants didn& #39;t seem to know to which pre- #IPCC #SR15 experience we draw upon. Others, irrespective of age, simply might not want to deal with uncomfortable knowledge [r1b]
Although there are many earlier examples, let& #39;s start with the & #39;100 months& #39; campaign that began in 2008, obvs. ended in 2016 and led Mike Hulme to write his first piece on & #39;deadline-ism& #39; https://mikehulme.org/deadline-ism-when-is-it-too-late/">https://mikehulme.org/deadline-... ( http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [1a]
“Deadline-ism”: when is it too late?

Last Thursday was the first day of December 2016.  There was nothing particularly remarkable about the date.  Except that it was exactly 100 months since Andrew Simms and the New Economics Foundati…

https://mikehulme.org/deadline-ism-when-is-it-too-late/
Looking at @AndrewSimms_uk call for action https://www.theguardian.com/environment/2008/aug/01/climatechange.carbonemissionsended">https://www.theguardian.com/environme... you can imagine this being written in 2018 (just change 2C into 1.5C): "the IPCC says so", "time is running out". Well, time ran out (in 2016), but deadlines are still in fashion http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [1b]
You can of course say that "100 months" was just a political campaign. But there& #39;s also a history of scientists setting #climate deadlines. Like the "St James Palace Memorandum" of Nobel Laureates in 2009, just before COP15. http://www.newscientist.com/wp-content/uploads/2009/05/sjp_memorandum.pdf
(https://www.newscientist.com/wp-conten... href=" http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [2a]
The "St James Palace Memorandum" explicity says that 2C "can only be achieved" by a global peak of GHG emissions by 2015. Yet, it did not happen. But signatories chose not to stick to their deadline afterwards.
http://www.newscientist.com/wp-content/uploads/2009/05/sjp_memorandum.pdf
(https://www.newscientist.com/wp-conten... href=" http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [2b]
Instead, some of the high-level signatories of the 2009 declaration came up with a new deadline in 2017 - now GHG emissions are said to need to peak by 2020. We have "Three years to safeguard our climate"
https://www.nature.com/news/three-years-to-safeguard-our-climate-1.22201
(https://www.nature.com/news/thre... href=" http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [3a]
Three years to safeguard our climate

Christiana Figueres and colleagues set out a six-point plan for turning the tide of the world’s carbon dioxide by 2020.

https://www.nature.com/news/three-years-to-safeguard-our-climate-1.22201
In a Twitter conversation about that article, co-author @rahmstorf promised he would personally call off the 2C target if emissions don& #39;t peak by 2020 https://twitter.com/rahmstorf/status/880419849293504513">https://twitter.com/rahmstorf... He later deleted that tweet
( http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [3b]
But the figure from said @Nature article indicates several options how to extend that deadline again, first and foremost the size of the remaining carbon budget and the option to include net negative emissions
( http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [3c]
Before I continue: my apologies to @rahmstorf, he didn& #39;t delete the tweet, I didn& #39;t find it in my overcrowded deadlines folder https://twitter.com/rahmstorf/status/880417640635920385
That& #39;s">https://twitter.com/rahmstorf... all I expect: if you set a deadline stick to it and say "game over" when deadline is missed ( http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [3d]
When I was younger, I expected scientists to stick to these kind of deadlines. That& #39;s what led me to say already in 2011 that 2C isn& #39;t feasible (which didn& #39;t make me a lot of friends, obvs.) ( http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [r2a]
Then one day a modeller told me w/ a smile that they& #39;ll never call 2C off (no 1.5C scenarios back then), they& #39;d just push more negative emissions into scenarios. It was meant as a joke, obvs., but it got me interested into deadline flexibilities ( http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [r2b]
I found that there are many flexibilities that enable a constant shift of deadlines, modifying the meaning of 2C (or 1.5C), including lowering probabilities, allowing temporary overshoot, allowing more carbon removal.
https://www.swp-berlin.org/en/publication/climate-modifying-the-2-c-target/
(https://www.swp-berlin.org/en/public... href=" http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [r2c]
Modifying the 2°C Target

Climate Policy Objectives in the Contested Terrain of Scientific Policy Advice, Political Preferences, and Rising Emissions

https://www.swp-berlin.org/en/publication/climate-modifying-the-2-c-target/
All these modification options are not only threatening the integrity of climate policy, but also of scientific advice to climate policy (and eventually #climate research itself)
( http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [r2d]
Here are some articles I wrote about deadline modifications (stemming of course from political inaction, but at the same time masking inaction)
https://www.nature.com/news/policy-climate-advisers-must-maintain-integrity-1.17468
https://www.nature.com/news/poli... href=" https://onlinelibrary.wiley.com/doi/full/10.1002/wcc.427
https://onlinelibrary.wiley.com/doi/full/... href=" https://www.nature.com/articles/s41561-017-0026-z
https://www.nature.com/articles/... href=" https://rdcu.be/0TiG 
(https://rdcu.be/0TiG"... href=" http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [r2e]
Define limits for temperature overshoot targets

Temperature overshoot scenarios that make the 1.5 °C climate target feasible could turn into sources of political flexibility. Climate scientists must provide clear constraints on overshoot magnitu...

https://www.nature.com/news/policy-climate-advisers-must-maintain-integrity-1.17468
But back to examples. Consider the annual UNEP Emissions Gap Report, analysing the pledges made in Copenhagen and compare the aggregate estimate with a 2C-compatible level (in 2020/2025/2030).
( http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [4a]
When UNEP started this effort in 2010 the Gap was already huge https://www.unenvironment.org/resources/emissions-gap-report-2010,">https://www.unenvironment.org/resources... and because of insufficient action, it grew over time, with the prospect that the Gap could never be closed by 2020.
( http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [4b]
The Emissions Gap Report 2010

Climate change represents one of the greatest challenges but also an inordinate opportunity to catalyse a transition to a low carbon, resource-efficient Green Economy. This report informs Governments...

https://www.unenvironment.org/resources/emissions-gap-report-2010
While emissions kept rising, UNEP moved the goalposts, increasing emissions benchmark values, by introducing a new scenario category.
https://rdcu.be/0TiG 
(https://rdcu.be/0TiG"... href=" http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [4c]
From a modelling perspective, such a change in methodology is perfectly fine, but used at the science/policy interface it leads to the impression among policymakers that it will always be five finutes to midnight
https://rdcu.be/0TiG 
(https://rdcu.be/0TiG"... href=" http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [4d]
Before I go on a brief vacation, some words on the 1.5C targets and remaining carbon budgets. Many activists & policymakers treat budgets as if we deal with a calculation/methodology that never changes, e.g. @FridayForFuture https://twitter.com/FridayForFuture/status/1144527222553960448
(https://twitter.com/FridayFor... href=" http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [5a]
But in fact they change all the time (scientific progress is of course part of that story), but there are many different methodologies even today, as highlighted in this recent @Nature paper by Rogelj et al. http://rdcu.be/bKIWi 
(https://rdcu.be/bKIWi&quo... href=" http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [5b]
Looking at remaining budget numbers today (420 Gt for 66% from 2018), these are the product of a changed methodology in #IPCC #SR15 that led to an extension of the budget by ~300Gt. Some scientists found that questionable, NGOs and activists didn& #39;t
( http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [5c]
Without that change in methodology (which I& #39;m not an expert on - see maybe @Peters_Glen& #39;s blog https://cicero.oslo.no/no/posts/klima/beyond-carbon-budgets)">https://cicero.oslo.no/no/posts/... the 1.5C budget would almost be gone (below a figure with the old numbers. Of course, policymakers found that convenient
( http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [5d]
This move & #39;forced& #39; (and I mean & #39;forced& #39;, because they didn& #39;t like it) organisations like @MCC_Berlin to reset their carbon clocks https://www.mcc-berlin.net/en/research/co2-budget.html">https://www.mcc-berlin.net/en/resear... Of course they describe the methodology, but does the public (or activists) notice?
( http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [5e]
As a side effect, the budget for 2C also grew substantially. According to #SR15, the new net zero GHG year for 2C is now beyond 2100. And the new net zero GHG year for 1.5C is 2067 (not 2050, as often reported, that& #39;s CO2 only).
( http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [5f]
So, budget calculations do change, there& #39;s no "we only have 12 years left", and theoretically, it could also go the other way again. So maybe better focus on a target that isn& #39;t moving all the time: net zero (GHG) emissions https://kleinmanenergy.upenn.edu/policy-digests/targeting-net-zero-emissions
(https://kleinmanenergy.upenn.edu/policy-di... href=" http://rdcu.be/bLiok )">https://rdcu.be/bLiok&quo... [5g]
Targeting Net Zero Emissions

Temperature targets have advanced the climate policy debate, but failed to catalyze appropriate action—net zero emissions targets can deliver on both ends.

https://kleinmanenergy.upenn.edu/policy-digests/targeting-net-zero-emissions
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