Discover and read the best of Twitter Threads about #SR15

Most recents (24)

#OnThisDay, one year ago, the @IPCC_CH published its Special Report on the #ParisAgreement 1.5ºC temperature target, which has transformed scientific, political and societal discourse on #ClimateChange
Today we're reflecting, courtesy of some graphics from our very own @johnlangab, what the #SR15 report told us about the reduced impacts and reduced risks of keeping global warming to 1.5ºC rather than 2ºC
First up, a reduction in very hot years. Which of course means fewer people exposed to health risks of extreme heat
Read 12 tweets
Thread: Blatant #ClimateDenial has lost. The new conflict is whether #ClimateChange is a crisis requiring urgent social and #economic transformation, or something we can adapt to incrementally while carrying on with business as usual. 1/40
2/ A recent opinion piece by Bjorn Lomborg in the @globeandmail is representative of the 'business as usual argument'. Let's deconstruct it to see how this gets passed off as the pragmatic point of view, and why it's false.…
3/ The basic tactic is this: provide a few common-sense truths to gain the air of pragmatism and then feed us the story we're desperate to hear: that everything will be fine, that growth will outpace #ClimateDamages and life can carry on as usual.
Read 41 tweets
India has pledged to reduce its emission intensity by 33-35% from 2005 levels by 2030. Given the growth in GDP, this means emissions will rise ~5% per year to 2030.

According to #IPCC #SR15, global CO₂ needs to go down 45% from 2010 levels by 2030.

According to the Climate Action Tracker @climateactiontr India's pledge is compatible with 2°C. This is because India has low per capita and historical responsibility.

But, the less India does, the more other countries have to do (CO₂ is cumulative)…

The US, who has a completely inadequate pledge, would be compatible with 2°C if emissions were cut >50% by 2020-2030.

For India to be compatible with 2°C, the US has to do the impossible!

Read 4 tweets
This has not changed from earlier #IPCC assessments (like #AR5 or #SR15), but, not surprisingly, trade-offs with other forms of land-use are better highlighted in #SRCCL
All mitigation pathway archetypes for 1.5-2 °C (RCP1.9/2.6) include large volumes of carbon dioxide removal, even the very optimistic Pathway 6 that excludes engineered CDR (represented by BECCS) but relies on a large land sink… (ch 2.6.2) #SRCCL
Cumulative CDR volumes by 2100 for these 6 archetype mitigation pathways are quite high
P1: 395 Gt BECCS + 73 Gt Afforestation
P2: 466 Gt BECCS + 117 Gt AF
P3: 944 Gt BECCS only
P4: 300 Gt BECCS + 428 Gt AF
P5: 252 Gt BECCS + 128 Gt AF
P6: 124 Gt AF only
Read 5 tweets
Last Monday, I was invited to speak on the occasion of the 100 years anniversary of the International Union of Geodesy and Geophysics @theIUGG @UNESCO.
@theIUGG @UNESCO It was an opportunity to reflect on a success story, a failure story, and a transformation story, looking both backwards and forward.
@theIUGG @UNESCO Looking backwards, it is extremely impressive to consider the climate science achievements of the past century.
Read 78 tweets
Es hat mich gefreut, die Ergebnisse des @IPCC_CH #SR15 Berichts an @spzuerich Delegiertenversammlung vorzustellen. Netto-Null CO2 müssen wir so schnell wie möglich erreichen, spätestens in 2040-2050. Einige Länder haben bereits Gesetze dazu verabschiedet. @seilergraf @hosjon00
S. auch dazu kürzlich erschienenen #GAIA Artikel von @sciforfuture. @wozukunft @Knutti_ETH…
Read 3 tweets
Une journaliste m'interpelle aujourd'hui, je cite : "comment répondre à un climatosceptique influent qui me dit à l'instant, qu'il n'y a pas de scientifique au GIEC" 😯 (1/...)
Bon, alors première chose : le GIEC a pour mission d'évaluer les informations scientifiques, techniques et socio-économiques pour comprendre le fonctionnement du climat, les risques liés au réchauffement climatique, et les options d'action (adaptation, atténuation) (2/...)
Le GIEC ( ne fait pas de recherche, mais évalue l'état des connaissance sur la base des publications scientifiques, de manière rigoureuse, objective et transparente. (3/...)
Read 11 tweets
Message to fellow climate scientists & #ClimateTwitter: After seeing many variations on theme "Are we going to reach a catastrophe in 12 years?”, I think it could be more helpful if we were focusing instead on: "How much climate change can still be considered safe?” (Thread; 1/n)
This thread builds upon my recent @theAGU webinar (see below) and the @IPCC_CH #SR15 report… (2/n)
Many scientists point - rightfully - to the fact that we cannot state with certainty that climate would suddenly go berserk in 12 years if we weren’t doing any climate mitigation. But who can state with certainty that we would be safe beyond that stage or even before that? (3/n)
Read 23 tweets
Nach Lektüre des Klimapapiers der @FDP_Liberalen…: Will niemandem unterstellen. Aber ein paar Missverständnisse gibt es zu klären (1/12):
Z. 3-4: Klima und Artenschwund "eine bedeutende Herausforderung": wenn man @IPCC_CH #SR15 oder @IPBES #GlobalAssessment gelesen hat, kann man das nur als verharmlosend bezeichnen. (2/12)
Z 35: THG-Emissionen müssen "bis zweite Jahrhunderthälfte auf netto null". Seit @IPCC_CH #SR15 wissen wir: um Ziele des #ParisAgreement zu erreichen spätestens 2050, und reiche Länder müssen nach PA wie nach UNFCCC vorangehen. (3/12)
Read 12 tweets
Is CO₂ removal (negative emissions) needed in 1.5°C scenarios?

Highly likely. There are two 1.5°C scenarios with no or limited overshoot in #SR15 that do not have CO₂ removal (from the POLES) model, all others use afforestation, BECCS, DAC, etc
And here are the CO₂ emissions for the 1.5°C scenarios with no or limited overshoot. The black lines are the 4 Illustrative Scenarios used in the SPM. The red are the two POLES scenarios without CO₂ removal.
A reasonable question is how much of the CO₂ removal is afforestation?

Initially, almost all CO₂ removal is afforestation, but that share gets smaller over time as BECCS (in particular) grows. A few scenarios only use afforestation (from LED & C-ROADS).
Read 3 tweets
THREAD on IEA, IPCC, & 1.5°C scenarios

The @IEA is getting pressure to do a 1.5°C scenario. We have an #IPCC Special Report on 1.5°C #SR15, so why not do a comparison...

As it happens, some IEA scenarios fall in the envelope of 1.5°C scenarios...

What are the IEA scenarios?
* Energy Technology Perspectives 2°C scenario (2DS, not in #SR15 database)
* ETP Beyond 2°C Scenario (B2DS, in database)
* IEA Sustainable Development Scenario (SDS, not in database)
* IEA Faster Transition Scenarios (SDS to net-zero, in database)
The CO₂ emissions from energy & industry (not LUC) for the two IEA scenarios are rather similar to the 1.5°C with no or low overshoot
* IEA B2DS is roughly consistent with 1.75°C warming in 2100 (though, #SR15 does not assess this)
* IEA Faster Transition is assessed as 2°C
Read 15 tweets
How have CO₂ emissions developed compared to previous generations of emission scenarios?

Here is an update of our earlier comparisons

For fossil CO₂ emissions, we started to move onto track, but that quickly changed…

For total CO₂ emissions, including land-use change, we are much closer to the high end scenarios. This suggests we have been pretty bad at modelling land-use change moving forward...
We have not updated the AR5 scenarios for a few years (it is a bit of work to touch up with Illustrator), but emissions are certainly in the higher end. Many AR5 scenarios started climate policy in 2010, which didn't happen in reality, so a gap expected!…
Read 5 tweets
Even 1.5°C scenarios with "no or low overshoot" have CO₂ removal (negative emissions), & I suspect at a scale that many are uncomfortable with...

How many realise this? Do people equate "no overshoot" with "no negative CO₂ removal"?

The 9 scenarios in #SR15 classified as "no overshoot" hit zero around 2050 & go *net* negative to the tune of about 5-15GtCO₂ in 2100. The actual CO₂ removal *gross* negative emissions is much larger than that.

This was one of the key messages from "The trouble with negative emissions" article with @KevinClimate. The actual CO₂ removal (light orange) is much larger than commonly perceived (black line), as scenarios are generally plotted as "net" emissions!

Read 4 tweets
So I tried raising #ClimateBreakdown with in-laws this holiday. Context: they are working-class, self-educated, ethics of individual responsibility, enjoying in retirement what they never had as children or adults: leisure and travel.
My in-laws basically embody this excellent thread by @FlightFree2019. They are also resentful of me (educated, uni-job parents, uni-job myself) giving any advice or lecturing. Somewhat understandable. Uneasy truce over shared love of their grandchild. 2/
So yesterday we had a quick chat during TV commercials (SO MANY OF WHICH WERE ABOUT BOOKING FLIGHT-BASED HOLIDAYS). They said that "everyone knows" about #ClimateBreakdown but no one will do anything until "millions die, here, where it matters." 3/
Read 11 tweets
Following #cop24, check the storylines we derived in the @IPCC_CH #SR15 report for possible futures at a) +1.5°C without overshoot, b) +2°C, and c) +3°C. They start in 2020, when the #ParisAgreement comes into force. We have 2 critical years ahead.…
For full report (still proofs version), see:… (checked with @anna_pirani that it was ok to share the text of the storylines here!). @valmasdel
These storylines were developed with @JoeriRogelj, Roland Seferian @meteofrance, Myles Allen @ecioxford, Marcos Bruckeridge, @kristie_ebi, @oveHG, Richard Millar, Tony Payne @Bristol_Glac, @PetraTschakert, Rachel Warren @TyndallCentre, @NevilleREllis, Richard Wartenburger @eth.
Read 5 tweets
Does model bias effect outcomes of the #IPCC 1.5°C emission scenarios #SR15?

The scenario database is over represented by some model frameworks. Taking statistics will over represent some models (eg, REMIND, AIM), discount others (eg @IEA), & not all models included!

The bias varies by scenario category, here for 1.5°C scenarios with "no or low overshoot" as highlighted in #SR15. Should REMIND & POLES get more weight then GCAM or MERGE?
I often take medians of scenarios to simplify communication, trying to reveal the "key characteristics" of 1.5°C (trying to find robust messages). The scenario community does not like this approach
Read 8 tweets
THREAD (illustrative scenarios):

The #IPCC Special Report on 1.5°C #SR15 highlighted 4 illustrative scenarios. They vary widely in
* Socioeconomic assumptions (SSP1, SSP2, SSP5)
* Total (primary) energy use
* Biomass
* Solar
* Nuclear
* Oil
This is how the illustrative scenarios are presented in the #SR15 SPM. The energy system is shown by the table, the figures seem to give the key characteristics. It seems the selection was based on the use of biomass. 2/
P1 (LED) & P2 (S1) have the lowest use of biomass across scenarios, P4 (S5) has the highest use of biomass. They are outliers, which was perhaps the point of the selection? Because they are outliers, they potentially give a skewed perception of how most models get to 1.5°C! 3/
Read 10 tweets
THREAD (Nuclear in IPCC Special Report on 1.5°C)

When plotting all scenarios in the #SR15 database, it looks like nuclear may have a rosy future. But a closer look shows it is a more complex picture... 1/6
Plotting the additional nuclear over the baseline scenario (scenario minus baseline) reveals:
* nuclear does not change much relative to the baseline in most scenarios
* nuclear has solid growth in some scenarios 2/6
It turns out that the scenarios with solid growth in nuclear come from two models GCAM & MESSAGE. Here are model & scenario combinations with highest nuclear growth (42 listed). This lifts the median & gives impression of a more positive future for nuclear. 3/
Read 6 tweets
THREAD (on temperature, overshoot, & afforestation in #SR15)

In this thread I group a few nice (ie, unreadable) Twitter discussions on a few intriguing aspects of the Special Report on 1.5°C:
* What is "no overshoot"?
* What is "temperature"?
* Land impacts of afforestation? 1/
The SPM to the IPCC Special Report on 1.5°C highlighted 4 illustrative scenarios. This is fine. Three scenarios are called "no or limited overshoot". But, why are they grouped as "no or limited overshoot", & not as "no overshoot" or "limited overshoot"? 2/
(Aside: In Chapter 2, the illustrative scenarios are labelled LED, S1, S2, S3, in the Summary for Policy Makers they are labelled P1, P2, P3, P4) /2b
Read 15 tweets
When I hear ppl saying that we need systems change and not culture change to address #climate breakdown, I think ppl overstate the ability of top down law reform to change culture. Law reform is not particularly effective and changing culture. 1/
Guess what - the 13th, 14th, and 15th amendments did not achieve the end of slavery, equality, or the right to vote for African Americans. Slave state culture maintained near total African servitude, inequality, and vote suppression for a century b/c it was in the culture. 2/
Prohibition was written into the constitution. People did not stop drinking b/c it was in the culture, and the temperance forces didn’t give resources to enforce prohibition b/c it drinking really didn’t affect them except philospophically. 3/
Read 6 tweets
My take-aways from one of the first formal gatherings of climate scientists and humanitarians in Geneva, in the wake of the @IPCC_CH report highlighting the human impacts of 2˚ of global warming. #StepUp2018 #SR15 #Talanoa4Ambition #ClimateRedi @UNFCCC 0/15
1/ Forget about coral reefs & polar bears. The difference between 1.5˚ and 2˚of warming is 60 million more people exposed to severe drought; millions more potentially exposed to flooding, 23% more of the world's population exposed to extreme heat. This stuff is real.
2/ For small-island states at risk of being wiped off the map, limiting warming to 1.5˚ was already "the ultimate compromise". "We knew that 1˚ would jeopardize our ability to live on these islands,” a Marshall Islands rep said. “Anything beyond 1.5 is simply uninhabitable.”
Read 16 tweets
This is important, and it's of a piece. As clear as the #SR15 report was on the rapid physical transformation needed to avoid #climatebreakdown, it was almost silent on the political parameters of that transformation - but these are well researched. 1/?
As @TimmonsRoberts says, “It leaves readers and policy makers without tools to address the problem in the real world.”
So the big gap in #SR15 is one of covering the political realities surrounding climate change: these include the biggest barriers & best avenues for action. 2/?
That's quite a gap! Climate denial, as an action of the fossil fuel industry, has been wildly successful, weaponizing both scientific processes and media discourses. And divestment, extraction bans, legal actions have had arguably more success than techno-econ fixes. 3/?
Read 11 tweets
ICYMI: A big week for #GreenBonds & climate finance, with the #SR15 reminding us of the urgency to scale up green investment. In this string we’ll point to some of the events & moments from around the world that we’ve captured since Monday.
ICYMI: India: Giant state bank #SBI made a US$650m splash in the #greenbonds pool with inaugural issuance, funding #wind & #solar. In our special Post we profiled the bond, @SGX listing, asked when are more of global Top 100 Banks going to issue green.…
Still in India: our CEO @seankidney takes some time out for longer form interview with Priya Sreenivasan from @down2earthindia. Shares his [forthright] views on the $US7billion domestic #greenbonds market & its outlook. Worth the read.…
Read 18 tweets

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