Discover and read the best of Twitter Threads about #IPCC

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THREAD on Carbon Budgets

The 'Carbon Budget' is the cumulative CO₂ emissions from one point in time to another given a temperature limit, such as exceeding 1.5°C, reaching net-zero (~peak temperature), or to (say) 2100 for a 1.5°C scenario.…
2. The #IPCC #SR15 had different categories of scenarios.

The 'Below 1.5°C' scenarios never exceeded 1.5°C (no 'exceed' budget), but they all reach net-zero CO₂ emissions leading to a 'net-zero' or 'peak' budget (as peak cumulative CO₂ occurs at net-zero CO₂ emissions).
3. Most 1.5°C scenarios exceed 1.5°C, reach a peak temperature (over 1.5°C), & then decline back below 1.5°C (peak & decline scenarios).

How to define the budget? A net-zero budget is a clear definition, but corresponds to ~peak temperature (eg 1.7°C) & varies a factor of two!
Read 9 tweets
I’m trying to lose weight, which is kind of like trying to address #climatechange. I made a bunch of pledges to myself at my very own COP35 before Christmas 2019. But how can I do it, and will I succeed? 1/11
A diet is about finding the right balance between energy demand and supply. I can reduce my consumption, switch to healthier fuels (less ‘fossil’ varieties, more ‘greens’). I can also exercise, making everything more #energyefficient. Setting targets is also important. 2/11
But by golly, it’s hard to fit all this in when I also have to maintain a job, an apartment, pay bills, keep relationships… there’s more to life than fretting about the climate (um, I mean, my health). 3/11
Read 11 tweets
New paper with @piersforster now out in @NatureClimate - Energy budget constraints on historical radiative forcing…

Provides a top down energy budget constraint on historical radiative forcing of 2.3 (1.7 to 3.0) [5-95%] Wm-2. Thread: [1/n]
Radiative forcing is a fundamental quantity for understanding the drivers of climate change, yet significant uncertainty remains in our quantification & model representation of it. For example see any paper that includes @gunnarmy including this epic… [2/n]
What we do is combine measurements of historical temperature change dT & Earths heat uptake dN alongside model reconstructions of Earth’s radiative response Y. Constrains historical forcing F via energy budget eqn F=dN+YdT. Like Otto etal… in reverse [3/n]
Read 15 tweets
We just published a paper on climate sensitivity in #CMIP6 models:…

Figured it was time for my first twitter thread!
We found that effective climate sensitivity (#ECS), when averaged across all #CMIP6 models* (orange), was larger than in #CMIP5 (blue) by about 0.6 deg C (about 1 deg F).

*that were available by the end of 2019
This is mostly (but not entirely) due to stronger positive feedbacks from changes in low-level clouds. That is, most models predict that as Earth warms, cloud properties change so as to allow more sunlight to be absorbed, causing additional heating & ultimately more warming.
Read 21 tweets
It’s a bit overdue, but I did promise to write a report on my trip to China, to attend #IPHC23. (23rd International Passive House Conference.) Here it is.... as long, and probably rambling,🧵.
I’ll break my #iphc23 report into chapters: 1. Plenary & Policy Overview, 2. Conference presentations, 3. Expo, followed by 4. An editorial. (And perhaps some highlights of the short vacation I took afterwards to #Xinjiang, if I have time.)
1. Plenary & Policy: it was clear from the first moment I landed in Beijing that this event would not be a typical #Passivhaus conference. The Chinese Gov rolled out the red carpet, not just for practitioners, but as an all out International trade event. #IPHC23
Read 40 tweets
My analysis on potential #runawayclimatechange and the #IPCC goal of 1.5-2C target
And why/how i expect nasty surprises soon
First, a chart with trend lines showing warming speeding up
#methane #permafrost #arctic #antarctica
#ClimateCrisis #climatechange #gretathunberg
A few charts showing #breakout of temperatures, or potential #runawayclimatechange in 2019, from #alaska to #california or #europe
#ClimateAction #climatechange #gretathunberg
Why warmer soon? several factors
1/ the SUN
Sun is waking up, with solar spots appearing , and the solar minimum period is ending , with a weak solar maximum expected in 2023 .
Lagging time: 4 years
#sun #solarcycle #solarminimum…
Read 17 tweets
New Royal Society climate briefings outline what two IPCC special reports mean for the UK. They examine the links between land and climate change, and the warming climate’s effects on the oceans and ice-covered parts of the Earth: #IPCC
Sea level change will be one of the major impacts of climate change on the UK. @theCCCuk has said that the UK’s current coastal adaptations are insufficient considering sea level rise of at least 1m is a “near certainty” – perhaps before 2100.
@theCCCuk Around 72% of the UK’s land area is used for agriculture, so improving land use and management practices will be "critical” to achieving the goal of #NetZero by 2050.
Read 4 tweets
#Klimaleugner behaupten immer wieder, die #Klimamodelle seien falsch, bzw. unzuverlässig.
Vor dem Hintergrund, dass in den #IPCC-Berichten regelmäßig von Unsicherheiten die Rede ist, erscheint das manchen sogar plausibel.
Aber: Stimmt das wirklich?
Ein Thread. 1/15
Zunächst eine Definition: Mit #Klimaleugner meine ich die Leugner des anthropogenen, also menschengemachten Anteils am #Klimawandel.
Aber nun zum eigentlichen Inhalt: den Klimamodellen. Konkret handelt es sich um mathematische Modelle. 2/15
Mathematische Modelle sind vereinfachte Abbildungen der Realität. Insofern können sie niemals exakt sein.
Das müssen sie aber auch nicht: eine hinreichende Genauigkeit reicht völlig aus, um verlässliche Aussagen zu treffen. 3/15
Read 16 tweets
The #IPCC 1.5°C Special Report #SR15 used four illustrative pathways that varied by BECCS.

They all have considerable land-use change: 1500 million hectares is 4.5 India's!

If they don't have large-scale BECCS, they have large-scale afforestation. Land impacts unavoidable.

These are the four illustrative pathways. From left to right, they have more and more BECCS (yellow), though this does not correlate with land areas or impacts

From SPM

The #IPCC Special Report on Climate Change & Land #SRCCL says that BECCS is bad at scale (red), while afforestation is good (blue) across all dimensions but food security

But, if "best practice" is used, the BECCS & afforestation seem to be a win-win-win-win. Hmmm...

Read 5 tweets
The Nationally Determined Contributions (NDCs) submitted under the Paris Agreement would not limit global warming to 1.5°C, even with very challenging increases in the scale & ambition of emissions reductions after 2030.
This is one of the key messages from #IPCC #SR15, saying that current emission pledges make 1.5°C infeasible. The figure is from Chapter 4.

I am not sure if that point comes across very clearly with the figure (I added the red boxes) and the dense text. Thoughts?
Also a little curious that the uncertainty range for 1.5C with high overshoot only shows the 25-75% range, so presumably there are scenarios that can get to 1.5C from the NDCs?
Read 3 tweets
For weeks and months, i have been tracking the arctic temperatures and the decline of the icecap.
Wondering why it was so warm , and for so long.
What is happening there? Icecap is down over 50%.
Albedo effect will be massively impacted by this.
#climatechange #gretathunberg
We learned a few days ago, that scientific expedition in the east siberian arctic just found methane fountains bubbling on the sea surface , in the middle of the east siberian sea.
Some of the implications :

#ClimateCrisis #climatestrike #ClimateAction…
Here is the theory:
1/ Increasing periods of open water implies an increasing number of storm events.. Such events have the potential to rapidly ventilate bubble-transported and dissolved CH4 from the water column, producing high emission rates to the atmosphere
Read 14 tweets
A dark tweet, sorry about this.
We learned yesterday that scientific expedition in the east siberian arctic just found methane fountains bubbling on the sea surface .
#ClimateCrisis #climatestrike #ClimateAction #climatechange #gretathunberg…
Please watch the video and focus on what the russian scientist declares (13.20-14-20)
Dr Natalia Shakhova
#ClimateCrisis #climatestrike #ClimateAction #climatechange #gretathunberg #methane

Natalia Shakhova doesn't agree with the #ipcc, which doesn't take the ESAS risk into account for calculating the various #RCP ..or any feedback loops including #CH4

You can read more here…
Read 7 tweets
India has pledge to reduce its emission intensity (CO₂/GDP) 33-35% from 2005 levels by 2030, leading to a big rise in CO₂ emissions by 2030.

In context, 1.5°C requires a 45% reduction in CO₂ emissions from 2010 levels by 2030, globally!…
Yes, India has much lower per capita CO₂ emissions than many countries & is below the world average. But, if 1.5°C or 2°C is the goal, then even countries with low per capita emissions have to reduce emissions...

Yes, US, EU, etc have to do more, so does India, China, etc

Despite impressive growth in solar & wind in India, see lines at the bottom of figure, the Indian energy system is dominated by coal, oil, & biomass.

Coal is still growing strongly in India, despite claims that Indian coal has come to an end.

Read 4 tweets
1. The #IPCC has released another Special Report, this time on the Ocean & Cryosphere in a Changing Climate #SROCC.

Oceans (top) & mountain & polar regions (bottom) all have pretty severe impacts.

About the only benefit is for Arctic shipping & kelp!
2. The report's headlines focus on RCP8.5 (red) versus RCP2.6 (blue), "reflecting the available literature".

Reality will lie somewhere in between these two extremes, but important to highlight that changes relative to the recent situation (1986-2005) are already extreme...
3. "RCP8.5 is a high GHG emission scenario in the absence of [climate] policies... Compared to the total set of RCPs, RCP8.5 corresponds to the pathway with the highest GHG emissions."

True, but RCP8.5 is an extreme baseline & many think implausible...…
Read 8 tweets
#BREAKING Climate: Tropical cyclones becoming more powerful, destructive: UN report
#BREAKING Many coastal megacities to be hit annually by extreme weather by 2050: UN report
#BREAKING Building dikes and levees to hold back rising seas could cost hundreds of billions of dollars a year: UN report
Read 6 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
El #CO2 representa un 0.52% sobre el total de todos los gases que confinguran las distintas capas de la atmósfera terrestre. Las emisiones de orígen antropológico representan una parte muy pequeña respecto del total.
En EE UU (donde la medición de la temperatura terrestre es más precisa), las variaciones de temperatura en los últimos años son menores y sin tendencia clara (más bien, algo a la baja).
Dos de los gráficos del informe del #IPCC (de 2007, luego se eliminaron de sucesivos informes) son los que muestran una evolución largo plazo: la Tierra ha estado mucho más caliente (y más fría) que el nivel de temperatura actual.
Read 16 tweets
The sun has always been the best antidepressant. It is especially potent against (un)consciously (agitated-depressive) science-denying sun-, cosmic rays-, clouds- & ocean- (low-pass filter of the climate system because of their heat content) deniers in #IPCC.
An insight into the agitated-depressive world of a physicist seeing CO2 as "inevitable byproduct of combustion" and not as the source of life
While (agitated-depressive) science-denying sun-, cosmic rays-, clouds- and ocean-deniers such as these Swiss #IPCC-"scientists" are still predicting the end of all glaciers in Switzerland by 2100...
Read 15 tweets
Too busy, or need poetry? Here’s the #IPCC’s Special Report on Climate Change and Land #SRCCL summarised in 29 #haiku #sciku. (Disclaimer: personal choices here, not representing the same balance as the full report. Apologies for misappropriating this ancient art form…) [1/29]
SPM Section A1.1 [2/29]
SPM Section A1.3 [3/29]
Read 30 tweets
The #IPCC special report on the land sector is out.

It's the culmination of the hard work of 107 experts from 52 countries.

I've got some big takeaways. Buckle in – it's going to be a long thread.

Some quick background:

Land and ocean warm at different rates (thank you @RARohde) for the great figure.
Land is both a carbon source and sink. The balance between the strength of sources and sinks determines overall impact of land on GHG emissions. Humans already use a LOT of land (almost ¾ of all ice-free terrestrial surface, according to the IPCC graphic below).
Read 24 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
Takeaways from the #IPCC Special Report on #ClimateChange & Land (#SRCCL). A thread.

1) We use a lot of land (much unsustainably)

Humans directly affect ~72% of "global ice-free land surface" & all is impacted by climate change (e.g. through warming & more intense extremes

2) A two-way interaction

Our use of land drives #ClimateChange ("agriculture, forestry and other land use" are ~23% of global man-made GHG emissions) & climate change adds stresses so worsens existing risks (e.g. biodiversity & degradation from extremes events)

3) As well as being an emission source, land is a sink

Photosynthesis draws down carbon dioxide from the atmosphere and fixes it in plants (and soils). Overall the land is a net sink of ~29% of total human-induced CO2 emissions.

Read 9 tweets

The next #IPCC Special Report is out, this time on climate change & land (#SRCCL).

There is plenty to digest over the coming days, weeks, months, years, but a few initial reactions from the SPM...

Just to set the scene, no pressure: "Land provides the principal basis for human livelihoods and well-being including the supply of food, freshwater and multiple other ecosystem services, as well as biodiversity." Land is already heavily impacted...
Agriculture, Forestry, & Other Land Uses (AFOLU) are a quarter of global GHG emissions (GWP100).

The natural response of land to human-induced environmental change has been to cause a sink of ~11.2GtCO₂/yr, 29% of global CO₂. This may not last with climate change.

Read 12 tweets
Has a 10-fold increase in trade increased energy & material demand?

If we did not trade, it is quite possible that environmental impacts would be worse. No trade may lead to inefficient domestic resource extraction (food) & greatly limit technology.

If we did not trade, we would not have rapid price declines in solar or the emergence of electric vehicles. We would probably drive inefficient fuel guzzling 1970 style cars. We would probably have much more inefficient food production, causing biodiversity loss. 2/
That is not to say trade has no impact, but trade is probably an important part of the "solution" particularly related to technological transfer & development. North Korea has very limited trade, & that probably serves as a good (extreme) example of the alternative. 3/
Read 5 tweets

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