Expected temperature increase if all fossil fuel emissions eliminated today

[br...@chesdata.com]

This is an impossible scenario, but it gives an idea of the magnitude of the temperature increase “baked in” due to historical emissions.

 

I used a desktop version of MAGICC (a reduced complexity Earth system model that has been widely used in climate science for over three decades, most notably in multiple IPCC reports)

 

The analysis is based on RCP4.5 where there are no CO2 emissions from fossil fuels after 2025

 

Unknowns: albedo change, changes to land and ocean sinks, etc.

 

Take away: we should expect another 0.25⁰C of warming from the historical emissions (data in the attached spreadsheet)

 

[robert...@gmail.com]

Hi Bruce

I haven't looked at your email in detail so it may be little more than a typo, but annual CO2 emissions under RCP4.5 do not cease in 2025.  They peak at ~42Gt in 2040s and then decline gradually to ~2.5Gt by 2300.

Regards

Robert

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[rob...@rtulip.net]

Thanks Bruce.  About “Unknowns: albedo change, changes to land and ocean sinks, etc.”, surely these are likely to cause more warming than direct greenhouse forcings?

 

We now seem to be in a situation where these accelerating feedbacks exceed forcings as sources of heat.

 

When an avalanche is starting it is not a good bet that it might slow down.

 

Regards

 

Robert Tulip

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[rob de laet]

Hi everybody, 

as usual people keep the tunnel vision focus only on the GHG blanket, not on the workings of the Earth's airconditioning systems (intact ecosystems, particularly living oceans and tropical rainforests. 

HOW MUCH IS NEEDED TO STABILIZE TEMPERATURES AT CURRENT LEVELS?

Stabilizing global temperatures around 1.5°C requires closing the current energy imbalance of roughly 1.8 W/m² through a combination of carbon drawdown and reactivating the Earth’s natural cooling systems. From our work, restoring on the order of 2.7–2.8 million km² of tropical rainforest, alongside strict protection of remaining intact forests, can generate approximately 0.9°C of global cooling through intensified evapotranspiration, increased cloud formation, and enhanced export of latent heat to space. If we could start with a total moratorium on prime forest destruction and rebuild the destroyed forest areas on say 1 mio km² of recently destroyed forests, that would go a long way to push the heating curve down, including a carbon sequestration capacity of around 15–20 GtC translating into 7–9 ppm CO₂. 

In parallel, rebuilding around 200–300 GtC of biomass worldwide would reduce atmospheric CO₂ toward roughly 350–360 ppm, contributing on the order of 0.8–1.0 W/m² of reduced radiative forcing. Complementing these land-based effects, large-scale restoration of ocean biology across approximately millions of km² could enhance marine cloud formation and brightness, increasing ocean albedo. 

A back-of-the-envelope estimate is that boosting low cloud cover by 1 percentage-point could cool the planet by roughly 0.1–0.3°C over the next few decades and about 0.2–0.5°C longer-term, with a stronger effect if the increase is concentrated in the tropics, but at the same time regenerating the most biologically active ocean areas like the Southern Ocean (krill) would have an amplified effect on the whole dynamics of ocean biology, phytoplankton and zooplankton bloom with additional carbon take down and increased cloud cover. Customized ocean pasture regeneration could have outsized and multiple effects. 

If we combine these actions they will also have weather extreme mitigation effects, restore soils, aquifers, calm the drought/flood cycles, decreasing hits on our food production. 

So a combined strategy to restore the biosphere, while phasing out FF is by far the smartest strategy to get us out of our mess and it is affordable too in terms of investments. Now we only have to convince the world that this can work even within their time horizons. If we could find some finance to bring a team together to work out a detailed plan to convince the world that we can actually reverse the climate crisis fast, that would be great. 

Best,

Rob de Laet 

Project Lead Cooling the Climate

Member of the EcoRestoration Alliance

Fellow of Global Evergreening Alliance

Fellow fo the Schumacher Institute

Planetary Solvency Taskforce

Co-founder of Senang Eco Services

WhatsApp: +55 71 992617846

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[Jan Umsonst]

Yep yep yep!

Our biggest problem is that the oceans now shift their cooling function to a warming function or in other words in the past ocean heat uptake slowed down global warming, now its accelerating it

Its a climate atrocity under way which is not foreseen in the models as the expansion, intensification and persistence of marine heatwaves is driven by highly dynamical regional processes, cloud cover changes (models are here not too good - feedback's), and distinct patterns of ocean heat uptake (e.g. formation of warm blobs of warm water, or in other regions warming mostly confined to the upper 200m 300m-400m), and stratification changes as the specific pattern - vertical distribution of stratification changes and their strength defines how much more energy is needed to mix the oceans - all small scale processes ocean mixing with fast changing conditions possible - e.g. heavy precipitation and the formation of barrier layers in the oceans (brackish surface water layer - or even in a layer subsurface if the precipitation is too strong).

Its important to understand that while over the horizontal the oceans are thousands of kilometers wide, but over the vertical where it clouds they are "just" 700m deep...

All the best

Jan

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[robert...@gmail.com]

Hi all

I am getting very confused about the focus on albedo by some within this group.  It seems to me to be based on a misunderstanding about how albedo changes are reflected in climate models.  I’d like to unpick this because if I’m wrong, which as we all know, is not impossible, I need radically to change my thinking about global warming.  Conversely, if I’m right, others might need to do so.

Let me explain where I’m coming from.  I welcome corrections.

Albedo changes are either forcings or feedbacks, the distinction being whether they arise independently of global warming or are caused by it.  So, for example, albedo change from land use change is a forcing, whereas albedo change from reduced ice sheets is a feedback.  The distinction is important because the warming caused by feedbacks is built into the Equilibrium Climate Sensitivity (ECS) used as an input parameter in simple climate models (SCMs) like MAGICC and FaIR.  Forcing from albedo changes unrelated to warming must be input separately into such models.  Complex models use the same basic energy balance principles, but the global picture is arrived at by aggregating details computed locally in latitude, height, or grid cells, with explicit terms for shortwave absorption, longwave emission, and non‑radiative fluxes.  The formulae used in SCMs are ‘tuned’ to deliver results that closely approximate those from an ensemble of complex climate models.

The first thing to note is that in the real world, as Hansen explains in his Pipeline paper, the warming from feedbacks is about 70% of the total warming from atmospheric CO₂, i.e. more than double the direct warming.  Moreover, the feedback warming emerges later because it can’t emerge until the direct warming has triggered it - for example the melting of the ice sheets, which takes some time.  By the time the feedback warming kicks in, the direct warming will have subsided.  It should, therefore, be expected that as the atmospheric GHG concentration builds up, warming due to feedbacks will accelerate and become a larger proportion of total current warming.

We can be confident that SCMs capture reasonably accurately the feedback warming. both as to extent and timing, because they reconstruct accurately today’s current surface temperature from historical emissions data since 1750.  However, as Hansen notes, there is good reason to suppose that ECS is closer to 4.5^oC than the conventional value of ~3^oC used in these models.  He explains that the models are accurate because, while they have underestimated ECS they have also underestimated the forcing from aerosols; the two underestimates cancel each other out.

This means that when using SCMs to forecast the warming from future emissions scenarios, it is necessary to adjust both for the higher value of ECS and the higher value of aerosol forcing.  In addition, any scenario that includes albedo changes that are not feedbacks requires these to be explicitly defined as forcing inputs.  For example, the standard data inputs of MAGICC and FaIR do not include the additional forcing arising from the recent reduction of aerosols from shipping.  This must be added in if the forecasts are to be reliable.

It follows that when using SCMs, it is necessary to distinguish between the feedback and non-feedback forcing from albedo changes because only the latter need be explicitly input.  The former will automatically be accounted for so long as the values of ECS and aerosol forcing are correct.  There are different considerations in relation to complex climate models that are not relevant here.

If that explanation is correct, any comments about the current role of albedo forcing need to disentangle feedback and non-feedback forcings.  Feedback forcing needs to be addressed in relation to the value of ECS, and non-feedback forcing needs to be explained in relation to its source and care taken to include in the scenario the correct value of the forcing.  Without this approach, vague and generalised comments about the role of albedo change should be resisted as they are very likely to be misleading.

The reason SRM is now such a high priority has nothing to do with the increasing proportion of warming due to the loss of albedo.  It is simply because SRM is likely to be the quickest way to deliver the scale of negative forcing necessary to be sufficiently climatically significant to avert a climate induced catastrophe.  CO₂ is too radiatively inefficient for us to reduce its atmospheric concentration at sufficient scale and speed.  Reductions in non-CO₂ GHGs, in particular methane, could provide some assistance, but cannot deliver sufficient negative forcing on their own to reduce the burden on CO₂ to manageable levels.

That’s the narrative.  The numbers are also vital.  I’ll leave them for now but my view is that we cannot rely on being able to do sufficient SRM, even with political and social support, to be able to dispense with major reductions in CO₂ emissions if our objective is a substantial reduction in climate change risk.

Regards

RobertC

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[Sev Clarke]

Hi Robert,

Thanks for this excellent exposition. It makes much sense.

My proposed five climate intervention methods (Buoyant Flakes, Nanobubbles, AMRAerostats, Seatomisers and Ice Shields) would probably fall mainly under the forcing category, but would not these also have multiple feedback effects of their own, as well as regional combinatorial effects that might be used to our advantage?

Only do I content with one element in your last paragraph, as I do believe that together (and in combination with other selected methods) they would allow us to take our time (several decades) in reducing our emissions to near to net zero without causing great disruption - noting that some of the methods have parallel, greenhouse gas removal (GGR) capabilities and others which might reduce subsequent CO2 emissions from warmed land and sea.

Regards,

Sev 

<image001.png>

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[Michael MacCracken]

Well said. Mike

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[H simmens]

Robert,

Your explanation of the critical distinctions between forcing and feedbacks I would suspect is little known by even most climate aware individuals. 

It would be really helpful if someone with some graphic skills could take Robert’s explanation and turn it into a simple infographic that could be widely distributed. 

Herb

Herb Simmens

Author  of A Climate Vocabulary of the Future

“A wonderful achievement, a SciencePoem, an Inspiration, a Prophecy, also hilarious, Dive in and see"

 Kim Stanley Robinson

@herbsimmens

On Feb 28, 2026, at 7:56 PM, 'Michael MacCracken' via Healthy Planet Action Coalition (HPAC) <healthy-planet-...@googlegroups.com> wrote:



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[Clive Elsworth]

Thanks Robert

 

I agree with your analysis that includes that restoring/increasing albedo is by far the most cost-effective way to reduce global temperatures.

 

As regards climate feedbacks, once again water vapour is the main one, as exemplified by this recent message from Prof Alan Gadian (Meteorology, Leeds, UK) regarding Ron’s letter that says MCB could reduce global warming by 0.2°C / decade:

 

It is true. 0.2 degrees is quite a lot.  Yes, if you were to do the globe you could obtain another ice age.  If you do it in just 3 small areas yes you could compensate for double CO2 warming.  Latham and I argued we could return to preindustrial in maybe 20-30 years with 3-region seeding.  BUT ….

 

There is a problem.  Increases in water vapour now are just as much if not more a forcing as Double CO2 warming .  So, we’re now challenging to compensate for CO2 et al and water vapour. I would estimate we are now at least 0.2C per decade or more (controversial statement) … i.e. 0.2C decrease would be a huge achievement since it is clear fossil fuel emissions are increasing. 

 

So yes 0.2C decrease is a small amount, and it should be bigger if CO2 were the only problem ( e.g. tropical cloud cover as well).  We are in a desperate situation in reality, and so I do think the number would / should be bigger, BUT when you include water vapour heating, it is huge effect. 

 

Alan Gadian

 

(edited by me only for grammar only)

 

Clive

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