Consultation on SLR declaration, deadline 15th April

[John Nissen]

Dear Peter,

Here is another opportunity to highlight the high risk of a massive sea level rise this century.  I think we should take the opportunity, though the deadline is only a few days away.

Best wishes, John

https://www.iitc.org/declaration-on-sea-level-rise-global-online-stakeholder-consultation/

[Paul Klinkman]

As a rule, engineers always build to survive a reasonably worst-case scenario.  What is the 99% worst case scenario for sea level rise?  Why would anyone with integrity plan to barely survive a 50% median case scenario for sea level rise?

Yours,

Paul Klinkman

[Michael MacCracken]

Exactly--I've been told the phrase is "worst plausible" outcome, and just as engineers are taught to design to be resilient to that (e.g., once in a hundred year flood), I understand business leaders are taught likewise (banks to be run to be resilient to a run on the bank; insurance and reinsurance to disasters; and the US defense department wants a military capable of fighting simultaneous conflicts in the Atlantic and Pacific basins; etc.). For such planning, the worst plausible outcome is not the central estimate, and yet that is what is being done in response to climate change--IPCC focusing on the central, most likely values whereas one entities should be responding to (per their traditional approaches) is the something like what are listed as unlikely and even very unlikely, but still plausible. For sea level rise, this is likely something like persistent rates of several meters per century even if climate stabilization is achieved. And basically no groups are preparing for this.

The most reported IPCC metric, namely the average over the last decade or two of the change in global average temperature, is just not the metric that needs to be used to drive adaptation, mitigation, and other climate change policies.

Mike MacCracken

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[John Nissen]

Hi Mike,

This [1] could prove to be an important declaration from the UN, but it has to be obtained by consensus. The deadline for input is Wednesday 15th EDT.

In my view, the "worst plausible" outcome is over a metre of SLR by 2050 due to a partial collapse of the Greenland Ice Sheet and/or a collapse of one or two major Antarctic glaciers.  Even if not a metre of SLR by 2050, we could have several metres by 2100.  Remember that, 11.7 kya, the sea level rose 20 metres in 400 years, i.e. average 5 metres per century.

For many countries it may not be practical to defend against such SLR, especially if it happens suddenly.  I want the message to be that such a dangerous SLR might be avoided by emergency deployment of SAI to refreeze the Arctic and cool Antarctica.  It would be extremely foolish if the declaration did not mention the possibility of cooling intervention to save the day.  

Would you like to submit something with me?

Cheers, John

[1] https://sdgs.un.org/universal/sea-level-rise-declaration-2026-61065

Background

The General Assembly in its decision 78/558 of 1 August 2024 decided to hold a one-day high-level plenary meeting of the General Assembly, no later than the last day of the general debate of its eighty-first session, to further consider sea level rise.

The meeting aims to strengthen international cooperation and collective action to address sea level rise, including by supporting developing countries, particularly those most vulnerable to the adverse effects of climate change, as well as coastal communities, in building resilience and adapting to its consequences. The meeting will result, without setting a precedent for similar meetings, in a concise, action-oriented and intergovernmentally negotiated declaration agreed by consensus.

Announcement

In order to support an open, inclusive and transparent process, a global online stakeholder consultation will gather inputs from stakeholders, including civil society organizations, academic institutions, the scientific community, the private sector, philanthropic organizations, Indigenous Peoples and local communities, and other relevant actors. Inputs received through this consultation will be compiled and shared with the co-facilitators to inform the intergovernmental consultations on the declaration.

Submit your inputs here

The deadline for submissions is 15 April 2026 (COB, EDT). 

To view this discussion visit https://groups.google.com/d/msgid/planetary-restoration/01e985c8-03df-4a75-9de0-9ca0792f519c%40comcast.net.

[John Nissen]

Dear Peter,

Thanks for the input.  I've already produced a version which I hope captures the flavour of your concerns, though ecology wasn't on the menu.

I am submitting on behalf of PRAG, and we will have to quickly update the website with our detailed conclusions and plans.  This is what I will enter into the submission form unless there are some good suggestions (or serious objections) on any point within the next few hours.  These are the pieces of text for submission.  All are close to character count maximum.

URL of official website for more information

https://planetaryrestorationaction.group/

Question 1 – Knowledge, data and science to inform sea level rise risk assessments and decision‑making

The current global trend of 0.35C/decade would produce 2C global warming by 2040 and 4C by 2100. The Arctic is warming four times faster.  Greenland contains enough ice for >7m SLR.  The risk (probability x impact) from collapse of Greenland glaciers producing 0.5m SLR by 2050 leading to >2m by 2100 can be shown to be huge compared to the risk from cooling intervention to prevent such collapse.

Question 2 – Adaptation, finance and resilience in relation to sea level rise

Wealthy countries might prepare defences against a SLR of 0.5m by 2040.  But the cost of such defence would be unaffordable for many countries, so low-lying areas, including some dense conurbations, would have to be evacuated.  The mass migration caused would lead to huge tensions and aggravate conflict globally.  Measures to cool the Arctic to prevent such SLR should be a UN top priority.

Question 3 - Livelihoods, socioeconomic challenges and culture and heritage in relation to sea level rise

Some megacities, much cultural heritage and 20% of global population live in low-lying areas;     0.5m SLR would be catastrophic for livelihoods, social cohesion, economies and cultural heritage.  Every effort must be made to slow sea level rise, particularly where it is accelerating due to active tipping processes of polar meltdown, only stoppable by powerful cooling intervention.

Question 4 - Sea level rise and its legal dimensions

Countries have an obligation to protect their citizens.  But the only available means to prevent catastrophic SLR is through Stratospheric Aerosol Injection (SAI), only implementable by a few of the wealthiest countries.  International collaboration of these countries should be legally mandated for the rapid deployment of SAI to help protect everyone vulnerable to SLR, wherever they be.

Name of good practice

Deploy stratospheric aerosol injection to lower Arctic temperature and halt its accelerated meltdown

In your view, what are the top three drivers of its effectiveness? 

1. Geophysics and paleoclimate research has established that cooling the Arctic and sub-Arctic surface water would slow the meltdown of Arctic glaciers; any delay to cooling deployment would increase the risk of irreversible ice mass loss leading inevitably to many metres of SLR.

2. Research suggests SAI can be ramped up to start lowering the Arctic temperature within years rather than decades; adverse side-effects seem manageable. 

3. Arctic cooling offers major climate benefits: slowing the release of greenhouse gases from permafrost; reversing the trend towards ever more extreme weather; and avoiding a catastrophic AMOC collapse.  These huge benefits could help persuade people of the extraordinary opportunity which rapid SAI deployment provides, besides slowing SLR.

Best wishes, John

On Tue, Apr 14, 2026 at 11:05 PM Peter Wadhams <peter....@gmail.com> wrote:

Dear John,

1. Absolutely, reply is vital, 

2. Points to make

3. Whole host of reasons why we should be terrified of an accelerated rate of SLR.

Examples are:

a. Warm water penetration under polar ice sheets leading to break up of complete sheets, 

mass fluxes and enhanced glacier flow;

b.Changed ocean circulation gives increased ocean to atmosphere heat flux;

c.Increased flow rate of mountain glaciers.

If the flow is enhanced for this or other reasons, we can expect:

1.Worldwide floods;

2.Loss of low level land especially rice crops;

3.Ecolgical catastrophes.

We have to preserve our ice!

Sorry I can't do more. I can volunteer to look at what you write in the form, before sending it.

Regards,

Peter

On Tue, 14 Apr 2026 at 17:01, John Nissen <johnnis...@gmail.com> wrote:

Dear Peter,

I've not heard from you recently.  I hope you are well.

What do you think about a contribution in response to this call?  Mike isn't able to help, but gives some advice to follow.  We've only got today and tomorrow to get a submission in.  But, having both been involved in giving evidence to the UK Environment Audit Committee, we should have some credibility.

Best wishes, John

---------- Forwarded message ---------
From: Michael MacCracken <mmac...@comcast.net>
Date: Tue, Apr 14, 2026 at 12:43 AM
Subject: Re: [prag] Re: Consultation on SLR declaration, deadline 15th April
To: John Nissen <johnnis...@gmail.com>

Hi John--I'm off on vacation and just won't have the time to work on something in response to this call by the time of due date. My only suggestion based on your comment would be to be a bit more conservative on the amount. As I recall, the dashed line of the upward possibility in the AR6 came out at 2 or m by 2100. Work off of that and take half or so and spread out over the century just so your are not viewed as dismiss-able doomsayer. Half a meter by 2050 is not impossible but the key point then is that the rate will very likely accelerate and continue to grow. What aggressive SAI could do is likely first slow the acceleration and by 2100 perhaps get it to below today's rate--completely stopping calving will be unlikely, but making it so more snow falls on the ice sheets will be critical, and likely given there are warm ocean waters to evaporate moisture and precipitate out as snow and then cold surfaces to reduce summertime loss--that is how the Milankovich orbital mechanism worked to build up snow (warm winters and cools summers). So, try to stick to lessons and numbers from credible sources--you should be able to make a good case.

And sorry, but family vacation interactions have to have priority for family peace.

Best, Mike 

[John Nissen]

Oops,

Under Qn 2, I should have "Wealthy countries might prepare defences for 0.5m by 2050" not 2040.  There is a risk of 0.5m by 2040, but it is not as well accepted, so I have taken Mike's advice to be on the conservative side.

Your points, Peter, can go in a new entry on the website especially concerned with sea level rise.  Note that sea level rise is a security threat for the UK, which is seeking comment on their security strategy: deadline soon.  Could you help me with a submission?

I haven't mentioned anything about IPCC deliberations and hopes.  I don't know if I can slip anything in.  I would like to repeat somebody's observation that there's enough GHG in the atmosphere to guarantee the complete loss of polar ice.

Cheers, John

P.S. I checked up on the 20% figure for populations at risk and got this from google AI:

Approximately 11% of the world's population, or nearly 900 million people, live in low-elevation coastal zones (LECZ) less than 10 meters above sea level. This number is projected to exceed 1 billion by 2050. A broader analysis indicates that 1.47 billion people (roughly 19% of the world's population) are exposed to significant flood risk.

P.P.S.  There is also the global cost estimate of $700 billion per year for a one metre rise, which I used in my letter to the FT, thanks to John Moore.

 

[John Nissen]

Attached are the final text pieces in answer to their questions, carefully copied onto their form and sent half an hour ago.  I added a bit about future temperatures "while CO2e ppm remains high".

The link to the saved form is long and you may find you cannot access it.

https://forms.office.com/Pages/ResponseDetailPage.aspx?id=2zWeD09UYE-9zF6kFubccJ1YhGewNmhKnVgj4-jHCw9UNUpUVUlHM1RIMUJGTk8wQURXWlZKQ0xXSS4u&rid=262&GetResponseToken=TMLts0O1SPqRLWhtMZh6Pu--nSzBCFinHE5S1BxXV1U&origin=rc&prevsubpage=rcfre&d1obforrc=1&rcsidebar=0

Cheers, John