tipping points – The Green Tau

Counting on … day 204

15th December 2025

What is AMOC?

AMOC, the Atlantic Meridional Overturning Circulation, is a system of ocean currents that help distribute warm water around the world. (1)

I wrote about this last month – https://greentau.org/2025/11/18/counting-on-189/ – but want to recommend Professor Tim Lenton’s address at the National Emergency Briefing which illustrates vividly the impact if AMOC fails: https://youtu.be/tmd6MDiJmQU?si=RcnuJIDqMeJHirD5

Research, which is still on going, suggests that the topping point which will make the collapse of AMOC inevitable could be passed in the next few decades – but the resulting collapse of the system might take another 50-100 years to happen. Even keeping the global temperature rise to the 1.5C Paris target is now predicted to carry a 10-25% risk of reaching this tipping point before the end of the century. It is a risk we cannot afford to take given the impact it will have on the viability of human life – even if that will not effect us now, it will effect future generations, our children and our children’s children. (2)

https://weather.metoffice.gov.uk/binaries/content/assets/metofficegovuk/pdf/research/climate-science/met-office-hadley-centre/amoc-factsheet-update-2025-v3.pdf

(2) https://www.theguardian.com/environment/2025/aug/28/collapse-critical-atlantic-current-amoc-no-longer-low-likelihood-study?CMP=Share_iOSApp_Other

And also https://www.theguardian.com/environment/2024/oct/23/we-dont-know-where-the-tipping-point-is-climate-expert-on-potential-collapse-of-atlantic-circulation?CMP=Share_iOSApp_Other

Counting on … day 202

11th December 2025

What is a tipping point?

From the Met Office “In the context of climate science, a tipping point refers to a critical threshold in the earth’s system or related processes which, if passed, can cause sudden, dramatic or even irreversible changes to some of the earth’s largest systems, such as the Antarctic ice sheet or the Amazon rainforest.” (1)

And from the Natural History Museum: “Large areas of the world could soon become unrecognisable if global temperatures continue to rise. From the loss of coral reefs to the shutdown of major ocean currents, shifts in Earth’s climate and ecosystems will have untold consequences for billions of people across the world.” (2)

Tim Lennon, head of the Global Systems Institute at Exeter University p, spoke very eloquently on this issue at the recent National Emergency Briefing. You can see a recording here – https://youtu.be/tmd6MDiJmQU?si=goRIfzf8AhiriESi

Tipping points also work in the opposite direction. Just last year the last coal fired power station closed ahead of schedule as policies that encouraged the phasing out of coal reached that critical tipping point. Similar tipping points can also be seen in the cost fall and expansion of wind farms, solars panels and electric vehicles.

Counting on … day 201

10th December 2025

When planetary boundaries are once crossed, it is still possible to reverse the situation and restore the balance of the Earth’s systems. However the effect of crossing a planetary boundary may irreversibly impact delicate parts of the Earth’s ecosystems such as coral reefs.

These reefs are important because:-

They protect shorelines from strong ocean currents and prevent coastal erosion
They provide sheltered waters for many species of sea life.
They filter polluted water ensuring clean water for marine life and clean beaches
They sustain local fishing based communities and especially those located on low-lying islands
They absorb carbon dioxide

Coral reefs are being damaged by the acidification of the oceans – the depletion of calcium in the structure weakens them. They are also damaged by rising ocean temperatures which stress the corals causing them to expel the symbiotic algae that enable them to feed and which give them their distinctive colours – this is called coral bleaching. (1)

The multiple causes of damage to the world’s coral reefs has destroyed such a proportion that their future is now jeopardised. These reefs are loss of coral reefs on this scale means that we have passed one of the Earth’s systems tipping points. (2)

In the Caribbean, coral reefs have decreased by 48% since 1980. (3)

Info graphic https://oceanservice.noaa.gov/facts/coralreef-climate.html

(1) https://www.wwf.org.uk/coral-reefs-and-climate-change

(2) https://global-tipping-points.org/case-studies/#coral

(3) https://www.theguardian.com/environment/2025/dec/09/caribbean-reefs-have-lost-48-of-hard-coral-since-1980-study-finds?CMP=Share_iOSApp_Other

Counting on … 189

18th November 2025

Oceanic tipping points

The oceans redistribute cold and warm water across the globe influencing winds – both direction and intensity – and weather patterns. Ocean currents enable the flow of water from hotter to cooler areas (tropics to the poles) and by the flow of water between areas of higher to lower salt density. Here in the UK we particularly benefit from the warmth that the Atlantic currents bring giving us mild winters and year round rainfall.

The driving force for these ocean currents lies in the artic regions. The density of the cold, saline rich waters causes the waters here to sink and as they do this pulls in warmer waters from the tropics. However as sea ice and icecaps melt, so the water becomes less salty, and less inclined to sink, reducing the energy that pulls the oceanic currents. In the North Atlantic this driving force is known as the Atlantic Meridional Overturning Circulation or AMOC.

Here in the UK, our climate and weather patterns are highly dependent on the functioning of AMOC. If this slows or becomes unstable, it will impact temperature and rainfall patterns cross Europe and giving us in the UK and Northern Europe a much colder, wetter climate. And at the same time changing the climate in southern Europe, making it hotter and dryer.

This graphic comes from the IPCC 6th Assessment Report (https://www.ipcc.ch/report/ar6/wg1/figures/chapter-9/faq-9-3-figure-1)

Whilst there are signs that AMOC is weakening, it is hard for predict quite how quickly and to what degree it will change as global temperatures rise. On the other hand the potential damage a change in AMOC will cause, should make decision-makers focus on avoiding that as a matter of urgency.

“The risk of a critical AMOC transition is real and very serious, even if we cannot confidently predict when and whether this will happen. We have already left behind the stable Holocene climate in which humanity has thrived (Osman et al., 2021), and the latest IPCC report warns us that beyond 1.5°C of global warming, we move into the realm of “high risk” with respect to climate tipping points (IPCC, 2023).” (1)

(1) – https://tos.org/oceanography/article/is-the-atlantic-overturning-circulation-approaching-a-tipping-point

Further information. This webpage depicts what the climate and weather patterns might be like if the AMOC collapses, an event it suggests could happen by 2050 if global temperatures rise by 2+C – https://amocscenarios.org/?lat=45&lon=-5&model=cc_RCP45&is_amoc_on=false&is_delta=false&metric=warm_days

Lent – choice & tipping points

24th February 2024

The desert and the parched land will be glad; the wilderness will rejoice and blossom like the crocus Isaiah 35:1

You Lord, are the source of all good things:

We praise you.

You call us to tend and care for your creation:

May we strive to do your will.

You have made us as brothers and sisters with all that lives:

May we live together in peace.

A reading from Deuteronomy 30:16a, 19 I command you this day to love the Lord your God and to keep his commands, decrees, and regulations by walking in his ways…. Today I have given you the choice between life and death, between blessings and curses. Now I call on heaven and earth to witness the choice you make. Oh, that you would choose life, so that you and your descendants might live!

A litany of tipping points

Adam, Eve and the fruit that was good to eat:

Eat and be self-determined?

Not eat and be God-determined?

– A tipping point.

Moses, Pharaoh and a river of blood:

Let the people, these troublemakers go?

Follow the call of this troublemaking God?

– a tipping point.

A people, a rule of life, and a golden calf:

Accept the short-termism of humanity and give up;
Plead God for mercy and start over afresh?

– a tipping point.

Exile, return and rebuild a new future:

Same old temple, same old rule-bound exclusivity;

New heart, new faith, an openness to others?

– a tipping point?

Repent, good news, healings and miracles:

A charade, a charlatan, a feel good non entity;

Revelation, reformation, real life born afresh?

– a tipping point?

Rebellion, deception, execution:

Confrontation, subjugation, might is right;

Confraternity, transformation, God is right?

– a tipping point?

Empty tomb, close encounters and reunions:

Disbelief, cynicism and a hasty coverup;

Joy, mystery and real life resurrection?

– a tipping point?

Tipping points are many and varied.

Some good, some bad.

Help us life, affirming God,

to see the tipping points we face,

to see the hazards to avoid,

the new routes to ride.

Help us, life affirming God,

to heed the words of your present day prophets,

the pleas of your children across the globe,

and the anguished cries of the earth.

Inspire our hearts and empower our actions,

that we may be a tipping point for good.

Help us, life affirming God,

to see again in the life and resurrection of Jesus,

the example we should follow,

to know once more that Christ’s gospel

will continue to transform the world.

Amen.

Counting on … day 51

22nd February 2024

Tipping points – “In climate science, a tipping point is a critical threshold that, when crossed, leads to large, accelerating and often irreversible changes in the climate system.” https://en.wikipedia.org/wiki/Tipping_points_in_the_climate_system

Likely tipping points if we reach 1.5c of warming include the loss of boreal permafrost in the artic regions. This would result in the release of large amounts of methane rapidly increasing the rate of global warming.
Another potential tipping point would be the die-out of mangroves and seagrass meadows in the tropics, reducing how much carbon dioxide is absorbed by the oceans and so fuelling further global warming.

Tipping points accelerate global warming.

Further reading – https://www.theguardian.com/environment/2023/dec/06/earth-on-verge-of-five-catastrophic-tipping-points-scientists-warn?CMP=Share_iOSApp_Other

The Green Tau Issue 5

Counting on … day 1.125

13th July 2023

Sometimes change happens at speed. A tipping point is reached and everything accelerates. On Monday I reported on being at York where General Synod has received a report from their national investment body explaining their decision to divest from fossil fuels. Over the weekend the Diocese of York announced that it too had decided to divest from fossil fuels. Yesterday the Diocese of Southwark decided to follow the same course of action.

Can we ensure this rapid and increasing desire to take action to safeguard the environment from the worsening effects of the climate crisis will continue?
We can pray. We can talk about the issue and continue to raise awareness about the extent and urgency of the crisis. We can be motivated to make changes in our own lifestyles.