Biophysical processes are not always gradual and linear, but sometimes lead to a sudden change of state

One of the greatest challenges in addressing the climate crisis is the ability for humans to perceive change over long time periods.

Another is human propensity to understand processes beyond direct cause and effect.

You do something, you get a response. It is gradual, immediate and predictable.

But there’s another way.

Sometimes processes reach a point where they abruptly turn into something else.

And this applies to the climate system, but it can also apply in everyday life.

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The hydraulic press presses down on the ball. For a time, the pressure (induced change) is constant as is the response. Abruptly, the ball changes state and explodes.

A toxic substance is poured into a clean lake. The pouring of the substance is constant and so is the response. Abruptly, the toxic substance comes to a point where it kills animal and plant life and the lake is no longer safe for use.

You drink 8 beers every day. The drinking is constant so is the response. Abruptly, you get ill more frequently and more serious life-threatening diseases develop.

You treat your spouse terribly. They put up with it for a while. Abruptly, they leave the relationship.

The same can be said about natural ecosystems and the climate. Pressures that could ‘tip‘ it past a threshold and into a new state, with no return.

We have also observed global tipping points in the historical palaeo-climatic record, including sudden shifts into ice ages.

Scientists believe there could be at least 9 tipping points.

What is itWhat does it mean?
1. Greenland ice sheet disintegrates7 metres of sea level rise
2. Permafrost lossSharp increase in emissions which are otherwise trapped under frozen carbon-rich soil
3. Boreal forest shiftStored carbon would be lost
4. Atlantic meridional
overturning circulation (AMOC)
Ocean circulation disrupted. Western Europe and North America several degrees cooler.
5. Amazon rainforest diebackBiodiversity loss and decreased rainfall
6. West African monsoon shiftAgriculture disrupted and a change in ecosystem
7. Indian monsoon shift Agriculture disrupted and more extreme rainfall
8. West Antarctic ice
sheet disintegration
3 metres of sea level rise
9. Coral reef die-offEcosystem change and fisheries loss

Around 20 years ago it was believed these impacts would be unlocked at around 5°C of warming. It is now understood that some of these points may be tipped at between 1 and 2°C of warming.

Some may already be ‘tipping’, with the AMOC (point 4) having weakened by some 15 per cent.

While some of these thresholds are starting to be crossed, time is still on humanity’s side and efforts can prevent further damage. For example, the melting of the Greenland ice sheet (point 1) could be around ten times faster at 2°C of warming compared to 1.5°C.

Evidence is mounting that these events may be interconnected. For example, Arctic sea ice loss and Greenland melting drives fresh water into the ocean. This could affect the slowdown of the AMOC, which could destabilise the West African monsoon and dry the Amazon and heat the Southern Ocean, which could speed up Arctic ice loss.

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