The Tipping Points of Climate Change — and Where We Stand | Johan Rockström | TED

We Earth system scientists and climate scientists

are getting seriously nervous.

The planet is changing faster than we have expected.

We are, despite years of raising the alarm,

now seeing that the planet is actually in a situation

where we underestimated risks.

Abrupt changes are occurring in a way

that is way beyond the realistic expectations in science.

Fifteen years back, I introduced the planetary boundary framework,

the scientific framework with the nine Earth system processes

that determines the stability, the resilience and the life support

on planet Earth.

Ten years back, the world signed the Paris Climate Agreement.

Almost five years back, we entered the decisive decade

where our choices will determine the future

for all generations on planet Earth.

Where are we on this journey,

halfway into this decade?

I will give you a scientific state of the planet report,

the most objective assessment that science can give today.

And it starts here.

We've reached 1.2 degree Celsius of global mean surface temperature rise,

the warmest temperature on Earth

over the past 100,000 years.

We have just scratched on 1.5 degree Celsius

as an annual mean in 2023.

But what worries us most is this:

we are starting to see an acceleration of warming

over the past 50 years.

0.18 degrees Celsius per decade from 1970 to 2010.

But then from 2014 onwards,

it abruptly jumps up to 0.26 per decade.

And if we follow this path,

we will crash through two degrees Celsius within 20 years

and hit three degrees Celsius by the year 2100,

a disastrous outcome, caused by us humans.

But it's not only carbon dioxide.

Any parameter that matters for human well-being and our economies

look the same.

Here you have it, linear change up until the 1950s,

we go into the great acceleration.

And this is what we're seeing across overconsumption of fresh water,

the sixth mass extinction of species,

over-putrefying our freshwater systems with nitrogen and phosphorus,

all of it undermining the stability of the planet.

As if this was not enough,

we are seeing that this is now causing impacts across the entire economy.

We're seeing bigger and bigger invoices

being sent by the Earth system onto societies across the entire world,

in droughts, floods,

heat waves, disease patterns,

human-reinforced storms,

scientifically attributed to human-caused climate change.

Forty degrees Celsius of life-threatening heat

across all continents, occurring in 2023.

Fifty-two degrees Celsius hitting the over 1,000

who lost their lives at the Hajj pilgrimage

in June in Mecca.

Three times higher climate change risks

now attributed to our cause of climate change.

2023, up to 12,000 deaths,

200 billion US dollars of cost,

just in the US, up to 100 billion US dollars.

This is seriously causing economic costs.

We have scientifically, in the past,

shown that this could cost a few percent of global GDP

of the climate impacts caused by us.

I can tell you that the latest scientific assessment

is what you see on the screen here.

An 18-percent loss of GDP by 2050

if we now follow the current path.

This is equivalent to 38 trillion US dollars of loss

per year in 2050.

It's starting to hurt.

Both in human social costs and an economic cost.

And this is happening at 1.2 degrees Celsius

of global mean surface temperature rise.

And we're following a pathway that takes us to 2.7 degrees Celsius

in only 70 years.

And we've had a 10,000-year period where our civilizations have developed,

where we've had an enormous privilege

of a planet at 14 degrees Celsius,

plus or minus 0.5 degrees Celsius.

That's the Holocene since we left the last ice age.

And if you look three million years back,

we never exceeded two degrees Celsius.

That's the warmest temperature on Earth during the entire Quaternary.

The coldest point, minus five degrees Celsius, Ice Age.

I call this the “corridor of life.”

Is it surprising that we scientists are getting really, really nervous?

But it's more.

It's so much more than this.

The first issue is buffering capacity.

The second is the risk of crossing tipping points,

and both are moving in the wrong direction.

Buffering capacity is the Earth system's ability to dampen shocks and stress.

Like, for example, soaking up greenhouse gases

in intact nature on land and in the ocean.

And so far, Mother Earth has been so forgiving.

Here we have the evidence.

What you see here is the hockey stick of fossil fuel burning in red

and deforestation in yellow.

Is it this tremendous climate forcing

that has caused the 1.2-degree Celsius climate crisis so far?

The answer is no.

Fifty-three percent of the carbon dioxide

from fossil fuel burning and land system change

has been soaked up

by intact nature on land and in the ocean.

It’s only the blue sliver you see here,

which remains in the atmosphere, causing the climate crisis so far.

The problem is

we have more and more scientific evidence of cracks in this system.

Let's start on land.

Land absorbs 31 percent of the carbon dioxide

from our greenhouse gas emissions.

We have more and more scientific evidence across so much research

that the boreal forest in Canada,

or the temperate mixed forest in Germany and Russia

are starting to lose their carbon uptake capacity.

Did you know that the latest science shows

that the part of the Amazon rain forest,

planet Earth's richest biome on terrestrial land,

has already tipped over and is no longer a carbon sink?

It is today a carbon source.

It's no longer helping us.

But as if that was not enough,

what really worries us today is the ocean.

The ocean absorbs 90 percent of the heat

caused by human-induced climate change.

This is well understood,

but what really worries us is what you see here.

This is the latest data on sea surface temperature across the ocean.

What you see here is from 1980 until today,

how gradually the ocean surface just gets warmer and warmer.

It's actually warming all the way down to 2,000 meters depth.

This is well understood in science.

It's a deep concern.

It's well represented in the climate models,

we understand it.

Then suddenly in 2023, something happens.

Temperatures just go completely off the charts.

0.4 degrees Celsius outside of the warmest temperature

in previous years.

What's happening?

We admittedly must be honest here,

we do not know.

El Niño is certainly partly to blame but cannot explain it all.

2024, it just continues.

What is happening?

We do not know.

But the candidate number one

is the energy imbalance caused by us humans.

In one year alone,

the heat equivalent to 300 times global electricity use

is absorbed in the Earth's system.

Is it what we see on the screen here,

an ocean that is starting to lose resilience?

An ocean that is at risk of releasing heat to the atmosphere

and self-amplifying warming?

We do not know.

But one thing is for certain, the ocean is sounding the alarm.

Reasons for concern, yes.

We are now at a point where we are forced to ask

the following question:

Are we at risk of pushing the planet out of the basin of attraction,

the stability of the planet,

where we’ve been since we left the last Ice Age,

the extraordinarily stable Holocene state?

And if we pushed ourselves outside,

drifting away unstoppably towards a hothouse Earth

where we get self-amplified warming

and losing life support on Earth.

What could take us there?

Well, we know it.

It is if we cross tipping points,

big systems like the Greenland ice sheet,

the overturning of heat in the North Atlantic,

the coral reef systems,

the Amazon rainforest are tipping element systems.

Push them too far, and they will flip over from a desired state that helps us

to a state that will self-amplify in the wrong direction,

going from cooling and dampening to self-amplifying and warming.

A rainforest tips over to a Savannah state.

Now we have now mapped the 16 tipping element systems,

which are now scientifically cataloged, that regulate the climate system.

These 16, and you see the five in the ground zero on planet Earth,

in the Arctic,

are connected via cascades through the ocean,

particularly via the AMOC,

the Atlantic overturning of heat in the ocean,

all the way down to Antarctica.

These are big biophysical systems that we all depend on,

global commons for the stability of the planet.

The question is, at what temperatures are they at risk of tipping

from helping us to becoming self-amplifying foes?

Well, for the first time,

we have an attempt to answer that question.

What you see here are the 16 tipping element systems on the y axis,

and in red you see the uncertainty range,

the best estimates in science,

darker the red, the higher the risk of tipping,

it's the temperature levels

at which they're likely to cross the threshold.

The average temperature at which they are likely to tip

is the yellow circle lines you see here.

What this tells us is the following.

Five of these 16 are likely to cross the tipping points

already at 1.5 degrees Celsius.

The Greenland ice sheet, the West Antarctic ice sheet,

abrupt thawing of permafrost,

losing all tropical coral reef systems

and collapse of the Barents Sea ice.

And just the two ice sheets

hold ten-meter sea level rise,

which would be unstoppable on the long term.

Now sure, there is scientific uncertainty here,

as you see from these graphs,

but there's one red thread in science for humanity in the scientific message.

And it's this: the more we understand of the Earth's system,

the higher is the risk.

And here is the proof.

This is five IPCC assessments

the Intergovernmental Panel on Climate Change,

30 years of scientific advancements.

Here again you see risk assessment,

darker the red, higher the likelihood of causing irreversible change

in the climate system.

Thirty years back, the risk was put at five degrees Celsius

of tipping

and coming down to current state of science,

the risk is set at 1.5 to two degrees Celsius.

We are in the midst of a danger zone today.

But it can be even worse than that.

Let's go to the Amazon basin, again,

the richest terrestrial ecosystem on land,

climate science estimates the risk

of the Amazon rainforest tipping over irreversibly to a savanna

at three to five degrees

of global mean surface temperature rise.

A really high temperature,

unlikely even to be met over the next 70 years.

But if we lose forest cover,

the risk is that the system can tip already at 1.5 to two degrees Celsius

if we lose more than 20 to 25 percent of forest cover.

So that's a very dangerous combination.

Where are we today?

We are at 1.2 degrees Celsius of global mean surface temperature rise

and 17 percent of deforestation.

We are very close to a tipping point in the Amazon rainforest.

Very close.

What shall we do to avoid these unmanageable outcomes?

Well, the IPCC is clear on the pathway.

To stay under 1.5 degrees Celsius,

to avoid crossing tipping points,

we need to operate, to navigate within the global carbon budget

that gives us a chance of holding 1.5.

What remains for us is only 200 billion tons of carbon dioxide

that we can continue emitting

to have a 50 percent chance of holding 1.5.

We emit today 40 billion tons of carbon dioxide per year,

giving us five years at current rates of emission

before we've consumed the budget.

We are seriously running out of time.

And the pathway for a safe landing is also well studied and understood.

You have it here.

Bend the curve of emissions immediately

and follow a path where we reduce emissions

by at least seven percent per year for a safe landing

and a net zero world economy by 2050.

But it's more than that.

We also know that even if we succeed with this,

we have already loaded the atmosphere with so much greenhouse gases,

with so much climate forcing,

that we inevitably face a period of overshoot.

We must now be prepared for a very likely breaching

of the 1.5-degree-Celsius planetary boundary on climate

somewhere between 2030 and 2035.

In five to 10 year's time.

And then have, at best, a 30-40 year period of overshoot

before we can come back to 1.5 by the end of this century.

We would exceed with 0.1 to 0.3 degrees Celsius

the 1.5 limit,

meaning up to 1.8 degrees Celsius.

What does this tell us?

Well, I can tell you there are two main messages.

Message one:

Buckle up.

We know for certain, 100 percent certainty,

that this means more droughts, more floods,

more heat waves, more human-reinforced storms,

more disease during one generation's time.

2023, the warmest year on record,

will be looked back upon as a mild year.

Message two.

Why would the planet come back to 1.5 after overshoot?

Well, the answer is very simple.

The health of the planet must be kept intact.

We must continue having a planet

that can absorb 50 percent of the carbon dioxide.

We must have a planet that crosses no tipping points.

We must have a planet that remains healthy

and keeping heat intact in the ocean.

That is why we need planetary boundaries.

The planetary boundary framework

that defines the nine Earth system processes

that regulates the stability and resilience of the entire planet:

climate, biodiversity, nitrogen, phosphorus, land, fresh water,

air pollutants and chemicals.

That is the challenge.

To summarize that,

there is no 1.5 degrees Celsius delivery

on the Paris Agreement by only phasing out fossil fuels.

We also need to come back into the safe operating space

of the nature-based biodiversity,

all the planetary boundaries of nature.

This means that science is clear.

The window is rapidly closing,

but there is still some light in the window.

We actually have evidence that we've reached a pivotal point,

not only in terms of risk,

but also in terms of opportunity to transform the world

towards a safe and just future for humanity.

Linear change is no longer an option.

The only option is exponential change.

We know that the only currency that matters is speed and scale.

We also need to become stewards of the entire planet.

We need to now recognize, from local to global level,

that we're all so intertwined that we must govern the entire planet.

I know, that is very daunting,

but what choice do we have

when on the line is the future of our children

on planet Earth?

And we have the solutions.

We know that solving the planet crisis is not utopia.

It's not fantasy.

We have the solutions for a secure, stable future for humanity.

What are those transformations?

Well, we know them.

It's a rapid transition away from fossil fuels.

It is a transition towards circular business models.

It is transitioning towards healthy diets from sustainable food systems.

And it's not only halting loss of nature,

it's also scaling the regeneration and restoration of marine systems, soils,

forests and wetlands.

We have solutions for all of these.

Just take green energy,

which today is cheaper than fossil fuel-based energy.

It's our choice that we're facing today.

Now I was nervous already in 2020

when we entered this decisive decade

and had to cut global emissions by half by 2030.

Halfway into this decade,

the road is steeper than ever.

It's steeper than ever.

This is what really, really concerns us.

That we have a situation where we now need to move so fast.

And I've been standing on stages like this so many times,

sharing the dire scientific diagnostic.

But still, I just told you

that I do conclude that there is still some window open.

There is a light in the tunnel.

And you may ask, what is it that makes me able to continue

to be a realistic optimist in this situation?

The most dire situation, I must admit, in my whole professional life.

Well, actually, I promise this is an honest statement.

there are so many positive items as well.

The most important one in my mind

is that we have ample evidence

that citizens across the world, a majority of them,

care about nature and climate.

They trust climate science,

they're concerned about climate change,

and they want solutions.

And the second key factor

is that we have so much evidence today

that the solutions are not only available,

but if we implement them,

we get a more healthy, stable,

secure future with the jobs and the economies

that can compete and provide livelihoods into the future.

This means, dear friends,

that solving the planetary crisis is not only necessary,

it is possible,

and we all win if we succeed.

Thank you very much.

(Applause)