- Is one degree of warming, really that big of a deal?

How about two?

Could 1 1/2 or two degrees of warming from pre-industrial levels mean doomsday or game over?

Seems kind of extreme, but we know that the earth will look different as the climate warms because we can already see some of it happening around us.

And there are some pretty amazing models that predict what the world would look like with changes set in motion by just a bit more warming.

So who's gonna be affected?

Where will we feel the effects first?

And how can such a small change matter in such a big way?

The answer lies in understanding tipping points, but when will we reach them?

- In the early 2000s, the kind of general consensus would've been maybe we're at risk of tipping points at, say four degrees C of global warming, where now we just publishing a study which essentially says exceeding 1 1/2 degrees Centigrade of global warming about pre-industrial risks, multiple climate tipping points.

- And that's very close to our current level of about 1.1 degrees of warming.

So let's find out what the world would look like if we hit six of the 15 most pressing tipping points identified by the International Panel on Climate Change.

First, we'll explain how changes that could be set in motion very soon would fundamentally change our world.

And stay with us until the end when we see just what the earth would look like if they tip.

(gentle music) Imagine a chair sitting flat on the ground.

Adding a small tilt won't change much, but if our director is leaning back in the chair, precariously balanced, and adds just a tiny degree more lean, the chair reaches its tipping point and suddenly falls until it finds its next stable state.

And this is essentially what's happening to our planet's climate.

Many of our planets systems getting precariously close to sudden potentially irreversible change.

We'll begin our journey all the way up in the Arctic, which is warming about two to three times faster than the rest of the planet.

This is because as global warming melts the reflective white sea ice, more and more of the dark blue ocean below is revealed, which absorbs energy from the sun further warming the region.

That gets us to our first tipping point.

(suspenseful music) - We're seeing accelerating melt of the Greenland ice sheet 'cause of that extra Arctic heating.

- It's not just darker water absorbing warmth from the sun.

As Greenland's ice melts, it exposes land which heats up faster than the more reflective ice in water around it, speeding up the melt by 60%, according to one recent study.

Some of this is already happening.

- We're confident that the Greenland ice sheet can have a tipping point of where the melt and shrinkage of the ice sheet becomes irreversible.

That could be close.

- Like, very close.

Tim recently published a study saying that the irreversible threshold could be just 1.5 degrees.

- Certainly the ice melts and shrinkage is accelerating, and has been for several decades now.

And then the melt water that's pouring off Greenland either side into the North Atlantic Ocean that poses a risk for what's called the great overturning circulation of the Atlantic Ocean.

(suspenseful music) - This is commonly referred to as the AMOC.

It's essentially a giant flow of water that acts like a global conveyor belt, bringing heat from the Southern Hemisphere, all the way up north to Greenland.

- Under normal service, the water gets cold enough, and salty enough, and dense enough to fall from the very top of the ocean all the way to the bottom in a process we call deep convection in the seas either side of Greenland.

But if you add fresh water pouring off the Greenland ice sheet, and you make the surface waters fresher, less dense, less prone to sinking to the bottom of the ocean.

And this is certainly a factor contributing to some observed weakening of this great overturning of the Atlantic Ocean.

- Some calculations show that the AMOC has already weakened by around 15% in the last 50 years and scientists fear it could eventually slow to a halt, which would have extreme impacts on global climate as a whole.

But even a partial collapse could plunge Europe into a mini ice age, and raise sea levels along the Northeast seaboard of North America by 20 or 30 centimeters.

And models show that the tropical rain band that surrounds the earth would likely shift further south.

(suspenseful music) - Well, that means disrupting monsoon systems around the tropics, kinda near the Atlantic and west Africa on one side and South America, the Amazon region on the other, but also around the planet in India.

- Farmers around the world count on these reliable rain cycles each year.

Changing their timing, location, or strength would disrupt the livelihoods of over a billion people and complicate global food supplies as agriculture has to relocate and productivity is decreased.

This could cause a large climate migration and weaken the food supply of over a billion people.

- Disrupting the rainfall regime and the monsoon over North and South America could be a big risk factor for the Amazon Rainforest, which is definitely at risk of already observed increasing length and severity of the dry season in what otherwise we think of as the perennially rainy rain forest.

(upbeat music) - In fact, the Amazon experienced three one in a hundred year droughts between 2010 and 2020.

These severe droughts contributed to massive diebacks.

And for the first time in the forest observed history, a large portion of it flipped from being a carbon sink to a net carbon source of greenhouse gas.

- So if this monsoon disruption amounts to further intensification of the dry season, that's the thing that could risk a more widespread dieback in the Amazon Forest, that then becomes self-propelling because the Amazon recycles its own rainfall back to the atmosphere.. And you take the trees away and you reduce the recycling, that tends to take more trees away and so on and so forth.

Well, we don't want that to happen for various reasons 'cause we don't wanna lose perhaps the greatest harbor of diverse life under Earth's land surface.

- Okay, that's not great, but now let's head back to the ocean and continue south.

- If the Atlantic overturning is weakening, leaving heat behind in the Southern Ocean and heating up of the Southern Ocean is the biggest threat factor for the Antarctic ice sheets.

(upbeat music) - And as we've covered in a previous episode, we know that the West Antarctic Ice Sheet is already the stabilizing and could be close to a tipping point without added warming of a weakened AMOC.

- And yeah, if you heat the ocean up, that's the big threat factor to further accelerating the loss of that ice sheet, but also a threat to the bigger East Antarctic Ice Sheet.

You start to trigger a retreat of the glaciers that causes the glaciers to flow out faster, so it becomes self-propelling.

So that's a lot of bad news, isn't it?

- Well, yes Tim.

Yes, it is.

So what's next?

- The permafrost is soaring at an accelerating rate.

Not least because the whole Arctic is warming at an accelerating rate, and the permafrost is important because it's a really big frozen store of carbon.

- Really quickly, permafrost is land that's frozen year round, and has been for a long time.

When it's frozen, there's no tiny bugs to eat the organic matter it contains.

So the massive stores of carbon are safe.

- As you start to thaw it, well, you start to release that carbon because bugs are basically going to work.

They might be the kind of bugs that turn some of that carbon into methane, which is a far more potent greenhouse gas than carbon dioxide.

That meanwhile other bugs are turning it straight to carbon dioxide, both of those things are being added to the atmosphere, adding to warming.

But on top of that, when bugs eat for carbon that's coming out of the deep freeze, they release heat, just like tummies release heat when we eat food.

That releasing of heat in that permafrost column can thaw more of the permafrost giving them even more food to eat to generate even more heat, to thaw even more permafrost.

And that means a true tipping point of sort of self-propelling breakdown.

- And to put that into context, we're talking about hundreds of billions of tons of carbon dioxide and methane that could be released from the permafrost, which would add measurably to global warming.

- By 0.1, 2, 3 two of a degree C and adding to the overall risk and adding to the likelihood of tipping some of those other systems, if they haven't gone already.

- We're clearly talking about a very different future of the world here, and there's one tipping point that has likely already been reached.

(suspenseful music) There's still lots of living coral, but it's being bleached so quickly by hot ocean water that it may never exist in the way that it did just a decade ago.

So I asked Baratunde Thurston from "American Outdoors: Understory," what swimming over a reef is like and what the loss of coral reefs means to him.

- I felt like I was flying across this underwater mountain range, but unlike any mountains I'd ever seen.

It was like mountains made of hyper colors and there were fish flying around too.

And they were saying what's up, and I was saying what's up.

And the idea that they wouldn't have a home, that all of that life would be dead, that all those colors would be bleached out, I'm really, really sad about the prospect that we will lose a piece of ourselves when we lose these coral reefs.

- It takes a while for the consequences of passing a tipping point to fully unfold.

It can happen a lot quicker for coral reefs as we've seen with iconic bleaching events across the Great Barrier Reef and the like.

- So what will the earth actually look like if we reach these tipping points?

Well, it's pretty dramatic.

With melting eyes from the Antarctic and Greenland ice sheets, Tim says we're already committed to 10 meters of sea level rise, which will essentially redraw the coastlines of the world and displace about a billion people.

The AMOC collapse is fascinating.

A total collapse could actually mean something of a mini ice age in parts of Europe, as well as significant sea level rise along the Northern seaboard of the U.S. Amazon dieback would turn much of Brazil from a rainforest into a very different ecosystem, potentially grassland or even drier.

And while Greenland ice melt would cause massive sea level rise globally, locally, there will be more room for agriculture and people as the ice exposes more land.

As melting continues, places like Siberia and Northern North America that currently have very shallow permafrost could see larger and more dense forests in the long run.

But in the meantime, we'll have some funny-looking drunken forests and of course, a lot of greenhouse gases - This has got profound implications for the kind of every other living thing and the future trajectory of evolution.

So it's a hell of a legacy for us to be leaving.

- But this isn't written in stone, and there's still time to stave off the worst-case scenario.

Still we know some adaption will have to happen and Tim has an idea for mitigating the impacts of those tipping points that we just can't avoid.

- We know now, even just directly from observational data, we can see systems losing stability before they hit a tipping point.

So if we have an effective tipping point early warning system that's telling us about some of the most impactful biggest risks that are coming, in simple terms, forewarned is forearmed.

I mean, we can use our resources wisely to reduce the damage even for the unavoidable stuff.

- There are examples already in use for earthquakes, tornadoes, hurricanes, and even wildfires, but does a planet scale warning system seem possible?

I'd love to hear from you.

What would it take for us to make the changes needed to stop warming at 1.5 or two degrees?

And remember that even though these are major scary changes we're talking about, there's still so much beauty in the world to enjoy.

Just think of all the wonderful corals that are still thriving.

(gentle music)