weekly podcast from the BBC World Service.

We speak to experts, activists, businesses and reporters from all over the world about the biggest issues when to comes to climate change.

It's always interesting.

Really, really, really looks like a James Bond film. I'm slightly nervous. We're standing on top

of the reactor. Atoms are being split, minds are being blown.

And sometimes slightly unexpected!

Ah! Are you OK? It's gone now I'm alright. I just throw it back into the water. That was some kind of sea creature

came for you? Yeah.

In this special episode I'm joined by experts and friends of our show to answer one of the most commonly searched

questions: What is climate change?

OK we've got Dr Rose Mutiso - Rose what do you do? I'm the research director at the Energy for Growth Hub. I work on

energy and climate, technology and policy in developing countries.

Dr Zeke Hausfather - what do you do? I'm a research scientist at Berkeley

Earth which helps produce one of the global temperature records.

Adam - complete the trio. Adam Levy. My surname is pronounced Levy, like, leave me alone. So I suppose

a climate scientist and YouTuber.

Thanks guys. A lot of people are too afraid to ask the really simple questions when it comes to big

news stories as they don't want to look stupid - but not me! Think of me as an

inquisitive five year old – I'm just going to keep asking 'Why why why?' on your behalf.

But first a what.... What is climate change? Zeke what does that term actually mean?

So when we talk about climate change, what we're really talking about is heat

being added to the Earth system. So as humans burn fossil fuels, we dig up

from underground, or as we cut down forests that have been standing for

hundreds of thousands of years, we are putting carbon dioxide into

the atmosphere. Carbon dioxide is a greenhouse gas,

and the more greenhouse gas you have in the atmosphere the more of the sun's heat

gets trapped in the atmosphere and the warmer the surface gets and that's why

it's called a greenhouse effect.

Wait a minute! I said simple. Adam, what are these greenhouse gases people keep talking about?

Greenhouse gases on their own are actually great, they exist naturally in the atmosphere. And if they didn't,

the world would be way too cold for comfort. So greenhouse gases on their own good,

they work like a nice, warm blanket, keeping the Earth from the cold space

around us helping insulate the planet. The problem is that we're adding to them hugely.

So it doesn't take a doctorate in climate science to understand that

if something insulates the planet and you add a whole bunch

more of it to the atmosphere, then you're going to have more of that insulation effect

and things are going to start to heat up. And that's exactly what we're seeing.

There's been so much coverage of climate change and this global warming

you'd think this is something we'd have changed by now. Another basic question.

Why haven't we just stopped adding to this 'nice warm blanket?'

All of the systems that underpin our lives, so how we produce food to eat, how we

create energy to heat our homes, how we create electricity to power our devices and our

machines, how we fuel our cars. All of these processes require energy inputs.

I focus on the energy sector, my energy sector is the biggest part of the problems.

How we produce and use energy, really a massive chunk of it. And so

for the most part, historically, we burn fossil fuels to produce energy,

whether it's heat, whether it's electricity, whether it's fuel, so think of your petrol or your jet fuel.

Fossil fuels are essentially remains from plants and animals from millions of years ago,

under heat and pressure and time create really efficient sources of energy. And so we

burn them. And we can create heat and electricity and everything. But then we

also produce carbon dioxide as a side effect.

OK some people will be thinking I like hot weather, what is so bad about the world heating up?

So the world getting hotter will have some very direct effects on places which are

already pretty hot, you know, if you're in a particularly hot city, and that

suddenly gets a chunk hotter, that's going to make it a lot harder to live in that city.

But beyond that, around the world, we're seeing a whole host of

really scary impacts of climate change already happening today. For example,

climate change is turbocharging all sorts of extreme weather events,

whether that's things like heatwaves, floods, droughts, wildfires.

Someone here was saying it was hotter here than in Africa.

Also the heat comes in the wake of Covid too, so you have Covid, then you have heat, it's almost biblical.

The effects that Adam mentioned are terrible. Floods, droughts and wildfires. But it's not

clear to me how the Earth warming would actually create them. It's 'why' time again...

Explain to me how the world getting warmer causes floods. That seems

to be the opposite of what I would have thought would happen.

So a hotter atmosphere works like a more effective sponge, it can hold more water.

And that means when you have really heavy downpour events, there's actually just

more water there in the atmosphere waiting to be rained out. And so when it rains, it pours.

On The Climate Question we have seen first-hand the effects that these impacts can have - we go around the world

to speak with people on the front line of climate change.

Floods have destroyed much of my country, Pakistan. The waters have killed some 1500 people, and displaced millions.

So sea levels rising, there's actually a couple different

factors driven by climate change that cause that. One very simple one that

people don't often appreciate is that as the oceans warm

warm water takes up more space than cold water. And so you get this thing called thermal expansion,

where the warming of the oceans literally causes the water to take up

more space and the sea levels rise because of that. But in addition to that

warmer temperatures cause ice sheets to melt, and not just melt from the top down, but

also to flow faster into the oceans. And we've already seen a huge increase in the

rate of ice loss from Greenland in particular, but also parts of Antarctica

over the last few decades. And so that's been increasingly driving the sea level rise

that we've been seeing globally.

It's not just the wet stuff we also go from floods to fire.

Some parts of the world are also experiencing more drought as more water gets carried away from those areas.

And so if you have hotter and drier vegetation, if a fire starts it's easier for that fire to find enough

fuel to grow bigger and to spread much more rapidly and much more widely.

Some people will be listening and thinking that all sounds terrible but it hasn't hit them yet.

Life is busy.

There's constantly things on the news to be worried about. But climate change will affect all of us...

Europe, for example, a lot of regions around the Mediterranean could potentially become

too hot for people to live in the way that they currently live in these regions.

But heat waves don't just affect regions we currently associate as hot.

Extreme heat is already affecting different parts of the world, the world over today.

And in fact, heat waves in the last couple of years in Western Europe

have claimed many thousands of lives. And these are relatively rich, relatively

cool parts of the world. You then extrapolate that to parts of the world,

which are really hot already, for example, certain Middle Eastern countries,

then you're risking these countries simply becoming too hot for habitation

in coming years. Sea level rise will affect coastal regions, but particularly

vulnerable to sea level rise are countries which we call low-lying island nations,

which are islands which aren't that high above sea level.

And if we can't control climate change, we're looking at these nations effectively

ceasing to exist, the people who live in them needing to relocate their way of

life being extinguished by climate change.

Modern life depends on energy – electricity or fuel. As Rose mentioned, the problem is the system that underpins

nearly all of our life. So do we just stop...you know doing everything?

Obviously, we need to continue to, you know, run our factories and power transportation

systems that can get us from A to B, you know, just because there's climate change

doesn't mean that we stopped needing to eat or to work or to create things that

underpin our modern existence, right. And so the opportunity is that they're kind of

cleaner more efficient, better ways to create energy, right. And so for example,

in electricity sector, so instead of the traditional power plant that, say uses

coal, which is a very kind of, extremely polluting fuel, burns coal to

create electricity, we can make electricity from the sun, using solar panels.

Or we can make electricity with wind turbines right.

But the pace of technological change is really, really exciting. Similarly, for transportation, so

instead of, you know, putting petrol in your cars, now we have electric vehicles

and there's a lot of innovation around that. The way we're designing our cities

to reduce the need for driving, folks are biking, walking, public transit

they're just all of these great approaches that we're taking to try and reduce our reliance on fossil fuels.

Lots of changes are already happening and we'll each have seen technology improving in our own lives,

so why are some people saying actually it's too late for solar panels or for electric vehicles. That the world will warm to a point where we can't live in it.

But is that right? Is it too late?

Climate change isn't like that. Climate change, I always say, is more like getting punched in the face.

It doesn't matter how long you've been being punched in the face, you still want that punching to

stop. And so say you set a limit for okay, I only want to be punched 10 times

anything more than that would be a catastrophe. Okay, now you've been punched

11 times. Well, 12 punches are still worse than 11 and 13 is still worse than 12.

And so throwing our hands up and then saying 'Oh, it's too late now'.

That's just not good enough. There's still so much we can do to stop punching ourselves in the face.

We are ultimately in control of our climate destiny, we can decide if we're

going to have 1.5 degrees warming this century, or five degrees warming this century,

or somewhere in between. And one thing that the climate science is pretty clear

on is that every 10th of a degree matters. There's no threshold where

we go from everything being fine to climate change spiralling out of control and

the end of the world. It's not like 1.4 degrees centigrade globally is great and 1.6 degrees

is an apocalyptic hellscape. Rather it gets progressively worse

the more warming we have. And in many ways, the more warming we get, the more worse it gets.

And so if we do end up stuck in a world of 1.8 degrees, or even two degrees, it becomes all

the more important not end up at 2.1 degrees or 2.5 degrees.

There's no point at which it's too late.

For me, after hearing all this, there's just one question that I have – what can I do to make a difference?

Go and vote. Get engaged in your politics at the

local level of the national level, get involved.

And I know it seems almost like a silly thing to say. But I cannot emphasise how

important is to vote because the people that you vote in - policymakers,

legislators - they have so much sway over how we tackle climate change.

So all of this stuff is really decided at the level of policy and behind policy

are politicians and I know they're not always our favourite people, but that's on us

because we pick them. And so I just say, always get engaged. You know, do

your civic duty, read up on the candidates, make sure that people that are getting

voted into power are people who have, you know, practical solutions, understand the issues.

And that's actually a question we get asked a lot on the podcast

and you can hear an entire episode on changes you can make to help – find it wherever

you get your podcasts. Adam, please tell me things are changing for the better or there's at least some hope!

I would say they're two really huge changes since I started working on climate change

around 12 years ago. The first is back then when I started

renewables were still pretty expensive. And so the big question was, well we

know we need to make this shift, how can we? How can we get people to spend more money to make

this electricity? Well, that has been turned absolutely on its head in the

last years, as solar and wind have become just breathtakingly cheap.

On top of that, the big, big change that I've seen is that when I started working on climate

change, people weren't really talking about it. And it often felt like us

climate scientists was screaming into a void.

Well, it's not like that anymore. People are talking about climate change more and more with each other.

People are acting on climate change in their personal lives and pushing for climate

action from governments and companies. And climate change is now ranked world over

as one of people's top concerns. And so the fact that we're all now taking

this more seriously, talking about it more and acting on it more, gives me a

huge amount more hope than I had a few years ago.

So that's our answer to 'What is climate change?'

If you've enjoyed this episode - good news! We do this every week. We take a question about climate change

and answer it. The Climate Question tackles these issues with a global

perspective, so wherever you live we'll be finding out how climate change is

affecting you and what could be done about it.

Join us as we meet experts, activists, actors, businesses, scientists and everyday people as they deal

with the world's biggest challenge – climate change.