Why is 1.5 degrees important? - The Climate Question, BBC World Service

They reckon average global  temperatures will have risen by 1. 5°C. There's more discussion about  striving to be close to 1.

5°. We should aim for under 1. 5°.

Limiting the  global temperature rise to below 1. 5°C. One little number to rule them all.

You  must have heard of it - on the news, chanted on the streets or maybe in  your social feed. One point five. To be fair by this point if  I didn't know what it meant, I'd be too afraid to ask, but that's where we come in.

What do we mean when we  talk about 1. 5° in climate change? I'm Jordan Dunbar and I'm one of the hosts  of The Climate Question podcast from the BBC World Service.

In this episode I'm asking  simple questions and getting simple answers. To help me out I've asked DrAdam Levy  or Climate Adam as he's known on YouTube. I am a climate scientist by training  and now I work as a science communicator, climate change YouTuber and all around  kind of climate change talking person.

OK so 1. 5 to me has to be one of the most controversial, talked about, fought over and mentioned numbers, why are  people banging on about 1. 5° of warming?

So 1. 5° of warming kind of came into everyone's  consciousness as part of the Paris climate agreement. It was actually the kind of  more ambitious part of that agreement.

It said we should limit global warming to  two degrees and if we're really good let's try and limit global warming  to 1. 5° and then scientists, people in policy, people just generally  working in climate change really started to look more and more into what limiting  global warming to 1. 5 degrees would mean.

The Paris climate agreement is something that gets  talked about all the time in climate circles. It was the global climate conference back in 2015  where the majority of polluters around the world agreed to make cuts to their emissions to try  and keep global warming under control. This was the first time so many countries had  agreed to try and tackle climate change.

Our work here is done and now we can return  home to implement this historic agreement. Why 1. 5° though, why not 2° or 1.

4°? So 1. 5° manages to relatively protect us from a lot of the worst consequences of climate change, things like extreme weather events, so heatwaves, floods, droughts.

It protects animals. It means  we're more protected from food shortages, but in particular it really protects the  most vulnerable people and things on this planet. So for example low-lying island  nations could be just swept under by sea level rise if we allow global warming to reach  2° and in terms of ecosystems, coral reefs, these vital beautiful ecosystems could be  pretty much eliminated from the planet.

We've spoken to someone who knows only too  well the consequences of that sea level rise. This is a very real thing that the Maldives  is facing and struggling with right now. Rae Munavaar is a journalist working for  The Edition newspaper based in the Maldives in the Indian Ocean.

The warming caused by our  emissions causes ice caps and glaciers to melt, as well as making the oceans rise  through expanding water. What? I hear you say.

Well grab a helmet  because I'm going to blow your mind. As seawater heats up it expands.  Yes, seawater  gets bigger and literally takes up more space.

So the sea rises and that is thermal  expansion for you ladies and gentlemen, which if you live a few meters above  sea level is a real and present danger. We've been advocating because this  is our way of life, this is something we're doing for survival, it's  an existential threat for us. Everything in the Maldives is less than 10m away from a shoreline.

All of our  facilities from health care to banking to emergency response to food storage  to farming, all of this is at the shoreline. So there is nowhere we have to run, there is nothing we can do we cannot  keep building higher either. When we're talking about these amounts of global  warming firstly we're talking about an average for the entire planet, so some bits of the planet  are heating faster than others but these limits are really talking about the global average and  this warming is relative sort of to pre-industrial times before we actually got started burning  fossil fuels seriously.

In practice though, in policy and in science we actually use  the period 1850 to 1900 as the reference point because that's when we have really good  records to compare to and the important thing is that scientists and policy people are  all talking the same language. That they're all referring to the same thing when we're  talking about 1. 5 degrees.

So that we know if we're heading towards that politically we  know what the consequences of that will be. Back in 2015 though it was a fight to get the  target down to 1. 5° and unsurprisingly it was the low-lying island states, the ones most  at risk who argued to get the target down.

It has become the core of  the climate conversation. Janine Felson was a strategic  adviser with the Alliance of Small Island States back in  2015. She came onto the show and told us why she was negotiating  so hard to make 1.

5 the agreement. The days and nights and mornings of Paris are  still very fresh in my mind. We worked non-stop.

. . .

the citizens of my country and the Caribbean, who adopted 1. 5 to stay alive as  their mantra, their future looks much brighter today than it did two weeks ago. brighter today than it did two weeks ago.

We were completely euphoric 1. 5 is the ultimate defence line for small  island developing states. That is the only way in which we can provide any  hope for our children’s future.

Honestly it's great news for the whole world that  the 1. 5 degree figure is this crucial figure that the world is now focusing on because for things  like extreme weather events, heatwaves which are already devastating countries around the world  you know costing tens of thousands of lives you know limiting global warming to 1. 5° it won't  completely protect us from that but it will seriously limit the risks and the harms caused  by climate change.

OK well this brings me to the scary bit because there's been lots and lots  of headlines saying we are going to go over 1. 5 degrees warming this year. Is that true and what  happens if we do go over?

So what the 1. 5° limit refers to is the average in global temperatures.  But that's an average over several years and so if you have one freakishly hot year that doesn't  mean the limit has been breached it really has to be many years in a row over that limit for  us to have passed 1.

5° and if we do pass 1. 5° that doesn't mean game over, it's not like a  switch that takes us from everything was fine to you know world over. It's various degrees of  bad and it's not like if we pass 1.

5 degrees we then just give up and say OK well two degrees  of warming or three degrees of warming there's a world of difference between every fraction  of a degree of global warming. Because every fraction of a degree brings more likelihood of  extreme weather, so working towards not hitting 1. 7 if we're at 1.

6 means you're eliminating some  of that risk. It's not game over, there's so many more levels to play. 1.

5 is not the final  boss, it's just one of many bosses, right? Yeah for sure and you know if we fail  at that boss you know it sucks but we've just got to get ourselves  even more ready for the next boss. Reload, reload, go in.

Yes. But can we actually do it? Can we stay  under 1.

5? So it's important that we bear in mind that there's nothing  in the physics of how the atmosphere or the climate work that says 1. 5 degrees is  off the table.

That is until we have passed it. And so since we are still under  1. 5 degrees of global warming, we should really be fighting to stay  under with everything we've got.

Now if we do pass it, what does that mean? There's  a risk that some people will throw their hands up in there and say "Oh that's game over, you know,  we've tried and we failed, let's stop trying to do anything about climate change, it's the end of  the world". That's absolutely not what the science shows us, it shows us that before or after 1.

5  degrees of global warming we need to fight as hard as possible to stop burning fossil fuels so we can  stop the planet heating as quickly as possible. It's clear how important trying to keep under the  1. 5 degree limit is, but Adam how do we do it?

In some ways it's really easy to think about  and in some ways it's really complicated. So to stop the world from heating up there's one  number you need to keep in mind, which is zero and so reaching zero emissions of carbon dioxide  means transitioning as rapidly as possible away from fossil fuels to things like renewable energy,  nuclear power, battery storage, things like this and it also means making serious changes in how  we use land, so doing things like reforestation, protecting the forests that already exist. This  is what we need to do to stop global warming full stop, but to stop global warming at 1.

5°  we need to do this really incredibly quickly. So we need to reach zero emissions  overall by around the middle of the century if we want to limit  global warming to 1. 5 degrees.

So that sounds like it's not about some  amazing new technologies but government's just actually taking action, actually doing  things and not just talking about it. Yeah I think a lot of people have in their  heads that to achieve this would need some magical thing like nuclear fusion to come in and  save the day that's not at all the case we already have the tools to get us most of the way to the  net zero that we need to go for and you know over the coming decades of course new technologies  will be developed, but we need to start that transition as quickly as we possibly can and the  great news is yeah we have the tools to do that. Right, let's recap.

So we got to the 1. 5° target  to be ambitious. It lets us protect ourselves as much as we can including the many, many  low-lying islands and vital coral reefs.

If for one or two years the world is over 1. 5°  warmer that doesn't mean we've exceeded the target, it's an average. So if we do go over  it this year it's a warning it is not the end.

The other number we need to think  about is zero. Zero emissions - we have to get fossil fuel emissions  down and fast. The good news is we don't need any mad futuristic  technologies to do a lot of this.

We have the tools we need right now but companies  and governments have to use them rapidly and in huge numbers and the best available evidence  suggests once we get emissions down to zero the temperature will begin to drop. If you want to  know more we've got some other amazing explainers, like 'What is climate change? ' and 'What  is COP?

' which you can find wherever you get your podcasts. The Climate Question takes  all of the issues we've heard about and tackles them with a global perspective so wherever you  live we'll be finding out how climate change is affecting you and what can be done about it. Join  us each week to meet experts, activists, actors, businesses, scientists and everyday people as  they deal with the world's biggest challenge.