20190418_CC

Source: BBC1

URL: N/A

Date: 18/04/2019

Event: Climate Change - The Facts

Credit: BBC1, also many thanks indeed to Geoff Chambers and to Craig at https://isthebbcbiased.blogspot.com/

People:

• Dr. Katey Walter Anthony: Ecologist, University of Alaska Fairbanks
• Sir David Attenborough: British broadcaster and naturalist
• Colette Pichon Battle: Executive Director, Gulf Coast Centre for Law and Policy
• Professor Mike Berners-Lee: Professor, Lancaster University
• Sarabpal Bhatia: Airbus engineer
• Charles Bilton: Forest fire survivor
• Justin Bilton: Forest fire survivor
• Richard Black: Director, Energy & Climate Intelligence Unit
• Chris Brunet: Resident, Isle de Jean Charles
• Juliette Brunet: Resident, Isle de Jean Charles
• Dr James Hansen: Former Director, NASA Goddard Institute of Space Studies
• Professor Matthew Hansen: Remote Sensing Scientist, University of Maryland
• Rebecca Koller: Conservationist
• Nigel Lawson: Baron Lawson of Blaby, Chairman of the Board, GWPF
• Professor Richard Lazarus: Professor of Law, Harvard University
• Professor Tim Lenton: Climate Scientist, University of Exeter
• Professor Michael Mann: Climatologist, director of the Earth System Science Center, Pennsylvania State University
• Professor Mark Maslin: Climate Scientist, University College London
• Professor Catherine Mitchell: Professor of Energy Policy, University of Exeter
• Chief Albert Naquin: Chief, Isle de Jean Charles
• Sunita Narain: Director General, Centre for Science and Environment
• Naomi Oreskes: Science historian and co-author of Merchants of Doubt
• Professor Andrew Shepherd: Climate Scientist, University of Leeds
• Dr. Bergur Sigfusson: Geochemist, Reykjavik Energy
• Dr. Sandra Osk Snaebjornsdottir: Geochemist, Reykjavik Energy
• Chris Stark: Chief Executive, Committee on Climate Change
• Dr Peter Stott: Leader of Climate Monitoring and Attribution Team, UK Met Office
• Greta Thunberg: Climate change activist

David Attenborough: Right now, we are facing our greatest threat in thousands of years - climate change.

Naomi Oreskes: For a long time, climate change was something that scientists were predicting that would happen in the future. But that's no longer the case.

Richard Lazarus: What we're doing right now is we're so rapidly changing the climate, for the first time in the world's history people can see the impact of climate change.

Mark Maslin: Greater storms, greater floods, greater heatwaves, extreme sea-level rise.

Michael Mann: All of this is happening far faster than any of us thought possible.

David Attenborough: Scientists across the globe are in no doubt that at the current rate of warming, we risk a devastating future.

Peter Stott: It's difficult to see how the population of the world will actually feed itself.

Sunita Narain: It's happening in your world, it's happening in my world.

Richard Lazarus: Time is running short.

Michael Mann: There's still time, but there isn't much time left.

David Attenborough: The science is now clear that urgent action is needed.

Activist: We're at a tipping point! We can change history! Right now!

David Attenborough: What happens now and in these next few years will profoundly affect the next few thousand years. What can be done to avert disaster and ensure the survival of our civilisations, and the natural world upon which we depend?

Greta Thunberg: It's our future - we can't just let it slip away from us.

David Attenborough: Standing here in the English countryside, it may not seem obvious but we are facing a man-made disaster on a global scale. In the 20 years since I first started talking about the impact of climate change on our world, conditions have changed far faster than I ever imagined. It may sound frightening but the scientific evidence is that if we have not taken dramatic action within the next decade, we could face irreversible damage to the natural world and the collapse of our societies. We're running out of time but there is still hope. I believe that if we better understand the threat we face, the more likely it is that we can avoid such a catastrophic future. Our climate is changing because of one simple fact - our world is getting hotter.

Peter Stott: We have temperature records going back over a hundred years. There are dips and troughs, and there are some years that are not as warm as other years, but what we've seen is this steady and unremitting temperature trend. Twenty of the warmest years on record have all occurred in the last 22 years.

David Attenborough: It's not just Met Office records that are showing this trend. Data from the US Climate Center, NOAA, the Japanese Met Office and NASA all show the same sharp rise in temperatures. When scientists first became concerned about these increasing temperatures, nobody could be sure exactly what was driving them. Four decades of research later, on land, at sea and in the far reaches of our atmosphere, the evidence is now unequivocal.

Peter Stott: What's striking is that warming trend cannot be explained by natural factors but is caused by human activities, in particular our use of fossil fuels.

Naomi Oreskes: The problem is that everything we do - our entire economy, from the moment you wake up in the morning and turn on the light or look at your cellphone to the moment you go to bed at night, and even then because your cellphone is still drawing power at night - I mean, we are all using energy all the time and in the industrialised world that energy is almost entirely fossil fuels.

Peter Stott: We burn fossil fuels - coal, gas and oil - to power our energy generation, to heat our homes, to drive our factories, to power our cars and our trains and travel around the world.

Naomi Oreskes: And when we burn fossil fuels, it produces carbon dioxide as a waste product.

James Hansen: Carbon dioxide acts like a blanket - it absorbs the heat radiation from the Earth's surface and that - that keeps the surface warmer than it would be, otherwise.

Richard Black: The problem is, what we're doing now is we're adding extra carbon dioxide and other greenhouse gases, so we're increasing the thickness of this blanket.

James Hansen: Before we started to burn coal, the amount of carbon dicoxide in the atmosphere was about 280 parts per million. It's now over 400 parts per million, and the planet gets warmer and warmer.

David Attenborough: We have pumped so much carbon dioxide into our atmosphere, that our world is now around 1 degree Celsius hotter than it was in pre-industrial times. This warming is enough to bring about the raft of effects we call climate change.

Peter Stott: One degree Celsius global warming may not sound like much, but it's having a dramatic effect on our weather.

Michael Mann: You warm up the planet, of course you're going to get more intense and more frequent heatwaves. You're going to dry out the soils, so you're going to get worse drought.

Peter Stott: We're seeing extreme heat in southern Africa, Japan, North America, in the UK as well.

Female newsreader: It is officially the hottest day of the year, so far. The heat has been causing health...

Richard Black: Often the question is: did climate change cause a certain event? And you can never really answer that question. But what scientists do is to look at whether climate change made a certain event more or less likely, or more or less intense.

Peter Stott: Last year we had a heatwave that was actually the joint warmest on record, alongside 1976. And we've been analysing this, here at the Met Office. What that showed us was that the chances of that heatwave had increased by about 30 times, so it's now about 30 times more likely that we had that heatwave than we would have had, without climate change.

Female newsreader: Today the mercury hit a scorching 35 degrees Celsius...

Peter Stott: So it doesn't mean to say that every single weather event is due to climate change. But what climate change does mean is that with the baseline climate having changed, then the frequency of the extreme temperatures is increasing. And that has a substantial effect.

David Attenborough: In November last year, when temperatures in Cairns, Australia, hit 42 degrees, even creatures specifically adapted to heat were unable to survive.

Woman's voice: They're just everywhere...

Rebecca Koller: When we got here in the morning, it was the first time, really, we saw it. There were just dead bats, as far as the eye could see. There was the deafening sound of babies crying...

Woman's voice: And we're just... [Tearful voice.] I don't know where to start...

Rebecca Koller: So we just started finding [?] babies, basically.

Man's voice: A little baby, attached to its dead mum.

David Attenborough: Like all species, flying foxes have ways of dealing with the conditions of their environment. But it seems their usual cooling methods are no longer enough for the kind of temperatures Australia is now facing. Last year, temperature records were broken across the country.

Peter Stott: Scientists have shown that it's simply inconceivable that you would see these temperatures without the fact of climate change.

Rebecca Koller: We saved about 350 - the rest are dead. So, over 11,000 died, from that [inaudible]. And if you had two more events like we had, then the species are gone.

Man's voice: It's climate change in action. We need to wake up. [Sad music].

David Attenborough: I've seen for myself that in addition to the many other threats they face, animals of all kinds are now struggling to adapt to rapidly changing conditions.

Catherine Mitchell: Think of the equator. As climate change occurs, that kind of central part of the world becomes increasingly uninhabitable.

James Hansen: If climate change is too fast, we're pushing them off the planet, in effect. We're causing extinction of species already, and that's irreversible.

David Attenborough: Scientists believe that 8% of species are now at threat of extinction solely due to climate change. This isn't just about losing wonders of nature. With the loss of even the smallest organisms, we destabilise and ultimately risk collapsing the world's eco-systems, the networks that support the whole of life on earth.

Peter Stott: What's been happening in recent years is really showing us what one degree Celsius really means, not just for wildlife but for people, for their safety, for their livelihoods and for their futures.

David Attenborough: As temperatures rise, the threats we face multiply. Last year saw record-breaking wildfires take hold across the globe.

Voice-over mix: ...firefighters are working around the clock ... to be seen to be believed... Australia is seeing some of its worst fires in years...

Michael Mann: We've seen wildfires break out in Greece, and even in the Arctic.

Male newsreader: ...wildfire sweeping across some of the coldest countries on earth...

Michael Mann: We've seen a tripling in the extent of wildfire in the Western US, in California...

David Attenborough: The fires that swept through California last year caused 24 billion dollars worth of damage. 106 people lost their lives.

Naomi Oreskes: We're not just talking about an inconvenience, we're talking about people's lives, their livelihoods and their communities being damaged.

Peter Stott: Wildfires need an ignition source.

Man's voice: ..what?... Oooh ... big...

Peter Stott: Maybe cigarette butts or lightning, and then you need the weather conditions that are conducive to that fire and that fire spreading.

Man's voice: .. Oooh... Do I go? Don't wanna be trapped...

Peter Stott: Research has shown that the chances of having these very hot dry conditions has increased as a result of climate change.

Man's voice: ... oh my God! Keep going, don't stop... Easy, easy...

Justin Bilton: That was a dead end road so we knew that our only option was to drive forward, and all sides of the road were just completely engulfed in flame.

Man's voice: The car's heating up - it's going to explode...

Charles Bilton: He's going: "Dad! Dad! We're gonna die, we're gonna die", and I said: "No, we're gonna be fine, y'know.."

Man's voice: ...Oh Jesus God, help us...

Charles Bilton: I stayed calm. I think being a father, you're trying to keep your son calm too, at that point.

Man's voice: ...We're good, we're good..

Justin Bilton: We could hear the trees literally exploding and falling all around us.

Man's voice...Please God help us...

Charles Bilton: A large branch went right over the top of the car, and the whole top of the roof was burning, and we didn't realise it, and there was a tree down.

Man's voice: ... [Shouts.]...

Justin Bilton: That was the moment when I really thought that we might die.

Man's voice: ...Oh God...Pop, pop.. Back it up... Back it up, yeah..

Justin Bilton: I said, put the car into reverse, and I had to drive backwards through everything we had already passed through to the lake shore.

Charles Bilton: And this one little boat was down there watching the fire. And we were able to wave them in to help us get out of there. That to me was just a miracle.

David Attenborough: But it's not just through extreme heat events that climate change is having an effect. It's changing our weather systems in other ways.

Peter Stott: This is a basic result of physics. With a degree Celsius of warming, there's more moisture evaporating off the oceans.

Michael Mann: When there's more moisture in the air, you're gonna get more rainfall, you're gonna get super storms and force flooding events. We are seeing the impacts of climate change now, play out in real time. They're no longer subtle.

Sunita Narain: You've had the worst rain in China, in Japan, you've had a deluge in Kerala.

Newsreader: ... the crisis deepens for hundreds of thousands in Kerala...

David Attenborough: Whilst they can't all be attributed to climate change, last year's extreme weather events meant that millions of people needed humanitarian aid.

Sunita Narain: Join the dots. It's happening. It's happening in your world, it's happening in my world. And, let's be very clear about this. It is going to get much worse.

David Attenborough: Climate change goes far beyond the weather. Thousands of miles away, and out of sight of most of us, another threat is building. Earth's ice, frozen for millennia, is melting.

Andrew Shepherd: Earth's temperature has risen by what most people would think is a small amount over the past century, by about a degree centigrade, and that's too much for earth's ice to withstand. In the last year we've had a global assessment of ice losses from Antarctica and from Greenland, and they tell us that things are worse than we'd expected. The Greenland ices sheet is melting. It's lost four trillion tons of ice, and it's losing five times as much ice today as it was twenty five years ago. If you go to the Southern hemisphere, in the past, most of the models predicted that Antarctica would grow. That's not the case. Antarctica is losing three times as much ice today as it was twenty five years ago. In Antarctica, really small changes in ocean temperature in particular can melt a lot of ice. The ocean is only about half a degree centigrade warmer than it should be, but that's melting colossal amounts of ice from enormous glaciers. The water that melts from the ice sheets ends up in one place, and that's the oceans, and that's when it starts to affect people around the rest of the planet.

James Hansen: Sea level has been stable for several thousand years. But if the ice sheets lose icebergs, faster and faster to the ocean, the sea level goes up.

Andrew Shepherd: We know that sea level has already risen by about twenty centimetres in the last hundred years.

David Attenborough: Rising seas are displacing hundreds of thousands of people from already vulnerable coastal areas in the South Pacific, Indonesia, Bangladesh.

Colette Pichon Battle: The impact on families is going to be something that I don't think we could ever prepare for. In the United States, Louisiana is on the frontline of this climate crisis. It's losing land at one of the fastest rates on the planet, at about the rate of a football field every forty five minutes.

David Attenborough: The Isle de Jean Charles was once home to 400 people, but subsidence caused by oil and gas extraction, and now, rising seas, means that in the last six decades, much of it has disappeared.

Chief Albert Naquin: Before, this was all land. But due to sea level rise, slowly but surely it's washing away. What we're looking at here is where I was born and raised, in 1946. Sad, very very sad to see what happened to my mum and dad's home, and where they raised us at. I want to finish my life as well over here.

Colette Pichon Battle: For the people on Isle de Jean Charles, they're running out of options. And now what we see is just 10% of what used to be there. We have been working with the state to move an entire community. This is the first time the federal government of the United States has offered dollars for the relocation of folks due to climate change.

Chris Brunet: When it comes to relocation, this is the only place I've ever known as home. I don't want to abandon it, I don't want to forget it.

Juliette Brunet: A lot of people say that this land that we're living on won't be here in 20 years from now. That's kind of hard to think about, where you grew up isn't going to be here any more.

Colette Pichon Battle: The residents of Isle de Jean Charles have been labelled as the first climate refugees in the United States. And that may be true. But what we know for sure is that they won't be the last.

David Attenborough: Sea levels are not only increased by melting ice. The world's oceans are expanding because they're getting warmer. Over 90% of the increased heat trapped in our atmosphere has been stored in the oceans. I've witnessed the devastating effect this is having. In the last three years, repeated heat stress has caused a third of the world's corals to first bleach and then die.

Michael Mann: Our generation is going to be responsible for the loss of one of the most majestic ecosystems on the face of the Earth. We're literally watching the death of this natural wonder.

David Attenborough: In many ways, what's happening now across the world doesn't come as a surprise. Much of what we're now experiencing, scientists warned about over 30 years ago.

James Hansen: What we're seeing at the moment is exactly what we predicted. In the summer of 1988, I testified to Congress. I said I was 99% confident that this was a real, physical effect of the increasing carbon dioxide.

Richard Black: James Hansen was absolutely a pioneer in trying to reach the public and politicians. He played a major role, there's no doubt, in putting climate change on the international agenda.

James Hansen: The short-term response was pretty good. The politicians were saying the right things, that we should avoid dangerous human-made changes to climate. It's just that the policies needed to achieve that were never adopted.

Naomi Oreskes: There are many reasons we haven't acted on climate change. Science is definitely part of the story. The science is complicated.

Richard Black: Economists had to look at, "OK, what are the costs are going to be?" And then technologists had to work out, "Well, what actually can we do about it?" And that's one of the reasons why it took a long time for governments really to put policies in place. However, there was also resistance. Let's be honest about this. There are incumbent industries that then, they knew about climate change, but they didn't really want anything to happen.

Naomi Oreskes: The organisations that had the most to lose by acting on climate change were the fossil fuel companies. The most profitable industry possibly in the history of mankind, making huge profits. They wanted to continue that.

Richard Lazarus: Many of those industries, basically the oil and gas industry, the fossil fuel industry, they undertook a quite concerted campaign to confuse the science and confuse the message.

Richard Black: This is industry-funded and industry-driven. Fossil fuel companies engaged PR consultants who used exactly the same tactics that have been used by the tobacco companies, and there's ample documentation.

Naomi Oreskes: The basic strategy is to cast doubt on the science to promote the message that we don't really know, there isn't a consensus and it will be too expensive to fix anyway. The cycle of denial has worked. And even today, the President of the United States says that it's not true.

Richard Black: In the UK, we have the Climate Change Act from 2008, which was the first law anywhere in the world to make a legally binding target for reducing greenhouse gas emissions. But what we've also seen here is a number of people in politics who've decided really to campaign against action on climate change.

Nigel Lawson [old footage]: There's plenty of evidence that warming will bring benefits as well as maybe disadvantages.

David Attenborough: The arguments have been, well, climate change is happening but it may not be that serious.

Nigel Lawson [old footage]: There are huge benefits from a warming planet. In the IPCC's own report, there's fewer deaths from cold-related diseases.

David Attenborough: They say we should just adapt to it rather than try to reduce greenhouse gas emissions. And of course that's very attractive to politicians. Because to decide not to do something is much more comfortable.

Naomi Oreskes: I think that many of us were willing to hear that message because we too depend upon fossil fuels for our lifestyle. So we're all implicated in this economic system, but it's not like we're all equally responsible, right?

Richard Black: There's no doubt that that seeding of doubt has slowed the transition to a clean-energy economy.

James Hansen: We haven't entirely wasted the 30 years but it would have been so easy to solve the problem if we had started gradually to make fossil fuels more expensive and develop the technologies to replace them. But we didn't do that. And now there are consequences.

David Attenborough: Greenhouse gas emissions have continued to rise and the problem is getting harder to solve. The world's great forests play a vital role in determining the balance of carbon dioxide in our atmosphere. Trees and plants absorb carbon dioxide, using it to build their leaves, stems and roots. In this process of photosynthesis, they have sucked up and stored nearly a third of our emissions.

Matthew Hansen: The main driver of climate change is greenhouse gas emissions. Forests are one of our ways out. They are like the lungs of the planet. They are big climate regulators at a global scale. My work has always been about monitoring the land surface and forest. Since 1972 till now, Landsat has been tracking and taking pictures of the Earth's surface. In 2008, the US government says it's open free of charge and accessible over the internet. Millions of images, automatically. It's just this huge leap in capability. It was only then where we saw the whole planet. And when you see the whole, it was a bit of a revelation. And, yeah, the alarm bells go off. These warm orangey tones, that's forest disturbance, that means forest was removed. We didn't know that was going on. Colombia, Peru, Paraguay, Bolivia. We can go anywhere and see actual forest be cleared. It usually starts with logging. Rainforests are cleared and burned. They then replace it with soybeans, rubber, pasture for cattle. But one of the big drivers is palm oil. Palm oil is like a magical fruit. We all have palm oil in our houses right now.

Mark Maslin: It's found in almost every good you can think about. It's in soaps, it's in shampoo. It's in chocolate, it's in bread. It's even in crisps. What we're doing, accidentally and inadvertently, is actually causing deforestation in other countries because of our demand for this product.

Matthew Hansen: That means the natural system is not working. Habitats are disappearing. But also when these high carbon stock forests, that are centuries old, are cleared and burned, CO2 is added to the atmosphere. Those emissions go up and warm the planet. When you look at our maps, our results are showing that it's accelerating. It almost looks like a contagion. You know, it looks like a disease across the planet. I mean, the ever-increasing pattern. If we continue this level of deforestation, we'll take it all. And our ability to mitigate climate change and turn the story around becomes really vanishingly small.

David Attenborough: Trees are now being cut down and burnt at such a rate, that nearly a third of our carbon dioxide emissions are caused by deforestation.

Matthew Hansen: It sucks. I'm a pretty light-hearted, optimistic guy. But just looking at this data, you just look at the stories, I'd like to see some evidence of a really strong, strong kind of unified political response that was more than an aspiration on a kind of piece of paper, right? That would be cool.

David Attenborough: Looking ahead to the future, we know that if we continue releasing carbon dioxide into our atmosphere, temperatures will keep rising and the consequences will get progressively worse. But do we know how much worse?

Mark Maslin: There are thousands of scientists around the world, in almost every single country, working to understand what will happen in the future if we don't act, we don't do more. So we use really powerful climate models, which are numerical representations of the whole of the Earth system. The oceans, the land, the atmosphere and the ice on the planet. And then we drive it with increased carbon dioxide, based on predictions of the future and then we see what the model does. They predict that if we carry on as we are now, where CO2 continues to increase, we would hit 1.5 degrees global warming by between 2040 and 2050.

Mike Berners-Lee: We're on course to go through 1.5 degrees in just a few decades' time, and the models differ slightly as to exactly when. And not long after that, we're on a trajectory to go through two degrees.

David Attenborough: Whilst we don't know exactly what a two degree warmer world will look like, there's growing evidence about the consequences of crossing this threshold.

Mark Maslin: We know that with increased storms, increased floods, droughts and heat waves, production of food will be more problematic.

Peter Stott: It really becomes difficult to see at such levels of warming how we're going to maintain our agriculture, such that the population of the world can actually feed itself.

Mark Maslin: Ensuring people have access to clean, safe drinking water will become much more difficult.

Sunita Narain: Developing countries are at the front line of this battle.

Richard Lazarus: Those parts of the globe which will suffer the most and the soonest are not those parts of the globe which have actually loaded all those carbon dioxides into the atmosphere in the first instance.

Sunita Narain: But you have to understand, this is also a crisis for the world. The fact is that if the poor are suffering today, then the rich will also suffer tomorrow.

David Attenborough: As we look further into the future, predicting how our climate system might behave becomes more complex.

Tim Lenton: There's uncertainty in climate projection, not least because we don't know what our generation when we're older is going to be doing and what the future generations are going to be doing.

David Attenborough: But based on our current trajectory, the various models predict that by the end of the century, our planet will be somewhere between three and six degrees hotter.

Mark Maslin: Even if we are looking at the bottom end of predictions, that's still really bad.

David Attenborough: Over 600 million people live in coastal areas that are less than ten metres above sea level.

Mark Maslin: Some models predict if we don't do anything to curb climate change, then we could be looking at 80 centimetres to a metre of sea level rise by the end of the century.

Peter Stott: So sea level is dangerous for us in the UK, as indeed elsewhere. The main impacts of what might seem a gradual rise of sea level is the risk from storms, surges of sea that we've never seen before.

James Hansen: If we lose all our coastal cities, we've got a different planet and we've got a economic situation which is out of control.

David Attenborough: While there's a lot we understand about what the future might hold, the big fear is that there may be other, more extreme dangers lurking beyond those we already know about. Scientists call these tipping points.

Tim Lenton: A tipping point is where in a part of the climate system, just a little bit of extra warming could nudge it into a different state, an irreversible change.

David Attenborough: At the moment, it is our ongoing emissions that are driving global temperatures up. But if we cross tipping points, that could spiral beyond our control.

Tim Lenton: If we imagine a map of the world, it turns out that there are climate tipping points dotted all around it. Greenland and West Antarctica could be tipped into irreversible meltdown. There are major ecosystems that we could tip into an alternative state. For example, triggering a climate-induced dieback of the rainforest, turning it into a savannah.

Mike Berners-Lee: Once you've crossed a tipping point, that's it. You've triggered a catastrophic change. It's going to carry on getting even hotter, because you've triggered something that you can't undo.

David Attenborough: One of the potential tipping points scientists have identified involves a greenhouse gas locked underground.

Mark Maslin: We know that there's large amounts of methane stored in the permafrost in the Arctic, and we're worried that as that permafrost starts to actually unfreeze, the methane trapped underneath will start to bubble up.

Katey Walter Anthony: Few bubbles down in there. When we look down into the ice, we see white pockets of gas. We can see that there are bubbles in the surface layer and then there's a whole column of bubbles that stacks up. When this ice sheet melts, the gases are released into the atmosphere and you can actually hear the gases coming out. [Gas hisses.] So look. These flares that we're doing demonstrate that the bubbles contain methane. It's a very potent greenhouse gas.

Mark Maslin: Methane is 21 times more powerful as a greenhouse gas than CO2. So you can imagine a large amount of gas burping out of the permafrost actually causing the acceleration in the global warming that we see already happening.

Katey Walter Anthony: You look out across the millions of lakes in the Arctic, you start to wonder just how much methane all of these lakes could release.

David Attenborough: The future looks alarming indeed, but it's not without hope. There is still time, if we act now with determination and urgency. What do governments, industries, nations and we, as individuals, need to do to change our course? At the 2015 United Nations climate summit in Paris, for the first time ever, nearly every country in the world came to an agreement. It set an objective to hold temperatures below two degrees and try to limit warming to 1.5.

Mark Maslin: If we want to try and keep the global climate to 1.5 degrees, we have to halve our carbon emissions by 2030 and then hit zero carbon emissions globally by 2050.

David Attenborough: This poses a huge challenge, as emissions must be cut from almost every part of the economy. But 25% come from how we produce electricity and heat, and alternatives are already within our grasp.

Naomi Oreskes: It's actually not that complicated. We need to shift our energy system away from fossil fuels that produce greenhouse gases and towards renewable energies that don't.

Catherine Mitchell: Every country has got a different resource. In Norway, you've got an awful lot of hydro power. If you're in India or Morocco, there's lots and lots of sun. The problem was that renewables were much more expensive than fossil fuels.

Richard Black: But what's happened recently is rapid falls in the price of renewable energy.

David Attenborough: Solar power has led the way with this.

Chris Stark: Germany went first with of many of the key technologies in solar, and China really picked up the baton.

Naomi Oreskes: There's tremendous technological innovation taking place around the world. Solar power is now the cheapest form of newly installed electricity in more than 60 countries.

Michael Mann: We're seeing a huge growth in renewable energy. Despite entrenched fossil fuel interests, they've been unable to stop that transition. And we've got to do even more.

Chris Stark: In the UK, for a long time, we've been considering future energy sources. It used to be ten, 20 years ago that nuclear power offered a relatively cheap way through. And one really good advantage of nuclear is that it doesn't produce emissions. But what's become clearer recently is that some technologies are performing better than others. And increasingly, that's been about wind.

David Attenborough: Here in the UK, we are building some of the biggest offshore wind turbines in the world. The bigger the turbine, the more wind can be captured. Just one revolution of these blades can power a house for a day.

Chris Stark: With the increased capacity, wind resource is about to become as cheap and much cheaper in the future, than fossil fuels.

David Attenborough: So far, around 30% of the UK's electricity comes from renewable sources. If that is to continue to grow, we'll need to develop parallel systems to keep our energy reliable and store what we produce.

Chris Stark: The bit that comes next, that means that we have to decarbonise industry and we've got to decarbonise the transport sector. And that means using things like electric vehicles, battery-powered vehicles, potentially even hydrogen-powered vehicles.

Catherine Mitchell: We know what we have to do. We really have to get on and do it.

Chris Stark: And this is the political decision and the brave decision that needs be taken. Do we incur a small cost now, not insignificant cost, let's be clear on it, or do we wait and see the need to adapt? And the economics is really clear on this, that the costs of action are dwarfed by the costs of inaction.

David Attenborough: If we take this path now, we could potentially buy ourselves time to crack some of the most challenging sources of emissions, like aviation.

Sarabpal Bhatia: One of the major barriers to obtaining electric flight is the power that we can get from batteries today. But we are seeing strides being made and seeing a reduction in the weight of these batteries.

David Attenborough: Recently, the world's first fully electric plane made it across the Channel.

Sarabpal Bhatia: This was a single-passenger 60 kilowatt power jet. Now we're trying to retrofit a 20 tonne aircraft and get it flying. We'll be replacing one of the engines with an electric motor driving the fan. We're going to take these hybrid electric systems and test them in the air, test them in flight at different altitudes and different temperatures. And this is going to give us the key to understand how we might integrate these systems for future aircraft designs.

David Attenborough: To limit warming to 1.5 degrees, as well as reducing the amount of carbon dioxide we release into the atmosphere, we need to find ways to reduce the vast amount that's already there.

Chris Stark: There's a great deal of interest in the kind of technologies that we might have that could actually remove carbon dioxide from the atmosphere. Now, the first thing to say is we already have these technologies and they're called trees.

Mark Maslin: If we reforest and rewild vast areas of the world, then we can lock up huge amounts of carbon that is currently in the atmosphere.

Chris Stark: In the future, there are other technologies that might work. Like direct air capture.

Bergur Sigfusson: This is one of the world's first carbon collectors. Air is sucked into the collector. Inside there is a filter unit that absorbs CO2. The CO2 sticks to the filter. And then it's dissolved in water. And under high pressure, we pump it down to 1,800 metres. It's the same as the depth of the Grand Canyon. And there it enters the bedrock.

Sandra Osk Snaebjornsdottir: This is a core taken from deep within the ground at the site where we injected our CO2. It's basalt. The water just flows through these pores and reacts with the rock. So the white that we see here is the CO2 turned into stone. So it's not affecting our atmosphere.

David Attenborough: Technologies like this may be able to help us in the future, but to meet emission targets, action is needed now. Can what we do as individuals make a difference?

Mike Berners-Lee: So the average UK person has got a carbon footprint of roughly 13 tonnes of carbon dioxide equivalent, per person, per year. And that's everything that they buy and do, traced right back down the supply chain. And we can pick a few things to start with that will make a really significant difference.

Catherine Mitchell: We should be making our homes as energy efficient as possible.

Richard Black: That can be as simple as getting your house insulated so you waste less energy, which by the way, will save you money.

Mike Berners-Lee: Everything that we buy, even if we can't see it, has a carbon footprint. From smartphones, to clothes, to furniture.

Catherine Mitchell: We've all become completely used to buying things produced using fossil fuels. A lot of the time we really don't know that.

Mike Berners-Lee: Take a washing machine, mainly made out of metal and that starts off with a mine. Ore is going to be taken to the blast furnace to extract the metal. An enormous amount of fossil fuel is going to be used. And then parts are turned into components, more emissions again. Lastly, it's shipped all over the world to arrive at your local shop. So we need to think about buying less physical products. When we do so, buy higher quality and then make it last.

Richard Lazarus: We've been such a wasteful world, especially in the more developed parts of the world. You actually can be far less wasteful and not affect the quality of your life at all.

Mike Berners-Lee: Food is about a quarter of our carbon footprint in the UK. If we take three steps, then we can cut that in half. First step, just to eat everything that we buy. In the UK, we waste an enormous proportion of our food. And second, avoid air freighted food which is about 100 times as impactful as putting it on a boat, and suddenly becomes a carbon disaster. Lastly, the most important thing to do is to reduce our meat and dairy consumption, especially beef and lamb.

Chris Stark: The problem is not traditional farming techniques. The problem is with intensive farming.

Mike Berners-Lee: It takes a lot of resources to rear an animal, and cows and sheep are especially high impact because they ruminate, which means they burp up methane. And the science on this is absolutely clear cut. Our studies have shown that if we take these three steps, we could knock perhaps even two tonnes off the average UK person's carbon footprint.

Chris Stark: These things really do matter. They only get you part of the way. But again, if we don't have them, we won't make the final target.

David Attenborough: What happens next is up to us all. I truly believe that together we can bring about the transformative change that is needed.

Mike Berners-Lee: Where your influence really kicks in is the way that you push for the cultural change that we need to see and the political change that we need to see.

Catherine Mitchell: People being able to make their voice heard really matters.

Richard Lazarus: You should not underestimate your own power or underestimate your own significance to change people's minds and change people's behaviour.

Greta Thunberg: When I was younger, I had lots of plans of becoming different things, everything from an actor to a scientist. But then my teachers in school told me about climate change. That was sort of an eye opener to me. The more I read about it, the more I understood how dangerous it was for everyone. I stopped going to school. I stopped talking because I was just so sad. And then... that made me very concerned. One day, I decided that this was enough. I wasn't going to accept this any more. My future and everyone else's future is at risk and nothing is being done. No-one is doing anything. So I have to do something.

So I sat myself down on the ground outside the Swedish parliament and I decided that I wasn't going to go to school. The first day I sat all alone. Then the second day, people started joining me. I wouldn't have imagined in my wildest dreams that this would happen. It happened so fast. It is amazing that tens of thousands of children all around the world have done the same thing as I did... ..saying that why should we go to school, if there's no future? And why should we learn facts when the most important facts don't matter?

I've learned that you are never too small to make a difference. And if a few children can get headlines all over the world, just by not going to school, then imagine what we could all do together if we really wanted to. Change is coming, whether you like it or not. We still have time to turn everything around, to pull the emergency brake and to take action. But that short period of time isn't going to last for long.

David Attenborough: There's a message for all of us in the voices of these young people. It is after all their generation who will inherit this dangerous legacy. We now stand at a unique point in our planet's history, one where we must all share responsibility both for our present wellbeing and for the future of life on Earth. Every one of us has the power to make changes and make them now. Our wonderful natural world and the lives of our children and grandchildren, and all those who follow them, depend upon us doing so.