Cooling of the climate

 Admitted. It is Once upon a time. Nature was calm. Since the dawn of civilization we have benefited from a stable climate. But we have been pumping trillions of tons of carbon dioxide into the atmosphere. And this is wrecking our climate

 And it's destroying our oceans. We need to slow down. We need to stop. The emissions that we're doing. One way to transition to a low carbon economy is to install solar and wind to reduce the amount of CO2 we emit. But we need to go further than that. Reducing emissions is necessary but it's not sufficient. It's essential that we go further and take CO2 out. Here's why. The black curve shows what is going to happen to the level of CO2 in the atmosphere. We follow business as usual. The colored lines coming off shows what happens if all emissions cease at those points in time. That's if everybody on the planet dies. Which I'm not recommending as policy but even if that happened there will be very slow reduction in CO2. We can learn from nature in ways in which we can reflect sunlight back into space to cool the planet or suck CO2 out of the atmosphere. So we can learn from clouds and volcanoes. Forests oceans and rocks. Prevention is better than a cure. But if you can't prevent it you sure need a cure. These clouds here these show ship tracks the emissions from the ships caused clouds to form those clouds are bright they're white they reflect sunlight back into space and that will cool the planet for a bit. This is a solar radiation management technique and it could work for a short period of time. Another one is volcanoes so volcanoes when they erupt they can spray aerosols into the upper atmosphere and that reflects sunlight back into space again that could cool the planet for a short time.

And some people believe that this could be done cheaply at least to administer but the side effects are severe. So this plot here shows the blue line what happens if we don't have any way of cooling the planet. The green line shows what we could do in suppressing the temperature pushing it down by employing these techniques. But if we stopped suddenly boom the temperature goes up very quickly.

 It's called the termination effect and it could be terminal. So ultimately we will need to remove CO2 from the atmosphere. We can learn from nature by planting trees and we could have forests large areas. But there's a limit to how far we can do this because we need that land to grow crops and for biodiversity so we can only withdraw a certain amount of CO2 from the atmosphere that way. Another thing that we can do is that we can produce charcoal biochar so we grow crops and charge them and turn them into coal and bury that in the ground. It's like the reverse of coal mining but again you're constrained by how much you can do by the amount of land area that you have. So if you're constrained by land how about the oceans. Well if you put nutrients into parts of the ocean that a nutrient deficient you can courage algae to bloom as they bloom they withdraw CO2 from the atmosphere and the idea as it sinks into the deep ocean.

 But. What evidence we have here suggests that it's got limited potential and has harmful side effects. This image is of what are known as artificial trees. These are machines that are envisaged that could remove CO2 from the atmosphere. But this is an artist's impression. It doesn't really exist. It's what's known as a technological imaginary. And these processes are believed to be very expensive so don't think they have much potential but we can learn from nature in terms of rocks as rocks whether they absorb CO2 they do this slowly but there are ways in which you can accelerate the rate at which rocks weather and in that way draw down CO2 at a fast enough rate to help us avoid dangerous climate change. Now do these sound like a fairy tale. Well let me tell you what's really scary. We assume that it's going to happen. The blue curve shows what's going to happen with business as usual. Only the green curve will avoid two degree temperature rise and in order to achieve that we need net negative emissions. We need to take CO2 out of the atmosphere but can we do it. Can we do it technically. Can we do it socially politically ethically environmentally economically. We bring together the experts at the Oxford Martin School to consider this to understand is this a dream or a nightmare a vision or a delusion.

 Do we want to change the world. 

Do you want to change the world. We don't. In truth we do not seek to change the world but rather keep it as it met. It's meant to be. We seek to understand whether we can cure climate change. Can we. We do not know but we certainly can't if we do not try. So join me to see if we can learn from nature to cure climate change and live happily ever after. Thank you.