If I asked you to picture the air, what do you imagine? Most people think about either empty space or clear blue sky or sometimes trees dancing in the wind. And then I remember my high school chemistry teacher with really long socks at the blackboard, drawing diagrams of bubbles connected to other bubbles, and describing how they vibrate and collide in a kind of frantic soup. But really, we tend not to think about the air that much at all. We notice it mostly when there's some kind of unpleasant sensory intrusion upon it, like a terrible smell or something visible like smoke or mist. But it's always there. It's touching all of us right now. It's even inside us. Our air is immediate, vital and intimate. And yet, it's so easily forgotten. So what is the air? It's the combination of the invisible gases that envelop the Earth, attracted by the Earth's gravitational pull. And even though I'm a visual artist, I'm interested in the invisibility of the air. I'm interested in how we imagine it, how we experience it and how we all have an innate understanding of its materiality through breathing. All life on Earth changes the air through gas exchange, and we're all doing it right now. Actually, why don't we all right now together take one big, collective, deep breath in. Ready? In. (Inhales) And out. (Exhales) That air that you just exhaled, you enriched a hundred times in carbon dioxide. So roughly five liters of air per breath, 17 breaths per minute of the 525,600 minutes per year, comes to approximately 45 million liters of air, enriched 100 times in carbon dioxide, just for you. Now, that's equivalent to about 18 Olympic-sized swimming pools. For me, air is plural. It's simultaneously as small as our breathing and as big as the planet. And it's kind of hard to picture. Maybe it's impossible, and maybe it doesn't matter. Through my visual arts practice, I try to make air, not so much picture it, but to make it visceral and tactile and haptic. I try to expand this notion of the aesthetic, how things look, so that it can include things like how it feels on your skin and in your lungs, and how your voice sounds as it passes through it. I explore the weight, density and smell, but most importantly, I think a lot about the stories we attach to different kinds of air. This is a work I made in 2014. It's called "Different Kinds of Air: A Plant's Diary," where I was recreating the air from different eras in Earth's evolution, and inviting the audience to come in and breathe them with me. And it's really surprising, so drastically different. Now, I'm not a scientist, but atmospheric scientists will look for traces in the air chemistry in geology, a bit like how rocks can oxidize, and they'll extrapolate that information and aggregate it, such that they can pretty much form a recipe for the air at different times. Then I come in as the artist and take that recipe and recreate it using the component gases. I was particularly interested in moments of time that are examples of life changing the air, but also the air that can influence how life will evolve, like Carboniferous air. It's from about 300 to 350 million years ago. It's an era known as the time of the giants. So for the first time in the history of life, lignin evolves. That's the hard stuff that trees are made of. So trees effectively invent their own trunks at this time, and they get really big, bigger and bigger, and pepper the Earth, releasing oxygen, releasing oxygen, releasing oxygen, such that the oxygen levels are about twice as high as what they are today. And this rich air supports massive insects -- huge spiders and dragonflies with a wingspan of about 65 centimeters. To breathe, this air is really clean and really fresh. It doesn't so much have a flavor, but it does give your body a really subtle kind of boost of energy. It's really good for hangovers. (Laughter) Or there's the air of the Great Dying -- that's about 252.5 million years ago, just before the dinosaurs evolve. It's a really short time period, geologically speaking, from about 20- to 200,000 years. Really quick. This is the greatest extinction event in Earth's history, even bigger than when the dinosaurs died out. Eighty-five to 95 percent of species at this time die out, and simultaneous to that is a huge, dramatic spike in carbon dioxide, that a lot of scientists agree comes from a simultaneous eruption of volcanoes and a runaway greenhouse effect. Oxygen levels at this time go to below half of what they are today, so about 10 percent. So this air would definitely not support human life, but it's OK to just have a breath. And to breathe, it's oddly comforting. It's really calming, it's quite warm and it has a flavor a little bit like soda water. It has that kind of spritz, quite pleasant. So with all this thinking about air of the past, it's quite natural to start thinking about the air of the future. And instead of being speculative with air and just making up what I think might be the future air, I discovered this human-synthesized air. That means that it doesn't occur anywhere in nature, but it's made by humans in a laboratory for application in different industrial settings. Why is it future air? Well, this air is a really stable molecule that will literally be part of the air once it's released, for the next 300 to 400 years, before it's broken down. So that's about 12 to 16 generations. And this future air has some very sensual qualities. It's very heavy. It's about eight times heavier than the air we're used to breathing. It's so heavy, in fact, that when you breathe it in, whatever words you speak are kind of literally heavy as well, so they dribble down your chin and drop to the floor and soak into the cracks. It's an air that operates quite a lot like a liquid. Now, this air comes with an ethical dimension as well. Humans made this air, but it's also the most potent greenhouse gas that has ever been tested. Its warming potential is 24,000 times that of carbon dioxide, and it has that longevity of 12 to 16 generations. So this ethical confrontation is really central to my work. (In a lowered voice) It has another quite surprising quality. It changes the sound of your voice quite dramatically. (Laughter) So when we start to think -- ooh! It's still there a bit. (Laughter) When we think about climate change, we probably don't think about giant insects and erupting volcanoes or funny voices. The images that more readily come to mind are things like retreating glaciers and polar bears adrift on icebergs. We think about pie charts and column graphs and endless politicians talking to scientists wearing cardigans. But perhaps it's time we start thinking about climate change on the same visceral level that we experience the air. Like air, climate change is simultaneously at the scale of the molecule, the breath and the planet. It's immediate, vital and intimate, as well as being amorphous and cumbersome. And yet, it's so easily forgotten. Climate change is the collective self-portrait of humanity. It reflects our decisions as individuals, as governments and as industries. And if there's anything I've learned from looking at air, it's that even though it's changing, it persists. It may not support the kind of life that we'd recognize, but it will support something. And if we humans are such a vital part of that change, I think it's important that we can feel the discussion. Because even though it's invisible, humans are leaving a very vibrant trace in the air. Thank you. (Applause)