 I'm going to talk about volcanic sunsets, but not just about the physics of them, also about how artists see the sky based on volcanic eruptions. This is the Grimsvottan volcano, which four years ago put a lot of sulfur up into the stratosphere. The sulfur turns into sulfate aerosols and reflects sunlight and causes climate change. And I spend a lot of my time studying that. These clouds in the stratosphere reflect sunlight and cool the surface, heat the stratosphere, destroy ozone. But that's not what I want to talk to you about today. I want to talk to you about what the sky looks like after a volcanic eruption. This is a figure from a paper about Elchichon. And you can see when the sun sets, the sunlight comes through the atmosphere. And as we all know, Rayleigh scattering will scatter the shortest wavelengths first and produce a blue sky. That's why the sky is blue. That leaves the yellow and red to go through the atmosphere. And after the sunset, it comes back and reflects off the bottom of the aerosol cloud and that produces these beautiful sunsets. Here's a picture I took in Madison, Wisconsin of what it looked like over Lake Mendota after the Elchichon eruption in 1982. Perhaps one of the most famous eruptions is that of Krakatau in 1883. And this is a drawing of what it looked like over the Thames in London by William Ascroft. Now, he was trying to paint exactly what it looked like, but other artists, the effective volcanic eruptions creeps into their paintings. So Frederick, there's one on the left what his painting looked like after Tambora and on the right without a volcano. The famous painter Turner also did that. And so you can see on the left after a volcanic eruption and on the right what the sky looks like without a volcano. But I want to talk to you mostly about the paintings by another artist. And here's his self-portrait. Can somebody tell me who this is? This is a self-portrait. That's right. He wrote his name up in the corner and it's Edward Monk, the famous Norwegian painter. He looks sort of like a businessman, doesn't he? But actually he's one of the people that put most of his feeling into his paintings. Now, he saw the Krakatau sunset and he did a series of paintings of what it looked like over Oslo. This one he called Despair. That's how it made him feel. He painted nine years after the eruption. You can see boats in the harbor and the mountains behind. But the sky has this yellow and red color. Two years later he painted one he called Anxiety. That's how it made him feel. And again you have this red and yellow brilliant color in the sky reflecting off the water. And that really inspired him. But the most famous painting that he did, as you probably all know, is called The Scream. Another version of this picture. It was painted in 1893 based on his memory of the Krakatau sunset. He actually had four different ones. This is the first one. And he explained why he did it. He said, I was walking down the road with two friends when the sun set. Suddenly the sky turned red as blood. I stopped and leaned against the fence, feeling unspeakably tired. Then he went on, tongues of fire and blood stretched over the bluish black fjord. My friends went on walking while I lagged behind, shivering with fear. Then I heard the enormous infinite scream of nature. This is my favorite version from 1910 and another time he explained again what he did. I was walking along the road one evening on one side lay the city and below me was the fjord. The sun went down, the clouds were stained red as if with blood. I felt as though the whole of nature was screaming. It seemed as though I could hear a scream. I painted that picture, painting the clouds like real blood, the colors screamed. And then he explained why he did this. He said nature is not only what's visible to the eye, it also shows the inner images of the soul, the images on the backside of the eyes. So when you as scientists are out there studying nature and it's screaming blood and fire to you, pay attention to that. Don't just pay attention to the numbers. Make sure you can think about how it makes you feel and I think that will make you better scientists. Thanks very much.