 Humans have been studying disasters for centuries because we've been experiencing them all the time. So we used to think of disasters as an act of God and then we started seeing disasters as an unstoppable force of nature. Our latest understanding of disasters is that they are really consequences of human decisions. To kind of explain that, the official definition of a disaster put forward by the IPCC in 2012 is that disasters are severe alterations in the normal functioning of a community or a society due to hazardous physical events interacting with vulnerable social conditions leading to widespread adverse human, material, economic or environmental effects that require immediate emergency response to satisfy critical human needs that may require external support for recovery. So that definition kind of shows you a couple of things. It's very human centric, so it's all about humans and how disasters affect us. It's an interplay between the actual physical event and the social condition of those being impacted. And disasters are about loss, so there has to be some significant negative impact, whether that's in terms of human life, whether that's economic or environmental. And it highlights that an event reaches the definition of a disaster when the coping capacity of those affected is exceeded. There are three factors that together make up a disaster. One is the natural hazard itself, so you can have a flood, a bushfire, a cyclone. And we used to think that the more intense the cyclone, the more severe the bushfire, the bigger amount of damage, but that's not the whole truth. The second factor is exposure. So exposure is where we as a society place our cities, where we place ourselves, where we place our infrastructure and the things that we value. And the third one is vulnerability. So that is that social economic condition of those being impacted. Imagine an earthquake. There's a big earthquake. Houses which are built to withstand an earthquake get shaken up, they get rattled, but they're okay. Houses that are not built to withstand an earthquake collapse and there's massive damage and loss of life. So that's about vulnerability. So it's not the hazard itself. It's the exposure and the vulnerability that play a crucial part in deciding how bad the damage and the impact is.