A temperate and high-oxygen environment appears to be required for complex life. It is well understood that Earth’s climate has broadly been stable over the planet’s history, but has oscillated between warmer and colder phases. In contrast to this, the amount of oxygen in the atmosphere has risen from trace levels to become the second most abundant gas. Understanding why this has happened is fundamental to a range of scientific work in understanding our own past, the future conditions on our planet, and our likelihood of finding life elsewhere in the galaxy. I will introduce my group’s work, where we have built a new type of ‘Earth Evolution’ computer model, able to simulate the evolving Earth system in 3D over geological time. We compare the model predictions to geological, geochemical and paleontological data in order to try to understand the key drivers beind global environmental change. Specifically, we argue that temperature oscillations are controlled by several important linked processes and do not have a single key driver, and we propose that oxygen rise over Earth history is dependent on the build-up of carbon in Earth’s crust in the form of carbonate minerals.