The Earth's tropical zone is expanding and could have far-reaching impacts, especially for Australia, according to a report published in Geographical Research. Although they occupy a zone between the Tropics of Cancer and Capricorn, tropical climates occur within a larger area of around 30 degrees either side of the equator, with the dry, subtropical zone —  where we find the words's great warm deserts —  lying adjacent to this broad region. Since 1979, the Earth's tropical atmosphere has been expanding by 56 kilometres to 111 kilometres per decade in both hemispheres and are projected to continue to expand —   driven largely by human activities, primarily the emission of greenhouse gases and black carbon (released though the incomplete combustion of fossil fuels, biofuels, and biomass), as well as warming in the lower atmosphere and the oceans. And as these subtropical zones shift, droughts will worsen and overall less rain will fall in most warm temperate regions. To find out more go to Expansion of the tropics: revisiting frontiers of geographical knowledge.