Satellite measurements of Earth’s changing temperature, sea levels, atmospheric gases, declining ice and forest cover, for example, are one of the main ways of providing the scientific community with the data they need to improve our understanding of the Earth system and predict its future. Through ESA’s Climate Change Initiative, long-term datasets on key indicators of climate change are being systematically generated and preserved. These ‘essential climate variables’ – of which there are more than 50 – are core to the work of the United Nations Framework Convention on Climate Change and the United Nations dedicated programme on Global Climate Observation System.