What happens high in the sky affects everyone’s life down on the ground. The extra amount of energy from solar radiation trapped in the atmosphere by greenhouse gases from burning fossil fuels affects numerous most relevant processes in atmosphere and weather patterns – from heat and droughts to rain and floods. Weather extremes are increasing. Our climate changes, a climate which has been remarkably stable during millennia of human civilization. Earth system science disentangling the mechanisms at work is the very foundation for assessing the risks.