Ocean and cryosphere act as one of our planet’s most efficient early warning systems for climate change. Both in Antarctica and Greenland, ice loss has strongly accelerated. The rate of sea level rise has more than doubled in the last two decades. Warming and acidification of the ocean have significant impacts on the global climate. The permafrost thaw further intensifies global warming. In view of these dramatic developments, the G7 Academies call for a massive reduction in greenhouse gas emissions, the global protection of marine ecosystems, the engagement of all forms of knowledge for solutions, and the enhancement international scientific cooperation and data sharing for an Earth observation and forecasting system.