Climate science now unequivocally states that human activities have caused the global warming that is observed to date. This state of knowledge builds on centuries of scientific advances in the understanding of the climate system, from multiple lines of evidence - observations, theory, process understanding, and numerical modelling. This presentation will build on key findings from the Sixth Assessment Cycle of the Intergovernemental Panel on Climate Change, and place the current scientific understanding in this context of climate science history, and lay out what is the current state of climate, with the observed intensification of global and regional changes, and what are physically plausible futures, unpacking how science underpins the understanding of the climate emergency. We will encompass the scientific understanding of human influence on the global carbon cycle and sources and sinks of greenhouse gases, of human influence on observed climates (attribution), and insights from past climate evidence (paleoclimatology). We will explain how advances in the understanding of the Earth system are crucial to inform climate action through the understanding of current and future changes in global and regional climatic impact-drivers, as a function of human influence and global warming levels, and through the understanding of the geophysical constraints for halting global warming, in particular the specific roles of cumulative emissions of carbon dioxide and short-lived climate forcers. Finally we will provide a physical climate science perspective on the current state of climate action, following the outcomes of the United Nations Framework Convention on Climate Change 28th Conference of Parties (COP28).