The Swedish astronomer Anders Celsius (1701–44) was arguably the world’s first true Earth scientist. In Celsius: A Life and Death by Degrees, Ian Hembrow reveals what his extraordinary, but tragically short, life and career can teach us about our today and humanity’s tomorrow. Our modern understanding of many of the Earth’s most awe-inspiring phenomena owes much to a modest and quietly spoken, eighteenth-century Swedish astronomer, who died of tuberculosis aged just 42. From the Northern Lights, air pressure and magnetism to the shape of the planet, sea levels and early studies of climate change, Celsius unravelled some of the greatest mysteries of his time. Best known for inventing the 100-point ‘centi-grade’ scale, Celsius’ name also now frames humanity’s future in the international targets to limit average global temperature increases to no more than 1.5 degrees above pre-industrial levels.