Mankind has experienced an unprecedented increase in human welfare, health, wealth and numbers in the course of the 20th century. Global population rose from 1.6 billion in 1900 to over 6 billion by 2000 to 7.7 billion in 2019 and is projected by the UN to rise to 9.8 billion by 2050. Fossil fuels, coal, oil and gas, have powered our 20th century progress. In 1900 2 billion tonnes of CO2 were emitted. By 1950 this was three times higher. Today it is almost twenty times higher. According to the World Meteorological Organisation (WMO) global surface temperature, tropical forest loss, ocean acidification, ice melt, methane concentrations, primary energy use and water use have all shot up since 1950 and almost all of these at an accelerating pace decade by decade.