Much of the world's supplies of freshwater are stored in glaciers. But as we move into the Anthropocene, the short rains have disappeared entirely, and the long rains have become erratic The result is endemic thirst and hunger.It gets worse. Rainfall is not going to fall in the same place, or at the same times, as before. For example, in sub-Saharan Africa, in the age of the Holocene, people depended on the short rains in March and the long rains in the summer to collect water and grow their crops. Over the next two decades, 30 per cent of the world's freshwater supply is going to become unusable in a world where 1.2 billion people already do not have access to fresh water.There are three reasons why.

Without drastic preventative action now, we are going to hit the highest temperatures since our species evolved in my lifetime - and one of the biggest differences is going to be the location and dependability of the world's water supplies. Last year, the United Nations - after surveying the world's chief scientists - issued a blunt warning. It's a massive, unwitting experiment - and we have nowhere else to go if we do not like the results.Only now are we beginning to see what this new geological age looks like. We have mined and burned so many fossil fuels that we are changing the physics and chemistry of the planet we live on. Man has inaugurated a new climatological age - Crutzen calls it the Anthropocene - and the people of the 21st century are living through the transition. Over millennia, humans have evolved to live in the conditions provided by the Holocene It is all we know.There's only one problem The Holocene is coming to an end. It began to die in the 1780s, when James Watt invented the steam engine and inadvertently changed the course of history.

Since then, one creature - man - has become so numerous and so powerful that we are now altering the planet on a geological scale. This is when the world's weather settled down, and so did humanity. We began to live in villages and towns, and developed agriculture, writing, and all the other tools that make the lives we know possible. In the 10,000 years since the last glaciation, humanity has been living in a period known as the Holocene.