We know that excess carbon dioxide (CO2) in the atmosphere is the main cause of climate change. We understand that the Earth is warming up because in the past few centuries, we burned lots of fossil fuels that took hundreds of millions of years to form and accumulate in the depths of our planet.
Fortunately, on the surface of the Earth there are CO2 hunters that spend their lives mercilessly capturing carbon dioxide. They break it down, release some of the oxygen, and then mix together the remnants with a little water and a pinch of other substances to produce seeds, fruit, leaves and other good things.
For the past two billion years, plants –our CO2 hunters– have been learning to do something that all the animals on Earth have not yet learned to do. That includes us, who, in recent (geological) times, have been dominating the planet. To understand this process we need to start with the definition of chlorophyll photosynthesis.