The manner in which the earth sustains life is of vital importance on many levels:
- Throughout geologic history, life has affected the climate system and vice versa.
- Extinctions of species, both in the geologic past and in the present day, can be linked to changes in climate.
- Unraveling past climatic changes is key to understanding present and future shifts in the climate.
- Changes in climate will result in shifting ecosystems. It is not possible to predict the specific effects of climate change on each of the world's ecosystems.
- Although the concentrations of greenhouse gases have changed throughout Earth's history, there is no natural analog to today's rapid increases in human-created greenhouse gas emissions.