Xkcd dating service
The webcomic "xkcd" has produced a timeline of global warming that will startle most people.
The comic follows the timeline of Earth's temperature from 20,000 B. to the present day and it shows why global warming is such a major issue.
These engines alongside the clear cutting of forests and massive increase in fossil fuel consumption dumped unprecedented quantities of CO2 into the atmosphere.
Prehistoric, sudden shifts in climate brought about by massive volcanic eruptions or the impact of large asteroids have caused mass extinctions by making the planet suddenly hotter or cooler. It's unlikely the human race will go extinct or the environment will entirely go down to doom, but the transitional period, which could last centuries, will still be difficult.