I wanted to find out how long the temperature of the Earth has been compatible with our current civilization. A quick Google search on “earth climate history” yielded a 2011 article from NASA by James Hansen, whose name I recognize as a prophet of climate science.
Hansen says our “advanced” civilization has existed completely within the 10,000 years represented by the tiny blip at the end of the lower diagram, above. As he puts it: “Civilization developed during the Holocene, the interglacial period of the past 10,000 years during which global temperature and sea level have been unusually stable.” In the context of geologic time, it’s rather remarkable that human civilization has been able to change things on Earth enough to alter the shape of this graph. I guess that’s why scientists are proposing a new name for our climate era – the “Anthropocene.”
It looks to me (from my currently ignorant point of view) that humans are poised to push the global temperature above levels that it has not seen in 5 million years. I doubt this is good! Hansen confirms that “the paleoclimate record makes it clear that a target to keep human made global warming less than 2°C, as proposed in some international discussions, is not sufficient — it is a prescription for disaster.”
For rudimentary context as to the scale of the timeline: Bipedal “hominins,” our ancient ancestors, showed up about 2 million years ago. Anatomically modern humans have been around for 250,000 years. The study of geologic time is new to me. It is a fascinating story! I’ll try to find out more.