Climate Change Causes Civilization (and vice versa)
Humans evolved about 200,000 years ago in Africa. For most of that time, we lived a hunter-gather lifestyle. Oh, there were fits and starts at agriculture, but nothing really "took". And then, about 10,000 years ago or so, we figured it out. We domesticated wheat and barley and other grains, and then we started herding cattle, wheat, and goats. What was it that sparked/allowed this remarkable transition?
Well, when humans first evolved, the earth was in the middle of an ice age. Average temperatures were ten or fifteen degrees colder than today. It was tough surviving. As glaciers advanced and receded, people had to keep moving to follow the food. Climate change was the norm. About 125,000 years ago or so, earth emerged from the ice age, and temperatures shot up (over about 10,000 years) to about 10 degrees or so warmer than today. Ice melted, seas rose, and life was tough for a whole new set of reasons. It wasn't until about 100,000 years ago that the global temperature settled down to something temperate, but that didn't last long (in the grand scheme of things) before we sank into a new ice age. That ice age continued until about 15,000 years ago. Temperatures rose until about 10,000 years ago.
That's when the magic happened. About 10,000 years ago, the earth warmed up to about the same temperature it is today. And then, until today, it has stayed within about a degree of that temperature. There have been localized warmer and cooler periods, but nothing like what the species had previously experienced. Ice and sea levels have stayed fairly constant. And people have gotten around to creating civilization. Not only did the temperate conditions allow us to fine tune agriculture, the relative stability of the climate has allowed us to focus on things like building cities that require free time and staying in one place for longer periods of time.
That's where we sit today. Human civilization has evolved for the current climate conditions. A few degrees up or down may not seem like much, but look how perfect things had to get before people were able to get their act together. And now, average global temperatures are at the high side of anything we've seen for 10,000, years and likely higher than anything for the past 100,000 years. And they are headed higher.
Civilization was created and has only existed during this current stable climate period. Does that mean civilization will end when the climate changes? Probably not, because we're a whole lot smarter than we were ten millennia ago. But that doesn't mean there won't be huge impacts.
So, next time someone tries to convince you that a rise of a couple degrees is not significant, tell them that human civilization wouldn't exist if temperatures had risen a couple degrees a few thousand years ago.