....the Vikings were raising crops in Greenland in the Middle ages?
Economies respond to ALL climate changes. What's new are GLOBAL changes CAUSED by human economic activity.
Enlighten me. How did Midieval human economic activity begin the global warming that enabled crops to be grown in Greenland? (hint: did they have solar power back then?)
Earlier climate variations were a result of natural forces...still only partly understood.
But I look at the environment around modern cities like Los Angeles, Tokyo, Mexico City, and at observable atmospheric pollution in remote places like Grand Canyon, and at the condition of the oceans, and I KNOW that human economic activity can have a local or regional effect. It's therefore easy for me to believe the effect could become global as that activity increases.
That the scientific community increasingly confirms this speculation gives my beliefs solidity.