With ice cores, we have an Antarctic temperature history going back 400,000 years. <a href="https:&#x2F;&#x2F;upload.wikimedia.org&#x2F;wikipedia&#x2F;commons&#x2F;c&#x2F;c2&#x2F;Vostok-ice-core-petit.png" rel="nofollow">https:&#x2F;&#x2F;upload.wikimedia.org&#x2F;wikipedia&#x2F;commons&#x2F;c&#x2F;c2&#x2F;Vostok-i...</a><p>These ice cores show sudden, massive ice ages every 100,000 years. We are currently near (or overdue for) one of the big ice ages.<p>In such a case it would seem that a warm world, even with a higher sea level and the human movement that would require, would be less disruptive than much of current civilization  being under 200 feet of ice.