A good parable about global warming:
"We are in a raft, gliding down a river, toward a waterfall. We have a map but are uncertain of our location and hence are unsure of the distance to the waterfall. Some of us are getting nervous and wish to land immediately; others insist we can continue safely for several more hours. A few are enjoying the ride so much that they deny there is any immediate danger although the map clearly shows a waterfall... How do we avoid a disaster ?"
(George S. Philander, "Is the Temperature Rising ?", cited by Brian Fagan in the preface to "The Little Ice Age")