Global Warming: Ice Caps and the Argument from Authority. Why should we trust a PhD in climate science when he talks about ice caps any more than we trust a D.Phil. in theology when he talks about God? Both are experts, but both entered their vocations because they had policy views on their subjects. (Click here to read more.)

This makes it hard to figure out the science on global warming, of course. Here's an example. If there is global warming, will sea levels rise?

Sea levels might rise because the warmth will melt the ice near the North Pole. Also, if sea water is warmer, it will expand, even if there is no more of it.

Sea levels might fall because the warmth and the extra water in the air will increase snowfall near the South Pole, where most of the ice in the world is. Also, there will be more water in the atmosphere instead of in the ocean.

Which is the bigger effect?