Global warning

Time Magazine has a relatively alarmist cover story on global warming this week.

Global warming is a scientific question which has turned into a political question. It sharply divides Democrats and Republicans.

One problem is that there are really three separate issues concerning global warming, and they are often glommed together as one issue.

Specifically:

1. Is global warming occuring? Is there a general global trend of increasing temperatures, and if so, how recent is it?

2. Is global warming caused by or influenced in any way by the activities of humankind or is it a purely natural phenomenon that is the latest in the planet's long history of climate shifts?

3. If global warming is casued by mankind (or even if it isn't) is there anything that we as a civilization can realistically do to arrest or reverse the current climactic trends on a worldwide basis?

I don't know the answer to any of these questions, although my (amateur) opinion is probably "yes" to question one, "maybe" to question two, and "probably not much" to question three.