How betting can clarify wishy-washy positions on global warming

I've been gradually expanding the list of bloggers I've asked to bet over global warming (unsuccessfully so far). There are a fair number who argue global warming might happen but it might not, so let's just try our luck. I think they're hiding behind vagueness, and betting odds could bring out what they really think.

Below is an email I sent to one blog that argues for the "maybe" position. I just sent it, so we'll have to give them a little while to see if there's a reaction.
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Dear John,

I've looked at various posts that your blog, Right
Wing News, has on global warming.  They seem to say
first, that human-caused global warming might be
happening, but we don't really know that for sure, and
second, even if we're causing warming, we shouldn't do
anything to stop it.

I'm not really interested in the second part of your
argument.  The first part is more interesting because
I think it's what a lot of right wingers say as a
justification for passivity.  I want to bet you over
your position on whether global warming is happening.

You might think there's nothing to bet about because
your wishy-washy position could go either way, but
that's not quite right.  I have a number of bets I'm
willing to offer that give up to 2:1 and 3:1 odds in
favor of the side arguing for no warming.  If you
reject those odds, then you can still claim you think
global warming only has a chance of occurring, but the
probability you're assigning to global warming is
high.  At 2:1 odds, you either believe there are at
least even odds that human-caused warming is
happening, or you would want to bet me. So I'm curious
as to what your reaction is.

To see some details on bets, here is a bet I'm
offering to people who believe in "natural" global
warming:

http://backseatdriving.blogspot.com/2005/10/believers-in-natural-global-warming.html

And here are a bunch of others:

http://backseatdriving.blogspot.com/2005_05_01_backseatdriving_archive.html#111700433898143899

I hope to hear from you.