The guests debated global climate change. Mr. Murray acknowledged global warming exists but doesn’t believe it’s a catastrophic situation. Ms. Callahan believes global warming is indeed a catastrophic situation that needs something done about it now. During his visit to Washington this week, British Prime Minister Tony Blair talked with President Bush about global climate change, suggesting that climate change be made one of the themes of the G8 summit in Scotland next month. They responded to audience telephone calls, faxes, and electronic mail.