In 2003 and 2005, the Senate debated and defeated climate bills mandating GHG reductions sponsored by Senators Joseph Lieberman, then a Democrat and now a Connecticut Independent, and John McCain, then and now an Arizona Republican -- and now also the presumptive Republican presidential nominee. (The 2005 vote was on an amendment attaching the climate bill to energy legislation).

Republicans controlled the Senate in '03 and '05, and the outcome was a foregone conclusion. Democrats control today, by the narrowest of margins, and while the outcome is not necessarily foregone, the legislation will probably fail to garner enough votes (60) to overcome a likely filibuster to block a final vote. And even if the bill did pass and could be reconciled with a bill the US House has yet to draft, the White House announced that President George W. Bush would veto it.

The debate this week will cover well-trod ground. The legislation's proponents will argue, correctly this writer believes, that the evidence is stronger than it was in 2003 and 2005 about the need to sharply reduce GHG emissions, domestically and globally. The opponents will beg to differ, contending that the increase in global temperatures since the start of the Industrial Revolution is part of a natural cycle, bearing little or no relationship to the rapid increase in carbon emissions from the fossil fuel consumption.

This week's debate could be considered a dress rehearsal for the next Congress. It will allow the participants to test their strength, gauge public opinion, and prepare talking points for the fall election campaign. If all the political indicators are correct, the next Congress will be more disposed to passing a strong climate bill. And since the remaining major candidates for the presidency all support mandatory controls on US GHG emissions, the next president should be disposed to sign such a bill.