Virginia should not join RGGI.  This is a Northeastern high-tax high-regulation enterprise and participation in it will damage Virginia's business climate.  Any carbon tax proposal will drive up costs all around. 

This is not an appropriate area for Virginia State action.  This is world environmental policy and should be left to the Federal Government.  .Nor do i accept the argument that "the Federal government isn't doing enough."  Irrespective of one's view as to the issue of CO2 emissions, [atchwork tax and regulatory policies make no sense.  Regulation of outright pollutants at the State level can make sense, because they have localized bad effects.  CO2, however, is a part of the natural cycle and does not hurt anyone; indeed, it actually promotes more plant growth.  Thus CO2 poses no localized health or other environmental risks and should not be regulated, except at the Federal level.  

Indeed, CO2 should not be regulated as a pollutant, because it isn't one.  The issue is whether the rate of worldwide CO2 emissions causes Global Warming (Climate Change is a nonsense phrase, as the climate always changes, while Global Warming is a testable hypothesis).   CO2 should have a different regulatory scheme, since specific, large emissions are harmless; what may be harmful is increasing average emissions.

I fear that you cannot resist the itch to tax and regulate, even though Virginia and even the Northeast is not the proper venue for regulating a environmental issue that is national (actually international in scope.  If you do so, at least the cost of any carbon tax should be returned dollar for dollar to taxpayers in reductions of other taxes and fees.  Since this is going to be very oppressive for motorists, road tolls should be cut and the Car Tax eliminated, using money from the carbon tax to replace these sources of revenue. But, whatever you do, the dollar-for-dollar return of carbon tax to taxpayers and businesses should be the guiding principle.  

Finally, I do not understand how the Executive Branch can impose any carbon tax, as taxation is a legislative function. You can legitimately recommend a carbon tax, but it is usurpation of the legislative brach's proper powers to impose any tax without its passage through the Virginia Legislature.