Honestly, I can be sometimes conflicted both ways. I delve alot more into air quality than most and run the standard air quality models (Mobile & Moves). The scary part about all these models? They really are just best guesses. They base emissions factors and other base data on traffic, travel miles, etc. Thats pretty....not exact. The worst part, these models are ment for regional air quality yet many use them for micro levels (so wrong) and macro country wide, or hemispheric data (very VERY wrong). Some data for GW and GHG (Green House Gas) emissions uses these models on a hemispheric or global scale which most likely produces bad results as these models are calibrated or verified for this use. The global climate models, while a significant step better than the other 2 for hemispheric and global air quality are still using some base data how these more regional models use, thus, it starts to question how accurate these really are.
Scareier still, ask any air quality specialist how Ozone is formed, not basic but the multiple chemical reactions involved with bad air quality to make it. No one knows. Seriously. We don't. We know its a process that takes anywhere from 10-100 different chemcial reactions mixed with the heat of the sun. We know the chemcials invovled, but we have no clue how it gets to the Ozone point. We know so very little, yet we have been studying this for years! GHG emissions are new and there is a similar complex process to create the global warming, but seeing how little we know on stuff thats been problems for years, it really makes me question how much they really know on GHG emissions (btw our base calcluation for GHG emissions: vehicle miles traveled, thats it..so basic).
Now, Carbon Dioxide is the largest HUMAN source GHG emission we know of (there are other minor ones like methane, etc. but they aren't worth mentioning since they take up a small portion), BUT CO2 is NOT the largest GHG emission, not by far. Water Vapor is the largest GHG gas (by far) and is completely out of our control which is why we concentrate on CO2 (#2 behind water vapor) since we control it (something to strain your brain about: if fuel cell cars become mainstream, would the tailpipe emission of water vapor cause an increase in global warming?). So even now, we are concentrating on a gas thats not responsible for most of the regional climate changes we have recorded.
All-in-all we need better facts. Our climate and air quality models are pretty crappy since we don't really understand how it all works. BUT we do know the end results of things like ozone and what chemicals are needed to make that. We do know temperature is increasing (human source? coming ice age?), but we need more hard data (actually more prehistoric data). As a scientist I must concede that the opponents of GW have a point, we don't have enough hard factual data I would be happy betting my results on. From an ecology standpoint of view to say one model and we understand the biosphere AND we know what the problem is is complete arrogance to me. So many studies and "corrections" have been done with animal populations, ecosystems, etc. were we try and introduce or correct something and we mess it up WAY WAY more, from those examples there is absolutely no way we can safely say we understand enough of the entire ecosystem of our biosphere to get these results. There are 7 know really bad mass quanitity polutants the EPA tracks (called NAAQS). Then there are 87 MSAT pollutants that are usually in more smaller quantities but are just as bad. All of these are KNOWN to have health problems associated with them.
In the end I see no need to focus just on GHGs or climate change. Just reduce air pollution period. If we stop carbon monoxide, lead, particulate matter, benzyne, and all the other bad junk, CO2 will reduce too. Why focus on something people question when you can get the same clean-up results focusing on stuff we know is bad.