Well, fundamentally that still makes the basic issue CO2, doesn't it? Whether you attack that by reducing emissions, or by planting trees to try and extract more from the atmosphere.
Having said that, your first point is definitely correct. We've spent the last 15-20 years encouraging people to buy diesel-engined cars because of their lower CO2 emissions, without considering all the other stuff that a diesel car kicks out that a petrol one doesn't--especially NOx emissions, which are far more harmful for the local environment than CO2 is even if it's not as big a problem globally.