I am no expert on this but this is always such a touchy topic and mine is usually always an unpopular opinion on it. I really liked how @Myrko articulated what he believes.
4x4s in the desert - may qualify as an environmentally irresponsible hobby - but it is a recreational activity i willingly sign up for every weekend. I can't own a 4x4 and feel guilty for owning one.
So much of our personal carbon footprint is beyond our control (the building we live in and the energy it uses, gps via satellites we use which were put up in space by rockets, construction of the roads we use everyday, the military planes that our government uses - they burn at least 2-3X the fuel used by commercial aircrafts, and a popular president used them for a deportation exercises). The CO2 due to our personal fuel consumption is very negligible when put together in context with everything else.
One must feel good about reducing their fossil fuel consumption, no doubt about that. But one mustn't be bogged down if their cars burn more fuel than the other. Not contributing to the CO2 already there in the atmosphere is as good as not adding galons of water you stored into the ocean (exaggerated).
i consider climate change, carbon footprint very different from sustainability. Again - i am no expert on the topic - this is just my opinion.
My views on the CO2 situation are kinda skewed but i am all for preserving what we have. It disturbs me when i notice plastics or construction debris dumped in the desert - i cuss when i see them. I agree with @Mike M.'s purposeful drive idea - it will add to a sense of fulfilment/accomplishment to the drives. That can definitely be a means to add a sense of environmental responsibility to our otherwise environmentally irresponsible hobby.