Now of course there are indeed all kinds of things I can do to reduce my contributions to climate-altering emissions: buying less stuff, ditching the car, cutting flying, purchasing renewable energy, eating less meat and dairy and so on (note that recycling or changing lightbulbs, which are the usual answers people want to hear are way down this list, since they are relatively minor compared to some of the things here).
Personal footprint reductions are good, being: (a) simply the right thing to do in a world throwing away its habitable climate; (b) culture-shaping (normalising solar-installation, for instance); (c) economic communication to corporations (though this influence is plutocratic in effect, since it is one dollar one vote); (d) a talking point for persuasion (people ask questions); (e) an actual (albeit tiny) contribution to global emissions reduction; and (f) important for avoiding the all-too-easy charge of hypocrisy (this is one of the most common lazy defeater arguments people use to keep these issues at bay and it's powerful to be able to show how you're shifting your lifestyle).
But personal footprint reductions are secondary. On the timescales we have and with the structure of the problem locating particular power in massive fossil fuel interests to block progress (through corruption/regulative capture of the political authorities), it is critical that responsible action focus on cultural and political action. If we had a century in which to reduce emissions then personal lifestyle changes and a bottom-up cultural change would undoubtedly be the way to go. If we were not facing one of the richest and most powerful industries in history with a track record of shaping the political landscape to suit its agenda, then building a new and better alternative would be relatively straightforward.
Unfortunately, we don't have decades to start reducing emissions. A significant fraction of our emissions today will still be altering the climate in tens of thousands of years and we're already at the point where the observed changes (let alone those in the pipeline due to the temporal lag between emissions and warming) are becoming increasingly dangerous to human and natural systems. Two degrees warming is flirting with disaster; four degrees is a recipe for catastrophe. Our current trajectory is heading for four degrees or more. Every year we delay, the price tag of the necessary emissions reductions jumps by something like US$500 billion.
We're well past the stage where quietly changing a few lightbulbs is going to cut it.
This is one of the reasons why I am excited about the campaign to get individuals and institutions with a social conscience (churches, universities, city governments) to divest from fossil fuels. Divestment is not primarily an economic strategy, since my few dollars will always be dwarfed by the massive sums and inertia associated with business as usual. Divestment is a cultural and political strategy, changing the nature of what is normal and thinkable (i.e. culture) by putting fossil fuels into the same category as other "unthinkable" ways of making money (e.g. asbestos, tobacco, weapons, gambling, etc.), and in doing so, also changing the way that the political winds are blowing, repositioning the fossil fuel lobby to be as politically toxic (or more) than, say, the tobacco lobby. When politicians are embarrassed to be seen publicly with the fossil fuel lobby, we're winning; when they know they have to stop receiving all donations from them due to the political costs involved, then we've won.
At least round one.