Let’s keep it simple to start with: you’ll be richer, have more friends, be happier and get more sex.
You’ll be richer because you’ll be paying less in energy bills around your home, spending less filling your car up with fuel (if you take the diesel or hi-efficiency option), wasting less on inefficient and unnecessary consumer goods (or cheap tat, as we call it here) and paying less for the local council to take away your rubbish or clear up the streets. There are other financial benefits if you run a company, including increased profitability through efficiency gains, lower BTL costs and greater client sympathy.
You’ll have more friends, especially if you are a young adult or someone in the prime of their life, as for the first, the idealism of being serious about the environment as a whole and the climate is now more usual than being sceptical about it. You’ll have something in common to discuss with people, making you more interesting, and you won’t sound like a cynical g*t, which is increasingly becoming the fate of people who pooh-pooh climate change or demonstrate innate scepticism.
You’ll be happier because you’ll know that, even if it did turn out to be less of a problem than most scientists seem to think, you won’t at least have made the world a worse place for your presence. Right or wrong, you’ll feel as if some of the decisions you make about your life have a basis in moral purpose, which implies your desire to be a good person, which in turn makes you feel good about yourself. You’ll also be aware that you are being altruistic in an enlightened-self-interested sort of way, especially if you have children or grandchildren, as you’ll be doing something for someone else. Even if it involves minimal effort and costs you next to nothing (see above), you’ll still feel good about caring about the fate of others and being unselfish. This extends further if you look at the places where climate change is really going to be a problem. You’ll also enjoy the countryside more, being aware that you are interacting with it positively, which may help prevent that nagging feeling that you’d better enjoy it now, before it all goes to hell, that ennui which so often accompanies being out and about in pleasant places.
You’ll get more sex because all of the above will make you inherently more attractive to others. Some of these others will respond in a way which may lead you to satisfy your carnal cravings, should that be your desire. Though it is true that some people find self-important, cynical, self-centred g*ts attractive in a perverse way, more people are attracted to happy, caring people who have a bit of spare cash to spend as circumstances offer. More contentment in yourself easily extends into a confidence and ease which is often compellingly attractive.
Slightly more seriously, by actually doing something to contribute to reducing our energy consumption or increasing our efficiency, you’ll be sending a clear signal to government that you care enough about the issue to do something yourself, so they’d better get off their a*ses and do something, otherwise they won’t get elected next time.
Why “do your bit”? Everyone wins, especially you. Nobody gets hurt. Political commitment becomes more likely. The world becomes a better place.
A much, much more difficult question to answer would be: “why not?”.