Go "hand-in" to touch a shark, a crab, or thousands of tiny cleaner fish that will bite playfully at your fingers.

When we start to have a sense of offering a helping hand for a cleaner city and greener world, and when we have a loving heart to think more of others than of ourselves and are ready to help them, we can say that we have grown up.

To solve these problems, it helps to have two instruments to hand: a carbon tax to discourage pollution directly, and subsidies or other incentives to encourage innovation around the cleaner input.