Water and sanitation has not had the same kind of champion that global health, and even education, have had.

When you're working on development issues, optimism is not always based on rational analysis, often it is a moral choice.

We have to find climate-friendly ways of encouraging economic growth. The good news is we think they exist.

If we do not act to curb climate change immediately, we will leave our children and grandchildren an unrecognizable planetIt is the poor, those least responsible for climate change and least able to afford adaptation, who would suffer the most.

Why is it that when it comes to our most cherished social goal [health care], we not only tolerate poor execution, sometimes we even celebrate it?

No matter how good you think you are as a leader, my goodness, the people around you will have all kinds of ideas for how you can get better. So for me, the most fundamental thing about leadership is to have the humility to continue to get feedback and to try to get better - because your job is to try to help everybody else get better.

We need to have a plan equal to the challenge.

Ending poverty and ensuring sustainability are the defining challenges of our time. Energy is central to both of them.