Editor's note: Hans Rosling is a professor of international health at Karolinska Institute in Stockholm, Sweden. He was on CNN's GPS in March showing the rise of the rest. Rosling co-founded Gapminder, a nonprofit organization that turns numbers into animations to help make sense of the world.
By Hans Rosling, Special to CNN
I was only 4 years old when I saw my mother load a washing machine for the very first time in her life. That was a great day for my mother.
My mother and father had been saving money for years to be able to buy that machine. And the first day it was going to be used, even Grandma was invited to see the machine. Grandma was even more excited. Throughout her life she had been heating water with firewood, and she had hand-washed laundry for seven children. And now she was going to watch electricity do that work.
My mother carefully opened the door, and she loaded the laundry into the machine. And then, when she closed the door, Grandma said, "No, no, no, no. Let me, let me push the button." And Grandma pushed the button, and she said, "Oh, fantastic. I want to see this. Give me a chair."
And she sat down in front of the machine and watched the entire washing program. She was mesmerized.
To my grandmother, the washing machine was a miracle - as it would be to billions of people around the world today.
There is a direct link between the washing machine and the greatest problems we face.
When I get concerned about the high probability of a world climate crisis, I start to count. There are now 7 billion people in the world.
The number of children per woman has been declining fast over the last decades. Today the world average fertility rate is 2.5 children per woman. A fast decline in fertility has meant that the growth in the number of births each year came to an end around 1990.
In the last 20 years, the number of babies born per year has hovered around 135 million. This means that the number of children in the world - the world population below age 15 - stopped growing some years ago.
There are now about 2 billion children in the world, and future population growth will not consist of children. It will consist of adults and old people. In fact it is people like me, those over 60, who are the fastest growing part of the population of the world.
But the growth of the world's population is predicted to end some years after midcentury at about 9 billion. In other words, that will come within a lifetime after the number of children stopped increasing, and there is not much we can do about that braking distance.
But how is it possible that the world is heading for zero population growth, I hear you saying, when there are still 5 to 6 children born per woman among the poorest in Africa? The answer: that is fully compensated for by the fact that there are fewer than 2 children being born per woman in large parts of Europe and Asia.
So the real climate challenge is not about the number of people, it is about more effective use of energy and more green ways to produce the energy we are going to use. Population growth may only add an extra 30% to the number of people, but most of the 7 billion people on Earth today want a better life - and that means a life that consumes more energy.
That implies an increase in energy use by severalfold more than 30%, and that is where the focus must be if we are to solve our energy and climate problems.
At this point the debate gets wild about what level of wealth we need for a good life. My Talk at TED Women was a concrete argument in that debate.
My argument is that the level of wealth that everyone aspires to will include the washing machine - which 5 billion people still do not have. The proof is that even the hard-core members of the green movement use it to wash their clothes.
And the magic with the washing machine is not only that it saves the skin on our knuckles - it also saves us so much time to do more interesting things, such as reading books and watching TED videos!
The opinions expressed in this commentary are solely those of Hans Rosling.