We have an atmosphere that is roughly 21% oxygen. The rest of it is largely nitrogen. There's just enough carbon dioxide (CO2) to drive photosynthesis. That has been, throughout the history of our species, pretty stable. Until recently.

Never before have we known what we know.

The Arctic is a place that historically, during all preceding human history, has largely been an icy realm with an impact on ocean currents. That, in turn, influences the temperature of the planet. The Arctic is now vulnerable because of the excess carbon dioxide in the atmosphere, with a rate of melting that is stunning.

For humans, the Arctic is a harshly inhospitable place, but the conditions there are precisely what polar bears require to survive - and thrive. 'Harsh' to us is 'home' for them. Take away the ice and snow, increase the temperature by even a little, and the realm that makes their lives possible literally melts away.

Ignorance is the biggest problem of all for the ocean - and for many other things as well.

When you are a child you learn your alphabet, your numbers, but increasingly, we must learn from the earliest stages that the highest priority has to be to maintain the world as a safe place for humankind.

We woke up some years ago about the consequences of ozone depletion, the hole in the atmosphere. You can't see it. You can't taste it. You can't smell it. But now we do regard that as a key issue. It's a scientific finding.