I've always been a strong supporter of environmental protection and initiatives in that area. But I'm willing to set priorities. If we have to make reductions in one place, we'll have to-in order to increase another place, I'm willing to do that.

The first autonomous cars date back to the late 20th century. But recent increases in sophistication and reductions in cost - reflected, for example, in cheap LIDAR systems, which can 'see' a street in 3D in a way similar to that of the human eye - are now bringing autonomous cars closer to the market.

From solar to electric cars, from geothermal to reconfiguring the grid, the scale of investment needed in green technologies in order to meet whatever agreements on emissions reductions are finally agreed will be immense.

President Obama has offered a plan with 4 trillion dollars in debt reduction over a decade with two and a half dollars of spending reductions for every one dollar of revenue increases and tight controls on future spending. It's the kind of balanced approach proposed by the bipartisan Simpson-Bowles commission.

I've always been a strong supporter of environmental protection and initiatives in that area. But I'm willing to set priorities. If we have to make reductions in one place we'll have to-in order to increase another place I'm willing to do that.