This is a 50 year goal, and we don't know what technological innovations will happen in the next few years to help towards the goal.
Look at a typical family car as an example, since the introduction a catalytic converters the emissions have dropped dramatically, and fuel economy has risen as well. My 1980 Mini would struggle to achieve more than 30mpg (I used to average around 220 miles out of the 7 gallon tank, I once completely ran out of fuel with 225 on the trip counter) but a new Mini with a bigger, more powerful engine easily gets more than 50 to the gallon.
Similar systems are soon to be fitted to Power Station chimneys to capture the CO2 and filter it out for disposal.
Jet engines are gradually becoming more economical, the A380 uses less fuel than a Boeing 747 (8.7 US gallons per mile as opposed to 10.6 US gallons per mile).
But the biggest factor in the reduction of carbon emissions will be when we run out of oil...