What is the best energy engineering profession to help mitigate global warming?

I know climate destabilization is a one of the most pressing global problems today.

In your opinions, what is the best energy engineering profession to help mitigate global warming?

I'm looking for an analytical response, with support.

I am currently studying mechanical engineering because I feel that one of the following would have a great affect of mitigating global warming:

Renewable Energy Company- This would be a company manufacturing renewable energy machinery (wind turbines, solar panels, etc). I'm interested specifically in wind energy. Helping pioneer this field will help renewables begin to replace coal and natural gas, in terms of energy PRODUCTION. I know that renewables are necessary in the future, but I feel that there might fields that have a greater affect.

Energy Services Company (ESCO) - Apparently, half of the energy consumed in the U.S. is from buildings. So making buildings more energy efficient also has a great affect. This is from the CONSUMPTION side, so it would reduce energy consumption (and save companies $), hence reduce energy production and therefore CO2.

Those are the two fields I can think of. But I want to head from others.

I'd like to ask:

1. What are your thoughts of the above two fields (renewables - CLEANER PRODUCTION, ESCO - REDUCING CONSUMPTION) Which do you think has a bigger impact?

2. Are there others fields you can think of?

Thank you!