In my experience, one of the most effective ways would be to capture CO2 at large stationary source points (power plants, steel works, cement factories, etc.) and safely store the captured CO2 deep underground in suitable natural storage geological formations. This is known as Carbon Capture and Storage (CCS).

See for example the website of the Global CCS Institute (https://www.globalccsinstitute.com/ ), and particularly this page https://www.globalccsinstitute.com/understanding-ccs

Also, see https://en.wikipedia.org/wiki/Carbon_capture_and_storage

I agree with Dr. Roberto on CCS. I think the basic reasons for the production and release of CO2 to atmosphere are already known, and hence our primary attempts should be how to reduce the emission of CO2. One of the mitigative measures is reduction of burning of fossil fuel, and this can be achieved by reducing the density of vehicles and increasing the efficiency of the public transport system. "Prevention is better than cure".

I agree with Dr Kenneth M Towe,CCS technology is far from working at a global scale.Using carbon capture and storage (also called geosequestration or carbon sequestration) technologies, Only a handful of small-scale demonstration projects are operating. There isn’t a single commercial-scale power plant capturing and storing its emissions. Even projects that have managed to achieve operation, and been heralded as successful, are plagued with problems. The troubled SaskPower coal-fired Boundary Dam project in Canada is just one example. There is no room for fossil fuels in a climate-safe future; the only way forward is to leave these dirty fuels behind. In terms of “effective”, at present Only Solar and renewable seems( although they also have the carbon footprint and emission) the option. In my opinion, at present, the world has option of energy technologies that emit little carbon  (Effective in the true sense) rather than no carbon. 

I agree to Dr Robert. However the technology has to be made available to developing countries as they contribute global warming gases significantly

I agree with Dr Robert. However we have to improve methods of capturing Carbon dioxide