The goal is to cut global CO2 emissions in half by 2050 to prevent dangerous global warming. The researchers looked at different technologies and costs to achieve this. They found that a low-carbon energy system would only cost less than 1% more than a high-carbon system. To reach this goal, we need to focus on clean electricity and improving energy efficiency in all sectors. But to keep global warming below 1.5°C, we would need to completely eliminate emissions by 2050, which would require even more effort.