This is how the world can close the ‘green’ investment gap, according to Al Gore. The world invested a record $1.7 trillion in clean energy in 2023. But this falls far short of what’s needed to keep the energy transition on target. Experts say the world needs to invest $18 trillion by 2030 to limit global warming to 1.5˚C. Here are several ways to ramp up green investment, according to Al Gore.