The two scenarios have some things in common: the idea of a world population at nine billion by 2050, increased prosperity and global energy demand. Given those situations, what's the world going to come to? No one knows for sure, but here are Shell's guesses, in short:
"Mountains" implies "a strong role for government" that is not afraid to implement "far-reaching policy measures." These measures mean that cities will develop in more compact ways and "new policies unlock plentiful natural gas resources – making it the largest global energy source by the 2030s – and accelerate carbon capture and storage technology, supporting a cleaner energy system." That sounds like it has some potential, but the problem is that, "nevertheless, the global average temperature rise overshoots the current 2°C goal."
"Oceans," on the other hand takes place in "a more prosperous and volatile world." This is the scenario where solar overtakes natural gas as the world's largest energy source as "power is more widely distributed and governments take longer to agree major decisions." Oil and coal power stick around, but they're slowly replaced by renewable energy. This, too, isn't an ideal solution, since "these measures are not sufficient to address environmental concerns, as greenhouse gas emissions follow a pathway towards a high degree of climate change."
You can get the full 48-page PDF here and see a short video below. A key prediction comes on page 20, in a section called "A Changing Transportation Infrastructure." The long-term view is that:
2070 is a looooong way away, and we're not going to put money on Shell's predictions quite yet. It's still interesting to think about, though, and we'd like to hear your views in the Comments.
By 2070, the passenger road market could be nearly oil-free and towards the end of the century an extensive hydrogen infrastructure rollout displaces oil demand for long haul and heavy loads. By this time, electricity and hydrogen may dominate, and affordable, plug-in, hybrid hydrogen vehicles offer the ultimate in flexibility and efficiency.