An interesting laying-out of the costs to produce various scenarios:
- If we keep things as they are, we're likely to face a 6 degrees Celsius rise in average global temperature. This would end life as we know it.
- If we invest $4.1 trillion in energy-related infrastructure and equipment, we're likely to improve our energy efficiency, save $7 trillion, and stabilise greenhouse gases at 550 parts per million in the atmosphere (a rise of about 3 degrees Celsius). This would make life very uncomfortable, and could still trigger run-away heating.
- If we invest $9.3 trillion (and have 36% of the global energy mix by 2030 be low-carbon), fuel savings will only be $5.8 trillion, but we could limit the world to a 2 degree rise in temperature.
The "common sense" option (going for 3 degrees, getting a net saving of nearly $3 trillion) shows why we can't evaluate economic options in the same old way.