The Viability of Germany’s Energiewende: Mark Jacobson Answers 3 Questions

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30. I know that's the renewable dream, and that RMI are the head dreamers.

One scenario (not the only one, just a representative one) that I find more believable goes like this:

Assumptions:

• Oil supply peaks in 15 years, and over the next 30 years oil consumption is approximately flat at today's value.
  
• The shortfall in oil supply of about 30% by 2040 is filled by electric cars.
  
• Gas and coal consumption rise due to increasing wealth (GDP/capita) and population growth.
  
• Coal use is suppressed by about 15% globally due to wind and solar coming on line. .
  
• Gas consumption continues its current straight-line growth, rising by 50% by 2040.
  
• Coal use increases on an approximately straight line, but at a lower slope than today, rising by 35%.

Results:

• Carbon emissions rise by 25% from 34 mt/yr today to 42 mt/yr in 2040, driving CO2 levels to about 475 ppm.
  
• Methane feedbacks kick in seriously in about 10 years, raising the CO2e to 525 ppm in 2040, just short of the IPCC RCP8.5 value.
  
• Rising CO2e gives a global average surface warming of about 1.5C in 2040
  
• That temperature rise begins to break down tropical and sub-tropical societies as their large cities lose social cohesion.
  
• Global carbon emissions level out by 2050 due to social breakdown
  
• We hit 2100 just short of the RCP8.5 value, at about +4C.
  
• Global civilization loses its cohesion and begins to fragment under multiple stresses around 2075.
  
• The fragmentation of global civilization is complete by 2100.
  
• Despite that fragmentation, CO2e and temperature continue to rise due to the methane feedbacks that were triggered over 50 years before.
  
• Humanity enters a Toba-style bottleneck some time in the first half of the 22nd century.

Again, this is not the only possible scenario, but is representative of my thinking. IMO this scenario is somewhat conservative, depending on the strength of the CH4 feedbacks. It is one realistic possibility, that is in line with IPCC projections.

I simply don't believe the RMI fantasies.