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

[GliderGuider]

4. In a world with static or declining energy demand this might be true

Last edited Wed Oct 9, 2013, 02:14 PM - Edit history (2)

i.e. "any power we get from wind, solar, hydro or geothermal is less co2 released into the atmosphere"

However in a world with rising energy demand the story is more complicated.

We can meet some energy demand by building renewable electrical sources instead of fossil fuels. We can also gain energy efficiency by substituting more-efficient electrical motors for combustion engines for example, or improve the efficiency of using fossil fuels for things like space and process heat.

But these two together will only reduce the amount of CO2 flowing into the atmosphere if the global sum of sum of renewable builds plus efficiency improvements stays ahead of the growing global energy demand.

For example, assume that energy demand grows by 2.2%, pa, which is the recent 30 year trailing average primary energy growth rate. Then assume we can supply 0.4% of it from low-carbon sources like renewables - also the trailing 30 year average growth rate of low carbon sources. Assume we get 0.8% as efficiency improvements - the 20-year trailing average of improvements in the energy intensity of global GDP (this actually requires us to double our current 0.8% rate of improvement that is already doing its job to lower energy consumption). 0.4 + 0.8 - 1.2. We need 2.2%, so we're still short by 1%.

There are only two ways to close that 1% gap: by using more high-carbon energy; or through demand destruction, which requires a restriction in economic activity. So far, the global choice has been to maintain economic activity by closing the demand gap with fossil fuels, because economic activity is seen as a higher priority than addressing climate risk.

to stay even at today’s CO2 emissions of 35 billion tonnes per year, we need to improve our year-over-year efficiency improvements by 50% and triple the growth rate of low-carbon energy rollout. In order to actually start reducing emissions we need to do even better than that – or accept a decline in economic growth, or even global economic stagnation.

It's a herculean task that the world may not be ready for yet, but as you point out, anything is better than nothing.

On edit: The big issue in all this is that for it to work we must somehow constrain economic growth, rather than taking advantage of renewable energy and efficiency improvements to get higher economic growth rates. That is, assuming it always takes some energy to get economic output - which seems more obvious to the ecologically aware than to mainstream economists...

As long as the world holds to the position that growth is a sovereign right of every economy, we are well and truly screwed. Who will (or even can) bell that cat?