Vaclav Smic is a world leading authority on energy systems and usage. I had the fortune to hear him speak at a CLSA event this week.

See his work and academic credentials here.  His books give more data and insights. These two pieces on energy here (2017 Annual Energy paper with JPM) and here, (A skeptics look at alternative energy) also expand on these notes below in more detail. Bill Gates is a fan. 

My brief impressions are:

We are heading for >2 degree world. Too much is already baked into the pipeline. I] It is unlikely we will bend human behaviour enough by 2050. Energy transitions as can be seen throughout history take a long time (decades).

We need to be prepared to deal with negative catastrophes in places like Bangladesh and Florida. Conversely, it is possible that much of Russia will benefit. One could argue Russia might want to ensure at least a +3 degree warm happens if it was only self interested.

We should think about consuming less. The impact of eating 50 percent less beef in the Developed world would be significant. Turning vegetarian for one day a week could also be very significant in terms of carbon impact.

Smil views improving battery technology as incremental. He cites 100 years of progress since Edison made an improvement. He does not view mass efficient energy storage of the type needed to power a city for one day as likely to come on to the market in the next 20 years. He cites near term the biggest to be completed in 2021 in California as being insufficient to power most cities for more than a few hours.

Smic is optimistic on the impact that moving to natural gas could have. Both in terms of pollution, but also in terms of efficiency. Gas is still FF though.

There are no viable alternatives for producing fertiliser, steel, plastics, and much of the basic materials of the modern world; and flying planes other than fossil fuel use. This leaves likely FF to make up at least 50 percent of worlds energy requirements on an ongoing basis.

Fusion. Commercially - The most optimistic assessment would be "Not in our life time" or perhaps "Never". He cites two world fusion experts.

Cities don't really sleep. However solar and wind in most places are not reliable. This is why even though Germany which now has renewable capacity to match its fossil fuel capacity has not impacted meaningfully its FF use, not its carbon emissions from Energy use.

In many places in the world the grid is not connected. One can't send energy from San Francisco to Texas. Or from Texas to Canada. In some places it can work, Denmark can obtain hydroelectric power from Norway when the wind is not blowing. Few people want high energy transmission lines traversing their backyard or landscape, so the situation is unlikely to rapidly improve.

In discussion, as an aside - We will cure more cancers before we solve the mass electricity storage problems  (I happen to agree with this view on the cancer side, I'll have to rely on Smil on the storage problem)

The return on vaccines is at least 44x.  Eradicating polio has been an amazing world benefit. As an advisor to Bill Gates, this is not a surprise to have this view. The Gates foundation has worked on this for a while now.  Many world human development metrics have vastly improved over the last 25 years (As my infant mortality post shows as well, hopefully more data on this).  You can see the Gates work here and a Smil article on it here.