"It is not a substitute for cutting emissions — it is a supplement. We can't keep using the atmosphere as a waste dump for carbon and expect to have good climate, no matter what we do to reflect away some sunlight."

"Over decades, Canadian governments have emasculated or killed institutions that gave independent advice on science and technology so that they are now among the weakest in the G7. Federal and provincial governments increasingly demand that research funding be tied to matching money from industry, so work that threatens industry's interests does not get funded. It's a good idea to tie some applied work in engineering to industrial interests, but this requirement must not apply to policy analysis."

High cost and technical immaturity of bulk (multi-hour) electricity storage (BES) systems are often cited as major hurdles to increasing the penetration of intermittent renewables. The authors use a simple model to assess the economics of BES under carbon emissions constraints.

HEA: You have conducted research on whether patents on solar geoengineering technologies could be banned and advocated for keeping these technologies in the public domain. What are the dangers of privatizing solar geoengineering?

Keith: With incredible technologies like this, you could destroy the world. You don't want private enterprise making nuclear weapons, and you don't want that with geoengineering. The decisions could impact the whole world and need to be taken as legitimately and as transparently as possible....

"...[A]ttention is turning to solar geoengineering, also known as solar radiation management. Although the concept of injecting sulfur dioxide into the stratosphere has so far been tested only using computer simulations, there's high confidence that it would work to cool the Earth because it would mimic the well-understood cooling effect of large volcanic eruptions."

Solar engineering and other exceptionally ambitious new technologies to deal with the reality of rising global temperatures come riddled with uncertainties. To illustrate how complex the problem is and what kind of challenges lie ahead, here are three contrasting, and somewhat fantastical, scenarios.