I strongly dispute Cohen's claims on available uranium. US government estimates are that there's a ~80 year supply of uranium as a small fraction of present total electrical generation. That falls to 6 years if all global energy is to be supplied from extant uranium reserves. Claims that uranium can be feasibly extracted from seawater are interesting, and though I waive final judgement, I'm not convinced.

I've addressed a 62,000 year supply estimate for thorium. The author makes a massibe substantive underestimation of present total energy consumption. Correcting for this, using his abundance and reserves estimates the supply is good for 42 years: http://redd.it/23nvqs

NB: Thorium is not present in seawater at any appreciable concentration, and the uranium seawater trick doesn't apply.

Climate change and sea level rise are non issues since nuclear power will be widespread before those things cause any problems.

There's a baked-in several-degrees rise already, and a very significant lag in concentrations and climate effects. We'll be seeing the consequences, it's a matter of how much and for how long. I've seen estimates of 300 - 1000 years for the atmospheric CO2 balance to return to preindustrial levels even if all human emissions cease. See: http://www.nature.com/climate/2008/0812/full/climate.2008.12... http://blogs.edf.org/climate411/2008/02/26/ghg_lifetimes/

There's also the problem that a large portion of carbon emissions aren't due to fossil fuel emissions directly: concrete, agriculture, deforestation, and cattle are all sources. As well as other greenhouse gasses, some with higher effects than CO2, some with longer atmospheric residency. It's complicated (and no, I'm not fully versed in specifics). But these will continue to have to be addressed.

Same for topsoil, the nutrients that make it good don't get used up

Topsoil itself is eroding and being washed away. The soils of the great plains have literally decreased, by many feet, since farming and ploughing began in the mid-19th century. Nutrients aren't merely taken up by plants but are then transported off the farmland, to be eaten and dispersed. Added nutrients wash away with irrigation water fouling rivers (don't move along the lower Mississippi if you can help it) and forming offshore dead zones in the Gulf of Mexico, Yellow Sea, and elsewhere, due to algae blooms and oxygen starvation.

You're ... well out of your depth and highly underinformed (or misinformed) on all these points.

Don't forget we can make aviation fuel from energy plus air

I've addressed that multiple times elsewhere on this post. I see seawater rather than air as a CO2 + H2 feedstock as being much more viable. It's still tremendously energy intensive, and my estimate is that replacing present US petroleum consumption would likely cost ~$16 - $24 trillion between the fuel synthesis and energy inputs. I consider that plausible (amortize the costs over 40 years, roughly $2000 per man woman and child at the low end, about 4% of GDP over that period). Assuming the estimates hold.

https://news.ycombinator.com/item?id=7718584

https://news.ycombinator.com/item?id=7719535

Better would be to get carbon from plant waste, hulls, straw, etc.

Bullshit. Not nearly enough biomass: http://globalecology.stanford.edu/DGE/Dukes/Dukes_ClimChange...

Again: you're way out of your depth here. Get educated.