I have *not* studied the thermodynamics of green energy or even of conventional energy generation, for that matter.
However, I believe I have a pretty good understanding both of basic science and of our planet.
Earth's surface is roughly 70% water and 30% land. Not all of the land is habitable, even with 6 billion (!) people pushing into marginally habitable regions.
So let's say that roughly 25% of the Earth's surface is habitable (in other words, 5/6 of the land). (Keep in mind large, uninhabitable--or barely habitable-- landforms like the Sahara Desert, the Empty Quarter of Saudi Arabia, the Gobi Desert, Siberia, the Northwest Territories, northern Greenland, the Deccan, the Hindu Kush, most of the Himalayas, the Kalahari, the Outback, and Antarctica.) 25% is no doubt wildly off, but I'm pretty sure it's higher than what it should be, and it will therefore act conservatively in what follows.
Of this 25% of the planet that's habitable, how much *actual surface area* will be devoted to solar energy collectors in the future that your interlocutor was conjuring? By "solar energy collectors," I mean panels, solar ovens, passive water heaters, double-pane windows with seasonally appropriate reflectors/pass-through filters...anything which converts solar energy into a more useable form for the benefit of people or their animals. Plants don't need our help converting solar energy; they've been doing it for millions of years.
I'll wait while minds, calculators, and spreadsheets do their thing.
[tick tick tick
OK. Got it?
75% of the Earth's surface will NOT be affected in any way by solar energy collectors, since this 70% ocean + 5% uninhabitable land is by definition unsuitable for development.
We already experience a large "bounce-back" of solar energy every day due to perfectly normal cloud formations. What will differentiate the bounce-back of solar collectors from that of cloud formations, which are orders of magnitude larger?
Just some questions to ask your conversation partner. Also ask him/her where the information s/he's coming up with came from. It sounds very alarmist as well as perhaps non-scientifically based. I myself would welcome sound science on this point.
Sunset Zone 17, USDA Zone 9