Global warming can be easily mitigated at relatively low cost using mirrors on the surface of Earth

It is a bad approach/solution though, because it does not solve the cause of a problem. There numerous other solutions such as CO2 removal from atmosphere.


Simply reduce the temperature of air and produce global cooling by installing large mirrors to reflect the visible spectrum of light (in contrast to IR radiation which is absorbed by greenhouse gases in atmosphere) from the surface of Earth.



Below the primitive first principles calculation explains it all.

At 300K, specific heat of air ~ 1 - 0.7 kJ/K/kg. Mass of Earth's atmosphere ~ 5e18 kg.

To cool down all Earth's atmosphere by 1 degree K (or C), we need to remove this amount of energy from air: 5e18 * 1e3 * 1 [kg * J/kg/K * K] = 5e21 J.

Solar power provides ~ 1000 W/m2 on the surface of Earth, on average 10 hours per day (24 hours).
Then the energy reaching the m2 surface on Earth per year is 1000 * 60*60*10*365 = 1.31e10 J/m2.

If we reflect all sunlight with mirrors back into space, assuming near 100% efficiency,
we need 5e21 / 1.31e10 [J / J/m2] = 3.82e11 m2 of area,  which is equivalent to 6e5 x 6e5 m or ~ 1000 km x 1000 km large mirror.

Assuming mirror costs as $10 /m2, the cost to install such a large mirror is ~ $3e12 or 3 trillion dollars.

As of 2019, US GDP is $21 trillion, Worlds total is $87 trillion.

Global warming problem could be solved in a year with 14% of a yearly US budget or 3% of a yearly Worlds budget!

Note, world spends a of 2 % of total GDP per year on military:
https://en.wikipedia.org/wiki/List_of_countries_by_military_expenditures