Physics of Climate Change

Lawrence Krauss

Very good. Quick read, dense. Lots of good links in the back too.

Life likely started by harvesting energy from the Earths core, but eventually discovered the sun as a resource, which at the surface, suppiles more than 10e5 the energy of the Earths core.

Respiration is controlled burning. Both breathing and buring combined oxygen with organic compounds to form CO2 Living systems are able to extrace ~30x the energy they would generate by photosynthesis. (Electrons in 02 -> ATP) Physics of Energy

The key to undestaning human impact is that we are able to access – in an extremely short time through our technologies – huge quantities of carbon that tool 10e8 years to build up. This allowed us to usher in modernity. Maybe this is a general observation: Huge reservoirs of easy to use energy prerequirement for advanced civilization ?

Only about half the CO2 we emit ends up in the atmosphere, the other half goes in ocean or in the soil.

1 kw/m2 from the sun at R_earth -> 0.3 kw/m2 when you put in the geometry (pi R² vs 4pi R²)

Solar energy is 1000x the energy used by all of humans.

A subtle, key to the green house effect:

• most of the incident sunlight is absorbed by the earth surface
• most of the outgoing radition is radiated out into space at the top Earths atmosphere (the outer atmosphere is colder and has a higer fraction of c02)

Simple reason why N2 and O2 dont absorb much infrared radiation: While C02 and H20 do… modes of vbiration Bending is slower than vibrating

0—0 vs 0 / \ <—> 0 0 <—>

So N2 and o2 preferentially absorb in the UV (blocking harmful UV rays) H20 and CO2 absorb in the IR

C02 in the air 0.03 % (by volume) of the atmosphere 0.05 % (by weight) => 0.3 mm partial pressure => 0.6 g/ cm² => 1mm over earths surface

Weight be 10e4 kg/ m² ~ 10 tons / m² C02 weights ~ 5e-4 x 1e4 kg/m² ~ 5 kg /m² (5000 g / 10₀₀₀ cm² ~ 0.5 g /cm²)

rho_C ~ rho_W ~ ton/m³ ~ g/cm³ => height inorganic molecules ~ 0.5 cm Estimation

Our climate is sensitive is to changes in the abundance of a molecule whose concentration in the atmosphere is 10e-4, something that naively seems absurd.

Preindustrial carbon in the atmosphere was 600e9 tons… we have added 500e9 tons to date.