Earth’s Surface Temperature Sans Atmosphere

• T = (S* (1-a) / r2 / 4 / SB)1/4

– S is the solar constant in Watts m-2 ~ 1367• The actual direct solar irradiance at the top of the atmosphere

fluctuates by about 6.9% during a year due to the Earth's varying distance from the Sun

• 1.412 kW/m² in early January • 1.321 kW/m² in early July a is Earth’s albedo ~ 30%

– r is the average Earth-Sun distance = 1 AU– SB is Stefan-Boltzmann's constant = 5.67e-08

• The result is 254.86 K – what is that in Celsius? -18°C– In Fahrenheit? 0°F

Atmospheric CO2 concentration isnow nearly 100 ppmv higher, and has risen tothat level at a rate at least 10 and possibly 100times faster than at any other time in the past420,000 years. We have driven the Earthsystem from the tightly bounded domain ofglacial-interglacial dynamics.

Deuterium is used widely as a tracer for analyzing chemical reactions, and it combines with oxygen to form heavy water. Also called  heavy hydrogen 

Terminology• DIC• Solubility pump• Biological pump• Sink vs. Source

• Dissolved inorganic carbon, related to pH levels. CO2 is soluble in water, reacting to created ionic and non-ionic species (e.g. carbonate CO3

2-)

• Physical-Chemical transport of carbon from the ocean’s surface to deep water. Driven by sea temperature (colder>>more soluble) and THC.

• Biological transport of carbon from surface to deep ocean waters. Organic or PIC (CaCO3) from calcifying species (coccolithophores)

• What are the 2 major recurrent questions?– Can we distinguish between anthropogenic and natural

biogeochemical cycles– What is the sensitivity of Earth’s climate to changes in

atmospheric CO2• What does ice core data tell us?

– CO2 oscillated in 100K year cycles between 180 and 280 ppm

– On millennial time scales – CO2 highly correlated with Temp changes

– *Although temps may change abruptly without a discernable change in CO2 – the opposite is not true

• i.e. IF CO2 changes >> Temp will to– How are CO2 records inferred?

• Ice cores and fossilized shells use the ratio of isotopic oxygen-16 (light) and 18 (heavy)

• Less heavy oxygen in ice cores means temperatures were colder

• The active carbon reservoirs and their strengths. – Atmospheric CO2 exchanges rapidly with oceans and terrestrial ecosystems– The remarkable consistency of the upper and lower limits of the glacial-

interglacial atmospheric CO2 concentrations, and the apparent fine control over periods of many thousands of years around those limits, suggest strong feedbacks that constrain the sink strengths in both oceans and terrestrial ecosystems.

– The rates of absorption and emission of CO2 from the oceans and terrestrial ecosystems are asymmetrical.

• Because of this asymmetry – average CO2 atmospheric concentrations of the past was only 220ppm,not 280 (pre-industrial value often cited).

• How is atmospheric CO2 regulated?– Total DIC in the oceans is 50x that of the atmosphere– Land than Ocean? 3x– Millennial time scales oceans determine atm. CO2 concentrations, not vice-

versa• Why is ocean uptake finite?

– CO2 dissolves in water > forming a weak acid– Reacts with carbonate anions CO3

2- and H20 to form bicarbonate (HCO3-)

** Requires additional cations from slow weathering of rocks

• The higher concentration of DIC in the ocean interior (below 300m) is a result of two processes:– The Solubility Pump

• Efficacy depends on the THC

– The Biological PumpCO2 concentrations, and the apparent fine control over periods of many thousands of years around those limits, suggest strong feedbacks that constrain the sink strengths in both oceans and terrestrial ecosystems.

During El Niño, the trade winds weakenalong the equator as atmospheric pressure rises in the western Pacific and falls in the eastern Pacific.

Anomalous warming in the central andeastern Pacific ensues as warm water in the western Pacific migrates eastward and upwelling is reduced

The trade winds normally pile up warm surface water in the western Pacific while upwelling colder water in the east from below the surface along the equator and off the west coast of South America.