1. The Carbon Cycle Earth Science 1: Weather and Water July 27, 2010

2. Why is carbon so important? It makes up ~50% (by dry weight) of all living stuff! We are “carbon-based life forms! (“Dammit Jim, I’m a doctor not a bricklayer!!”) CO 2 is necessary for plant growth…without plants, there would be no food! Climate regulation…without CO 2 (and other GHG) in the atmosphere, the Earth would not be inhabitable.

6. Source: http://en.wikipedia.org/wiki/File:Co2-temperature-plot.svg Highest CO 2 level in last 800,000 years.

7. Source: NASA Goddard Space Flight Center How do we know about the climate in the past?

8. Where are we now? Source: USGCRP, Karl et al, 2008  We are already at a level not seen in ~ 1 million years!

9. Where could we be in the future? Source: USGCRP, Karl et al, 2008  And it will only get worse…

10. Global temperature

11. Geological Carbon cycle Movement of carbon during physical processes of weathering, dissolution, precipitation, and tectonics. CO 2 + H 2 O  H 2 CO 3 chemical weathering and dissolution CaCO 3  precipitation, lithification, burial Tectonic uplift eventually exposes buried carbon (i.e., Himalayas) Timeframe: millions of years

12. Biological Carbon cycle Primary producers (those that can create their own food) take inorganic (CO 2 ) and create organic carbon (stuff of life). –Plants remove ~200 billion tons of carbon/year (1.8 X 10 17 gC/year)  Same amount is returned through cell respiration and decay (rate is 1000X faster than geological cycle) –Land use change has created an imbalance Since 1850, 155 PgC (1.55 X 10 17 gC) released from LUC. By 2000, rate = 2 Pg C (2 X 10 15 gC) per year Respiration: C 6 H 12 O 6 + 6O 2  6CO 2 + 6 H 2 O + energyenergy Photosynthesis: energy + 6CO 2 + H 2 O  C 6 H 12 O 6 + 6O 2 energy

13. How are humans changing the global carbon cycle?

14. Petagram (Pg) = 1X10 15 grams 1X10 12 kg

15. Upsetting the natural Carbon cycle. Source: http://www.global-greenhouse-warming.com/global-carbon-cycle.html

16.  Why does the curve go up and down every year? Keeling curve: Charles David Keeling, Scripps Institute

17. Mass balance approach An accounting scheme for any measurable quantity: mass, energy or even cash. (Sum of all inputs) – (sum of all outputs) = Change in storage within the system. Need to define the boundaries of the system Need to specify a time step (usually annual) If system is in balance, then change in storage = 0 … (Sum of all inputs) = (sum of all outputs)

18. Global Carbon Cycle

20. Missing carbon mystery: Case solved? Burgermeister, 2007, Nature Reports Climate Change. (http://www.nature.com/climate/2007/0708/full/climate.2007.35.html)http://www.nature.com/climate/2007/0708/full/climate.2007.35.html - Human Carbon emissions = 8 billion tonnes per year 6.4 tonnes from fossil fuels 1.6 tonnes from tropical deforestation -Of that, 3.2 remains in the atmosphere (observed), 2.2 absorbed by the ocean and 2.6 absorbed by land (mainly forests). -2.4 tonnes of land C modeled to be taken up by northern forests. But observations could only account for 0.7 tonnes C.  Much of what we “know” about the carbon balance is based on Earth system models that simulate land, ocean, atmospheric exchange and fluxes. Turns out 9 of 12 models are wrong about vertical mixing of CO 2.  Tropical forests absorb almost all CO 2 from deforestation.  BUT, NOT A LONG TERM CARBON SINK…residence time ~ 30 yr

21. Carbon Sequestration Researchers are looking for ways to reduce atmospheric carbon by different methods of carbon sequestration –Underground reservoirs –Ocean sequestration Phytoplankton fertilization Direction injection of CO 2 into deep ocean. –Enhance terrestrial cycle

22. Land Management to sequester carbon LUC has emitted Gt of carbon Proper forest management could reverse this to a degree Depends on CC not accelerating enough to kill forests!