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Sources and Sinks Climate Change Carbon Fossil fuels are not naturally a part of the fast cycle: every ton emitted changes the carbon cycle for thousands.

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Presentation on theme: "Sources and Sinks Climate Change Carbon Fossil fuels are not naturally a part of the fast cycle: every ton emitted changes the carbon cycle for thousands."— Presentation transcript:

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2 Sources and Sinks Climate Change Carbon

3 Fossil fuels are not naturally a part of the fast cycle: every ton emitted changes the carbon cycle for thousands of years

4 Carbon Sources and Sinks Places that provide carbon are called reservoirs. Places where carbon settles are called sinks Exchanges between sinks and reservoirs are called fluxes. There are four major reservoirs for carbon The atmosphere The oceans The biosphere Fossil fuels Ultimately the crust forms the basic sink for carbon via the deep oceans to carbonate rock and fossil fuels

5 Carbon Sink This model shows the main carbon pools on Earth, limited to those that can exchange significant amounts of carbon in the short term (lime is thus not shown, though it constitutes the largest stock of carbon on Earth). Figures are in gigatonnes of carbon (GtC).

6 Carbon Sink  Flows in black represent the "natural" exchanges, those that existed in 1750, before the beginning of our industrial activities and pool figures in black represent the amount of carbon stored in  Flows in red represent the human direct or indirect average contribution for the 1990's, and stock figures in red represent the net effect of human activities from 1750 to 1994.

7 What It Means This diagram means, among other things Ocean sediments at the top of the ocean floor contain 150 billion metric tons of carbon, an amount that has not changed since the beginning of the industrial era The intermediate and deep ocean contained billion metric tons of carbon in 1750, an amount that went up 100 billion metric tons since the beginning of the industrial era Terrestrial ecosystems contained 2300 billion metric tons of carbon in 1750 (in the vegetation, soil and humus), an amount that went up 101 billion metric tons since the beginning of the industrial era because photosynthesis continuously increased since then, but in the same time went down 140 billion metric tons because of forest clearing

8 What it Means The atmosphere contained 597 billion metric tons of carbon in 1750, an amount that went up 165 billion metric tons since the beginning of the industrial era because of our CO2 emissions. The overall extractible fossil fuel reserves (oil, gas and coal, totaled 3700 billion metric tons of carbon in before we began to dig in it - and that at the end of 1994 we had extracted (and burnt, with CO2 going into the air) about 244 billion metric tons (note that between 1994 and 2005 this figure has risen by 30%).

9 The Carbon Cycle with and without humans  In 1750, WITHOUT industry & vehicles, there was around 280 CO 2 molecules in every million air molecules  In 2010, WITH industry & vehicles, there is now 389 CO 2 molecules in every million air molecules (35% increase) Plants Animals Industry & Vehicles Organic Material Fossil Fuels Atmosphere Photosynthesis Respiration Decomposition Burning Pumping Plants Animals Organic Material Atmosphere Respiration Decomposition Photosynthesis Fossil Fuels

10 Greenhouse Gas Concentrations Compared to natural changes over the past 10,000 years, the spike in concentrations of CO 2 & CH 4 in the past 250 years is extraordinary. Humans are responsible for the recent dramatic increase emissions. Fossil CO 2 & CH 4 lack carbon-14, and the observed drop in atmospheric C-14 is measurable. (IPCC AR4 WG1, 2007)

11 Greenhouse Gas Concentrations These figures show Atmospheric concentrations of the key anthropogenic greenhouse gases were constant over hundreds of years until the industrial era. Observed increases of 33%, more than a factor of two. About15% are attributable to human activities.

12 Greenhouse Gas Concentrations Similarly, the atmospheric concentration of sulfate aerosols started to increase in the late 1800s due to the combustion of coal.

13 Greenhouse Gases: CO 2 The most plentiful greenhouse gas Results from Combustion of fossil fuels Gas (best) Oil (medium) Coal (worst) Based on ratio of carbon to hydrogen in the molecules Burning of vegetation/deforestation Reduced uptake in plants/deforestation

14 Greenhouse Gases Methane  Methane concentrations have increased 2.5-fold since 1750  Sources  Coal mining  Oil production  Organic decomposition in landfills  Animal digestion (feedlots)  growing more crops such as rice to feed the world’s increasing human population  Resident in atmosphere about 10 years

15 Nitrous Oxide and Tropospheric Ozone  Anthropogenic Increase

16 Anthropogenic Aerosols Particulate matter  Scatter sunlight back to space  Cause more, smaller cloud particles (increase albedo)

17 Chlorofluorocarbons (CFCs) Nasty little gases – only anthropogenic CFCs do not occur in nature – the Fluorine bond is too strong to break naturally. CFCs come from Refrigerants Styrofoam, foaming agents Cleaning electronics Spray propellants

18 Global Warming Potentials CO 2 is the most abundant greenhouse gas in the atmosphere, it contributes more to the natural and to the anthropogenic greenhouse effect. According to latest data, CO 2 is exerting nearly six times more impact than methane, nitrous oxide, and halocarbons combined Methane holds more heat, but because it is chemically more active, its atmospheric duration is about 10 years

19 Radiative Forcing  The amount of change in thermal energy that a given factor causes  1.6 watts/m 2 (thermal energy) above what it was 250 years ago  I.E. the planet is receiving and retaining 1.6 watts/m 2 more thermal energy than it is emitting back into space.


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