Terms of Use: The author of this slide presentations, Andrea Fassbender, requests that anyone who uses these slides please retain all the citations and all the notes for each slide.

the greenhouse effect GHG GHG Sunlight heats the earth surface The Earth surface emits heat to the atmosphere Greenhouse gases absorb outgoing, infrared energy and re-emit that energy in all directions The Earth surface warms more than if there were no GHGs in the atmosphere Incoming solar energy (shortwave) GHGs interact w/ outgoing energy (longwave) GHG Some energy is absorbed and re-emitted GHG 59F with atmosphere, 0F without. Greenhouse gases are molecules that exist in our atmosphere that can trap infrared light. CO2 is an example of a greenhouse gas. When sunlight enters Earth’s atmosphere, most of it is in the high energy- ultraviolet spectrum and passes through our atmosphere easily until it hits Earth’s surface. When sunlight hits Earth’s surface, part of it is released back out as lower energy- infrared light. Earth “radiates” the sunlight that hits it back out as heat and energy. Greenhouse gases are able to trap some of that reemitted, infrared energy, the heat, and keep it here on Earth before it escapes to outer space. Without greenhouse gases in our atmosphere, Earth would be MUCH colder than it is today. It is because of the greenhouse gases that the average temperature on Earth is a comfortable 55 degrees F. Greenhouse gases provide a “blanket” for Earth to keep us warm. Slide from Andrea Fassbender

the long term carbon cycle Continental weathering of silicate and carbonate rocks Volcanism http://ocean.mit.edu Most of the carbon on the planet is inactive, i.e. does not interact with the atmosphere on these short time scales. This inactive carbon is stored in soils, rocks, fossil sediments and deep ocean sediments. These carbon reservoirs interact with the atmosphere on million year time scales. To really understand how humans are impacting the carbon cycle we have to consider both the short term and the long term carbon cycles on earth. Silicate and carbonate rock contributions: CaCO3 rocks + 1 CO2 from atm = 2 HCO3- SiO2 rocks + 1 CO2 from atm = 1 HCO3- Weather atmospheric CO2 by 2, and carbonate rocks by 1. Glacial-Interglacial cycles over the past 800,000 years (where we have ice core records of atmospheric composition and proxies for temperature and ice volume) are widely accepted to be forced by Milankovic orbital forcing. The effects of changing the earth’s distance from the sun, earth’s axial precession, and earth’s tilt axis causes a redistribution of sunlight received on Earth. This is believed to have led to cooler summers during which accumulated snowfall did not fully melt, resulting in continued ice/snow build up in the preceding winter. There is some debate as to whether this alone could trigger the ice age, or if there were CO2 related feedbacks that helped push the earth into the ice age. Deep sea burial of calcium carbonate (CaCO3) and organic carbon Tectonic plate subduction

long term steady state Inflow = Outflow Mount St. Helens Robert Krimmel, USGS Mount St. Helens Carbon returned to the inactive carbon reservoir via carbon burial and plate tectonics. Carbon released to the active carbon reservoir via volcanism. Active Carbon Reservoir Inflow = Outflow Cliffs of Dover Credit: ©between ca. 1890 and ca. 1900 Detroit Publishing Company. Library of Congress, Prints and Photographs Division [reproduction number LC-DIG-ppmsc-08355] chalk = CaCO3! Photograph courtesy Robert Krimmel, USGS The eruption of Mount St. Helens 30 years ago on May 18, 1980 (pictured),  is the most devastating and most studied volcanic explosion in U.S. history. The blast killed 57 people and spewed 520 million tons of volcanic ash, darkening the skies of Spokane, Washington, more than 250 miles (400 kilometers) away. Over the past million years the earth has been in a quasi steady state where atmospheric CO2 concentrations have been constrained between 190 and 290ppm by the long term carbon cycle. This figure with the bucket represents this long term carbon balance where the amount of water (CO2) going into the bucket (atmosphere) equals the amount going out; steady state. Sources of carbon to the atmosphere were nearly equal to the sinks of carbon from the atmosphere over this time period.

the “active” and “inactive” carbon reservoirs So far we’ve talked about the long term carbon cycle. Cycling of carbon through geologic reservoirs occurs over million year timescales. These reservoirs are referred to as inactive carbon reservoirs because they interact with the atmosphere over geologic time scales rather than short time scales. There are many processes involving carbon that take place on much faster time scales; from seconds to hundreds of years. This includes carbon cycling through land plants and surface soils (the terrestrial biosphere) and through the surface ocean. These faster time scale processes earn these reservoirs the name of active carbon reservoirs. Active carbon reservoir: any reservoir/pool of carbon that interacts with the atmosphere on timescales less than hundreds of years. land plants and soils ocean atmosphere

active carbon cycle (preindustrial) Pg = Gt = billion tons or 1015 grams slide from Christopher Sabine

the human influence Inflow ≠ Outflow Carbon returned to the inactive carbon reservoir via carbon burial and plate tectonics. Carbon released to the active carbon reservoir via volcanism. Active Carbon Reservoir With industrialization, humans began adding significant quantities of CO2 to the atmosphere at staggering rates. For the bucket analogy, this means adding another water source to the bucket; causing water to spill out as the amount of water going into the bucket exceeds the amount exiting the bucket. As we extract and burn fossil carbon we are moving carbon from an inactive reservoir where it may have been stored for millions more years and we are adding it to the active carbon reservoir. As a result, we are adding another source of carbon to the atmosphere but we are Not introducing a sink of CO2 from the atmosphere that operates on the same time scale. This causes the concentration of CO2 to increase in the atmosphere. The increase in CO2 concentration of the atmosphere is approximately half that of what would be expected from the total human carbon emissions, suggesting that half of our CO2 emissions to the atmosphere are being reallocated to other storage reservoirs. These reservoirs are the land and oceans.

carbon units Alex Zolotar Current global fossil fuel emissions are equivalent to ~9-10 Pg C per year. Petagram Carbon (Pg C) = Gigaton Carbon (Gt C) = 1 billion tons of carbon a train filled with 1 Gt coal would wrap around the earth 4 times a train filled with 9 Gt coal would wrap around the earth 36 times! Steve Mellon/Post-Gazette 1Gt coal = 66,666 trains 66,666 trains = 100,000 miles circumference of earth at equator = 24,901 miles 6 May 2012: http://earthobservatory.nasa.gov/Features/CarbonCycle/ Diagram adapted from U.S. DOE, Biological and Environmental Research Information System. This diagram of the fast carbon cycle shows the movement of carbon between land, atmosphere, and oceans. Yellow numbers are natural fluxes, and red are human contributions in gigatons of carbon per year. White numbers indicate stored carbon. (Diagram adapted from U.S. DOE, Biological and Environmental Research Information System.) Why do we care where the carbon goes? Well, there is a large amount of uncertainty in how these various feedbacks may play out. In some cases, it isn’t just the magnitude of the feedback, but the sign of the feedback that is uncertain! Carbon Cycle Feedbacks! Permafrost Ocean circulation Ocean solubility pump Ocean biological pump CaCO3 feedback Ballast feedback Land feedbacks – CO2 fertilization (uncertain nutrient supply), soil respiration increases, land coverage/albedo changes, permafrost.

the Keeling curve http://keelingcurve.ucsd.edu/

~first Homo sapien fossil the Keeling curve vs. glacial/interglacial CO2 Human CO2 emissions ~first Homo sapien fossil natural glacial-interglacial cycles http://keelingcurve.ucsd.edu/

CO2 Partitioning (PgC y-1) atmospheric CO2 growth Total CO2 emissions Atmosphere CO2 Partitioning (PgC y-1) 1960 2010 1970 1990 2000 1980 10 8 6 4 2 Time (y) Where is the missing carbon? Using 1870 as the reference year (as in IPCC AR5 2013), cumulative emissions up to 2013 are 390±20 GtC from fossil fuels and cement, and 160±55 GtC from land use change, for a total of 550±60 GtC. Updated from Le Quéré et al. 2009

partitioning of carbon (2002-2011 avg.)

active carbon cycle (preindustrial + avg. fluxes 2000-2009) Pg = Gt = billion tons or 1015 grams Cumulative Carbon Emissions The cumulative carbon emissions are the sum of the total CO2 emitted during a given period of time. Total cumulative emissions since the beginning of the Industrial Revolution, 1750 to 2012, were 385±20 GtC from fossil fuels and cement, and 205±70 from land use change. Using 1870 as the reference year (as in IPCC AR5 2013), cumulative emissions up to 2013 are 390±20 GtC from fossil fuels and cement, and 160±55 GtC from land use change, for a total of 550±60 GtC. slide from Christopher Sabine

cumulative contributions to Global Carbon Budget Slide from the Global Carbon Project

ΔpCO2 = pCO2 (sea) – pCO2 (air) sea-air CO2 fluxes ΔpCO2 = pCO2 (sea) – pCO2 (air) CO2 out The largest uncertainty in the budget rests on the Land Use Change Emissions, which go into the Land Sink estimate. While the ocean is a carbon sink, it is not heterogeneous! CO2 in