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General Ecology – Lab 9 Humans and the carbon cycle OVERVIEW This lab uses a robust, modern model of the carbon cycle to give you an intuitive sense for how carbon circulates through the atmosphere, biosphere, oceans, and surface of the earth. This model is similar to ones presented by the Intergovernmental Panel on Climate Change. It allows you to experiment with how human input to the cycle might change global outcomes to the year 2110 and beyond. One particularly relevant human impact is the increase in atmospheric CO2 levels. Between the years 1850 and 2016, atmospheric concentrations have risen from 290 parts per million (ppm) to over 401ppm – a level higher than any known on Earth in more than 30 million years – and they continue to rise. Using the simulator (link below), you will experiment with the human factors that contribute to this rise and explore how different inputs to the carbon cycle might affect the concentrations of the greenhouse gas CO 2. Simulator link: http://www.learner.org/courses/envsci/interactives/carbon/carbon.html Note: In the simulator, compartments of the carbon carbon cycle that have a relatively large and stable baseline amount of carbon (soil, ocean surface, and deep ocean), are broken down into that baseline amount and the changing amount (preceded by a plus or minus sign) from running the simulator. For these sinks, just record and work with the changing amount throughout the exercises. Also, don’t forget to RESET/RELOAD the simulator page between simulations! CARBON CYCLE Step 1: Predictions and initial data. Using your Data Table, record the total Giga-tons (GT) of carbon in each part of the carbon cycle model at the start, at 2060, and then at 2110 (advancing with multiple clicks of the “Run Decade” button). Using the data you collect from the model, answer the following questions while thinking about how the model mimics real-life conditions. Note: The default setting for the increase in fossil fuel use per year is 2%. This rate of increase is also a reasonable projection for the increase in global energy use, as the world's economies continue to develop and populations grow. 1. If only one half of the flora in the world existed in 2110 (perhaps due to deforestation), what do you predict the atmospheric carbon level would be? How would you change the simulation to reflect this? 2. Predict what might happen if we were to double our fossil fuel emissions. How do you think the shape of the atm CO2 curve would change? Draw your prediction. Choose 1 of the sinks (terrestrial plants, deep ocean, soil, etc) and predict how its carbon level might change under this scenario. Tell us why you think this. CARBON CYCLE Carbon Cycle: Step 1 Gaseous Carbon Year Emissions 2010 2060 2110 218 733 Atmosphere X 720 1031 1244 Ocean Water Ocean Surface 1000 +107 +333 Fossil Fuels Deep Ocean 38000 +250 +1091 Oil and Gas 500 66 0 1 of 5 Coal Biosphere Carbon Soil Atmospheric CO2/ppm Terrestrial Plants 3500 1800 700 3170 +238 758 700 +341 899 – 391 569 1244 Step 2. Run online model. In many scenarios, the atmospheric concentration of CO2 is projected to increase from ~400ppm to beyond 700 ppm by the end of the century. However, this increase in atmospheric carbon doesn't account for all of the carbon emissions released by the combustion of fossil fuels (the smokestacks in the model). To find out where all the carbon really goes, run the simulation one decade at a time. Record the carbon emissions, and the total carbon in the Atmosphere and each of the carbon “sinks.” Note that 1 ppm of atmospheric CO2 is equivalent to 2.1 GT of carbon. Answer the questions below. 1. What is the relationship between an increase in fossil fuel extraction (each decade run of the simulation) and change in the carbon in terrestrial plants? How might this relationship change flora populations? What impact could twenty years at this level of extraction have on flora? 2. What is the relationship between an increase in total emissions (a.k.a. combustion) and increased carbon in the ocean surface? How might this change marine life populations? Think about the types or organisms that use CO2, and the subsequent trophic cascades that might occur.