ENVI 101 Test #2

Why do the atmospheric oxygen measurements disprove an oceanic or volcanic source for the increase in atmospheric CO2?

Because only CO2 emissions from fossil fuel combustion should be accompanied by a drop in atmospheric O2 as part of the combustion reaction. This drop would not accompany volcanic or oceanic emissions.

Describe two ways that human activities add carbon dioxide into the atmosphere.

Burning fossil fuels Cement production (carbon dioxide is releases directly during cement production, heat is needed which comes from the burning of fossil fuels, and vegetation is removed which absorbs carbon dioxide from the atmosphere.

Name two ways carbon dioxide naturally enters the atmosphere. Name two ways nature removes carbon dioxide from the atmosphere.

Carbon dioxide naturally enters the atmosphere when anaerobic bacteria that decompose other organic matter, when animals that exhale carbon dioxide during respiration, and during occasional volcanic activity. Carbon dioxide is naturally removed from the atmosphere by plants consuming it in the process of photosynthesis and water dissolving carbon dioxide.

Explain how isotopes help us identify human activities as the reason atmospheric carbon dioxide is increasing.

Carbon from the biosphere has low amounts of carbon-13, but (relatively) large amounts of carbon-14. Carbon from a volcano has large amount of carbon-13 and basically no carbon-14. Carbon from fossil fuels has low amounts of carbon-13, and basically no carbon-14. Analysis of the carbon added to the atmosphere shows that its isotopic composition matches fossil fuels.

Explain how "chemical weathering" removes CO2 from the atmosphere. What is the weathering chemical reaction? Can this process play an important role in counteracting the increase in atmospheric carbon dioxide caused by humans?

Chemical weathering occurs when atmospheric carbon dioxide dissolves into rainwater and this falls on rocks. The rain breaks down the rocks, both from the physical impact and from the weathering reaction: CaSiO3 + CO2 -> CaCO3 + SiO2 (equation 5.5) The carbon then runs into the ocean. In this way, the carbon is removed from the atmosphere. This process cannot play any role in the problem of modern climate change because it is slow — it takes millions of years to significantly affect atmospheric carbon dioxide.

Describe the processes that transfer carbon from the atmosphere to the land and from the land to the atmosphere. What are the chemical reactions that describe these processes?

Describe the processes that transfer carbon from the atmosphere to the land and from the land to the atmosphere. What are the chemical reactions that describe these processes?

What is it about methane that enables it to absorb several wavelengths of infrared light as strongly as it does?

Hydrogen does not produce carbon dioxide. In the presence of oxygen, the only product is water.

Are nitrogen and oxygen greenhouse gases? Why or why not?

No, they are not. Both gas molecules are so simple that they can't do much with any absorbed light.

What is it about methane that enables it to absorb several wavelengths of infrared light as strongly as it does?

What is it about methane that enables it to absorb several wavelengths of infrared light as strongly as it does?

Your aunt asks you how we know that volcanoes are not responsible for the observed increase in carbon dioxide. What do you tell her?

Your aunt asks you how we know that volcanoes are not responsible for the observed increase in carbon dioxide. What do you tell her?

Of the carbon dioxide humans add to the climate, approximately half is removed within a few decades. Where does it go? How would it affect the climate if, all of the sudden, all the carbon dioxide we emit stayed in the atmosphere?

Of the carbon dioxide removed from the atmosphere, about half goes into the ocean and half goes into the land-biosphere. If these sinks were to suddenly stop, then the rate of increase of atmospheric carbon dioxide would about double.