Explaining Climate Change

To review what you learned about isotopes, determine the mass ratio between a regular H₂O molecule and a ¹H₂¹⁸O molecule. Click the box below to check your answer.

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A regular water molecule made up of the most abundant isotopes of oxygen (¹⁶O) and hydrogen (¹H), resulting in a molecular mass of approximately 18 g/mol. A ¹H₂¹⁸O molecule has a molecular mass of 20 g/mol because its oxygen is a heavier isotope, with an atomic mass of 18. Putting this into a ¹H₂¹⁶O : ¹H₂¹⁸O ratio, we get 18 g/mol / 20 g/mol. This equals 0.9.

Open the Ice Core Extraction and Analysis learning tool and answer the following questions:

How are the layers of ice within the cores dated?
What characteristics of ice core layers signify when events, such as volcanic eruptions, have occurred?
What type of laboratory technique is used to characterize isotopes in ice? How does this technique work?

Question for Thought

Question: What are some possible reasons for historical fluctuations in atmospheric gas concentrations?

Hint: Think about the sources and sinks of atmospheric gases. For example, animals exhale carbon dioxide, volcanoes release sulfur and nitrogen compounds, soil organisms produce nitrous oxide, and dead plant material releases methane. Living plants, on the other hand, fix carbon dioxide through photosynthesis. How might changes in plant or animal populations affect atmospheric gas concentrations?