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7: The Carbon Cycle

  • Page ID
    50833
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    Introduction

    While water undoubtedly has significant impacts on Earth’s Climate, the number one culprit of our current Climate Change crisis is Carbon. Specifically, in two forms: Carbon Dioxide (CO2) and Methane (CH4). Both of these gases are greenhouse gases, which are gases that, while mostly transparent to incoming shortwave radiation, are highly absorbent to outgoing longwave radiation, resulting in additional heat being trapped in the Earth System. While there are numerous other greenhouse gases, Carbon Dioxide and Methane have by far the greatest impacts and are therefore of importance to climate scientists.

    A pile of black carbon powder.
    Figure \(\PageIndex{1}\): Black Carbon is one of many forms that Carbon takes on as it moves throughout the Earth System. (Public Domain; FK1950 via Wikimedia Commons)

    It's important to understand that while both Carbon Dioxide and Methane have anthropogenic sources, they are both important components of the Earth System and regularly cycle through its various components. In fact, it’s those natural cycles that have been altered by human activity that are the chief cause of excess Carbon in the atmosphere and subsequent warming. In this investigation, we will examine the Carbon Cycle and a few ways humans have altered it.

    Objectives
    • Identify key Carbon sources, reservoirs, and sinks in the Earth System
    • Differentiate the short-term Carbon Cycle from the long-term Carbon Cycle
    • Investigate how humans have disrupted the Carbon Cycle
    Navigational Note

    Investigation 6 has 22 questions in total, and the list is continuous, carrying over from the first to the last subpages of the investigation.

    • 7.1: Components of the Carbon Cycle
      This page highlights carbon's importance as the fourth most abundant element, essential for life and comprising 19% of human mass. It details the Carbon Cycle, including sources that add carbon to reservoirs and sinks that remove it, with significant reservoirs like soil, atmosphere, and oceans. The page also discusses the impact of human activities on carbon absorption, and the processes of photosynthesis and respiration that help regulate carbon levels in biomass and oceans.
    • 7.2: Ocean Acidification and Short Term Carbon Cycle
      Excess atmospheric CO2 eventually dissolves in water, forming carbonic acid and lowering ocean pH. This is called Ocean Acidification. It impacts the marine ecosystems, especially calcifying organisms such as coral, and presents data showing declining pH over time. Additionally, it affects the Short-Term Carbon Cycle, emphasizing seasonal CO2 fluctuations due to photosynthesis and respiration, while noting a general upward trend in CO2 concentrations.
    • 7.3: Long Term Carbon Cycle
      This page explores the Long-Term Carbon Cycle, including the Geologic and Biological Legs, and highlights human impacts, particularly through fossil fuel use, leading to climate change. It contrasts fossil fuel consumption globally, noting that while China leads in total usage, Americans consume significantly more per capita. The U.S. remains the largest fossil fuel consumer, indicating a critical need for reductions in both developed and developing nations.
    • 7.4: Accessible Descriptions
      This page provides accessible descriptions for the images in the Investigation.

    Thumbnail: Black Carbon by FK1955 by NASA is in the Public Domain.


    This page titled 7: The Carbon Cycle was last modified on Tue, 01 Sep 2026 01:34:22 GMT and is shared under a CC BY 4.0 license and was authored, remixed, and/or curated by Neel Desai and Alicia Mullens.

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