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44.5D: Past and Present Effects of Climate Change

  • Page ID
    14174
  • Results of climate change, past and present, have been documented and include species extinction, rising sea levels, and effects on organisms.

    Learning Objectives

    • Describe the effects of current and geological climate change

    Key Points

    • Global warming has been associated with at least one planet-wide extinction event during the geological past; scientists estimate that during the Permian period, approximately 70 percent of the terrestrial plant and animal species along with 84 percent of marine species became extinct.
    • Glacier recession and melting ice caps are direct effects of current global climate change, ultimately leading to higher global sea levels; as glaciers and polar ice caps melt, there is a significant contribution of liquid water that was previously frozen.
    • Changes in temperature and precipitation are causing plants to flower earlier, before their insect pollinators have emerged; mismatched timing of plants and pollinators could result in injurious ecosystem effects.
    • This mismatched timing of plants and pollinators could result in injurious ecosystem effects because, for continued survival, insect-pollinated plants must flower when their pollinators are present.

    Key Terms

    • phenology: the study of the effect of climate on periodic biological phenomena
    • Permian: of a geologic period within the Paleozoic era; comprises the Cisuralian, Guadalupian, and Lopingian epochs from about 280 to 248 million years ago

    Documented results of climate change: past and present

    Scientists have geological evidence of the consequences of long-ago climate change. Modern-day phenomena, such as retreating glaciers and melting polar ice, cause a continual rise in sea level. Changes in climate can negatively affect organisms.

    Geological climate change effects

    Global warming has been associated with at least one planet-wide extinction event during the geological past. The Permian extinction event occurred about 251 million years ago toward the end of the roughly 50-million-year-long geological time span known as the Permian period. This geologic time period was one of the three warmest periods in earth’s geologic history. Scientists estimate that approximately 70 percent of the terrestrial plant and animal species and 84 percent of marine species became extinct, vanishing forever near the end of the Permian period. Organisms that had adapted to wet and warm climatic conditions, such as annual rainfall of 300–400 cm (118–157 in) and 20 °C–30 °C (68 °F–86 °F) in the tropical wet forest, may not have been able to survive the Permian climate change.

    Present climate change effects

    A number of global events have occurred that may be attributed to recent climate change during our lifetimes. Glacier National Park in Montana, among others, is undergoing the retreat of many of its glaciers, a phenomenon known as glacier recession. In 1850, the area contained approximately 150 glaciers. By 2010, however, the park contained only about 24 glaciers greater than 25 acres in size. One of these glaciers is the Grinnell Glacier at Mount Gould. Between 1966 and 2005, the size of Grinnell Glacier shrank by 40 percent. Similarly, the mass of the ice sheets in Greenland and the Antarctic is decreasing: Greenland lost 150–250 km3 of ice per year between 2002 and 2006. In addition, the size and thickness of the Arctic sea ice is decreasing.

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    Glacial recession: The effect of global warming can be seen in the continuing retreat of Grinnel Glacier. The loss of a glacier results in the loss of summer meltwaters, sharply reducing seasonal water supplies and severely affecting local ecosystems.

    This loss of ice is leading to rises in the global sea level. On average, the sea is rising at a rate of 1.8 mm per year. However, between 1993 and 2010, the rate of sea-level increase ranged between 2.9 and 3.4 mm per year. A variety of factors affect the volume of water in the ocean, including the temperature of the water (the density of water is related to its temperature) and the amount of water found in rivers, lakes, glaciers, polar ice caps, and sea ice. As glaciers and polar ice caps melt, there is a significant contribution of liquid water that was previously frozen.

    In addition to some abiotic conditions changing in response to climate change, many organisms are also being affected by the changes in temperature. Temperature and precipitation play key roles in determining the geographic distribution and phenology of plants and animals. Phenology is the study of the effects of climatic conditions on the timing of periodic lifecycle events, such as flowering in plants or migration in birds. Researchers have shown that 385 plant species in Great Britain are flowering 4.5 days sooner than was recorded during the previous 40 years. In addition, insect-pollinated species were more likely to flower earlier than wind-pollinated species. The impact of changes in flowering date would be mitigated if the insect pollinators emerged earlier. This mismatched timing of plants and pollinators could result in injurious ecosystem effects because, for continued survival, insect-pollinated plants must flower when their pollinators are present.

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