Human presence across the face of the Earth is
substantial and growing. Increasingly, from the perspective of outer space we can
see the "fingerprints" of human presence on our landscapes. From the herringbone
patterns of tropical deforestation, to the large square patches of agricultural
fields, to the concrete splotches of urban sprawl, humans have attained the
magnitude of a geological force as we reshape our environments. Scientists
estimate that between one-third and one-half of our planet's land surface has
been transformed by human enterprises. Yet, scientists cannot say what, if any,
long-term impacts these changes will have on global climate systems.
![CO2 graph](Images/co2.jpg) Figure 1: The graph above shows average carbon dioxide (CO2) concentration in
parts per million by volume (ppmv), observed continuously at the Mauna Loa
Observatory in Hawaii. Atmospheric CO2, a major greenhouse gas, has increased
approximately 40 ppmv since 1958, largely because of human activities.
Superimposed on the long-term increase is the annual cycle due to photosynthetic
activity (data archived at Carbon Dioxide Information Analysis Center, Oak Ridge
National Laboratory).
Since the industrial revolution, scientists have observed a continued and
accelerating rise in the levels of greenhouse gases in the atmosphere (Figure 1).
Of particular concern is the increase in the buildup of carbon dioxide,
which is a direct result of urban consumption of fossil fuels as well as
the widespread use of fires in the tropics for deforestation. Over the
last century, scientists have measured a 0.5-degree rise in average
global temperatures that is due, at least in part, to increased levels of
greenhouse gases. How will land plants respond to these changes in
temperature and carbon dioxide levels? Will they delay or accelerate the
global warming trend? Will plant biomes (e.g., forests, tundra, and
grasslands) move in response to climate change? Will the world's ice
sheets and glaciers retreat as warmer climates move to higher
latitudes? Scientists cannot answer these questions now. But with the
launches of NASA's Landsat-7 and Terra satellites, unprecedented new data
becomes available to scientists around the world that will help them
better understand and predict how Earth's changing land surfaces affected
climate, as well as how climate changes will further cause land surfaces
to change.
next: The Carbon Cycle
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- Changing Global Land Surface
- Introduction
- The Carbon Cycle
- Greenhouse Warming
- Plants, Snow & Ice
- Terra & Landsat Observations
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