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Global Warming

Through Earth history, increase in greenhouse gases in the atmosphere correlate with high global temperatures.

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Global Warming

How can things change so quickly?

Glaciers and ice sheets are melting. This can be seen clearly in photographs. The glaciers advanced during the Pleistocene ice age. They have been melting back since then, except for during the Little Ice Age. However, the rate of melting has increased tremendously in recent decades.

Temperature Variations

Since the end of the Pleistocene, Earth’s temperature has risen. The image below shows how it changed over just the last 2000 years ( Figure below ). The Medieval Warm Period was a time of somewhat higher average temperatures. The Little Ice Age was a time of somewhat lower average temperatures. But for each time, the anomaly (the difference from average temperature) was less than 1° C (1.8° F). Still, the overall trend is slightly upward.

Earth’s temperature (0 C.E. – 2006). Different sets of data all show an increase in temperature since about 1880 (the Industrial Revolution).

Recent Temperature Trends

Since the mid 1800s, Earth has warmed up quickly ( Figure below ). The 14 hottest years on record have all occurred since 1900. As of the end of 2011, nine of the 10 hottest years ever have occurred since 2000! This temperature rise is what is usually meant by global warming .

Earth’s temperature (1850–2007). Earth has really heated up over the last 150 years. Do you know why?


  • global warming : Warming of Earth’s atmosphere since the late 19th century and the projected continued warming.


  • Average global temperature has been rising since the end of the ice ages.
  • The largest temperature rise has been in the past two decades.
  • The rise in Earth's temperature since the late 19th century is referred to as global warming.


Use the resource below to answer the questions that follow.

  1. How much has the global temperature risen in the last few decades?
  2. What contributes to global warming?
  3. What is the greenhouse effect?
  4. What is the evidence for global warming?
  5. What was the warmest recorded year?
  6. What gases have been recorded at their highest levels in history?
  7. What do researchers predict will happen?


  1. What have been the temperature trends in the past 2000 years?
  2. How is the rise in temperatures since the late 19th century different from the rise since the end of the Pleistocene?
  3. What is global warming?


global warming

global warming

Warming of Earth’s atmosphere since the late 19th century and the projected continued warming.

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