The year 2010 ended the warmest decade in Earth's history. The average global temperature was 58.3 degrees Fahrenheit (14.63 degrees Celsius), which ties the temperature in 2005 as the highest on record. In addition, 19 countries reported record heat in 2010 [source: EarthPolicy.org]. Some of the reasons for the temperature rise include:
- Greenhouse gas: Greenhouse gas emissions, such as carbon dioxide (CO2), nitrous oxide and methane from automobile exhausts and industries, trap heat in the atmosphere.
- Deforestation: Extensive logging is removing trees and plants that would otherwise absorb CO2.
- Oceans' absorption of CO2: Oceans help maintain a delicate equilibrium by absorbing CO2 from the atmosphere and reflecting heat from the sun. But this balance is difficult to match with global CO2 emission levels.
- Loss of sea ice: Glaciers help maintain the temperature of oceans, but with ice melting, there is less heat that is reflected back and more water to absorb it.
All of these reasons contribute, but many scientists agree that expansion of the greenhouse gas effect from human activities is warming the Earth the most [source: NASA]. Normally, sunlight passes through Earth's atmosphere and warms the planet's surface before reflecting back into space. With the greenhouse gas effect, most of the heat that normally would reflect and radiate back into space gets absorbed by the tiny molecules in greenhouse gases and warms the Earth's surface and lower atmosphere.
Over the past century, scientists have been tracking a significant uptrend in global temperature with a disturbing connotation attached to it: As the Earth gets warmer, the chances of a major heat wave occurring also begin to increase. Most importantly, scientists predict that over the next 40 years, the chances of a heat wave occurring during the summer will be 100 times greater than they are now [source: Global Development and Environment Institute, Tufts University]. And though 19 countries reported record highs in 2010, no country recorded record low temperatures. The Arctic has warmed at an even faster rate than the rest of the Earth, which has speeded up melting of the polar ice cap. Minor changes in temperature might not seem like much, but it only takes small changes in global temperature to make sea levels rise and affect weather patterns around Earth.
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