The world is getting warmer. Whether the cause is the human activity or natural variability the preponderance of evidence says its human. Thermometer readings all around the world have risen steadily since the beginning of the industrial revolution.
According to an ongoing temperature analysis conducted by scientists at NASA’s Goddard Institute for Space Studies (GISS), the average global temperature on Earth has increased by about 0.8° Celsius (1.4° Fahrenheit) since 1880. Two-thirds of the warming has occurred since 1975, at a rate of roughly 0.15-0.20°C per decade.
But why should we care about one degree of warming? After all, the temperature fluctuates by many degrees every day where we live. The global temperature record represents an average over the entire surface of the planet. The temperatures we experience locally and in short, periods can fluctuate significantly due to predictable cyclical events (night and day, summer and winter) and hard-to-predict wind and precipitation patterns. But the global temperature mainly depends on how much energy the planet receives from the Sun and how much it radiates back into space—quantities that change very little. The amount of energy radiated by the Earth depends significantly on the chemical composition of the atmosphere, particularly the amount of heat-trapping greenhouse gases.
OVERVIEW
Why is just one- degree so devastating?
A one-degree global change is significant because it takes a vast amount of heat to warm all the oceans, atmosphere, and land by that much. In the past, a one- to two-degree drop was all it took to plunge the Earth into the Little Ice Age. A five-degree drop was enough to bury a large part of North America under a towering mass of ice 20,000 years ago. Global temperature records start around 1880 because observations did not sufficiently cover enough of the planet to that time. Generally, warming is greater over land than over the oceans because water is slower to absorb and release heat (thermal inertia). Warming may also differ substantially within specific land masses and ocean basins. Since the year 2000, land temperature changes are 50% greater in the United States than ocean temperature changes; two to three times greater in Eurasia; and three to four times greater in the Arctic and the Antarctic Peninsula. Warming of the ocean surface has been largest over the Arctic ocean, second largest over the Indian and Western Pacific Oceans, and third largest over most of the Atlantic Ocean.
Learn more by reading the FULL SCIENTIFIC BACKGROUND
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Select one of the following Class activities:
- Transforming Water
- Heatwave Safety