Global Temperature Anomaly Map
Visit NASA NEO's Global Temperature Anomaly to observe values for months or years. These maps — developed by NASA’s Goddard Institute for Space Studies (GISS) — depict how much various regions of the world have warmed or cooled when compared with a base period of 1951-1980. They show temperature anomalies, or changes, not absolute temperature. (The global mean surface air temperature for that period was estimated to be 14°C or 57°F.)
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.
The period of 1951-1980 was chosen largely because the U.S. National Weather Service uses a three-decade period to define “normal” or average temperature. The NASA GISS analysis effort began around 1980, so the most recent 30 years at the time was 1951-1980. It is also a period when many of today’s adults grew up, so it is a common reference that many people can remember.
As the maps show, global warming doesn’t mean temperatures rise everywhere at the same time. Temperatures in a given month or year might rise 5 degrees in one region and drop 2 degrees in another. Exceptionally cold winters in one region might be followed by exceptionally warm summers. Or a cold month in one area might be balanced by an extremely warm month in another part of the globe. Generally, warming is greater over land than over the oceans because water is slower to absorb and release heat (thermal inertia). Warming may also vary substantially within specific land masses and ocean basins.
According to an ongoing temperature analysis conducted by 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. A 0.8 degree global change is significant because it takes a vast amount of heat to warm all of the oceans, atmosphere, and land on the planet by that much. In the past, a one- to two-degree global 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.
Exploring Annual Changes
Goal: Students will observe monthly images of changing temperatures, looking for any changes that are occurring throughout the year.
Distribute monthly global image.
Have students arrange images in chronological order.
Ask groups to identify annual cycles for their variable. Use the following guiding questions:
What do the colors represent?
Shades of red and orange indicate areas where the average annual temperatures are warmer than they were in that area during the base period from 1951-1980. Shades of blue show cooling compared to the base period. So if New England is red in a given year, then it is warmer than the average in New England from 1951-1980. If part of Canada is blue in a year, then it is cooler than the annual average during the base period. Black areas are where no data are available.
What changes do you see through the year? What explanations can you suggest for these patterns?
Choose a location or region. During which months do the extreme highs and lows occur? What explanations can you suggest for the timing of those extremes?
Which regions experience both the extreme highs and lows? Which regions don’t experience the extremes? Why do you think this happens?
What differences, if any, do you find between the year’s variations over the oceans versus the year’s variations over the continents?
Are there regions that remained relatively unchanged over the year? Why do you think this happens?
[Teaching Hint: if students have trouble locating significant changes have them focus their attention on one location on the image throughout the year.]
After several minutes, ask the groups to share with the entire class their discoveries of patterns and their interpretation of those patterns.