Glaciers, sea ice, and continental ice sheets are being affected by climate change worldwide. NASA calls them "Sentinels of Change". In this section, you will examine plots of temperature trends in the polar regions available as time series from the NASA Goddard Institute for Space Studies (GISS). Data provides the backbone support of a STEM lesson and as you complete the following activities, you should think about how you may implement these data activities with your students.
Data Activity: Global Ice Viewer
Begin this data exploration by looking at the "Global Ice Viewer" to see why scientists are so concerned about the melting of the Earth's ice. Explore the interactive to see how climate change has affected glaciers, sea ice, and continental ice sheets. You can view comparison images of glaciers in specific areas, videos of glaciers changing over specific time periods and seasonal sea ice changes trending over time. What stories do these tell us about global climate change?
The data for this exercise comes from the GISS "Combined Land-Surface Air and Sea-Surface Temperature Anomalies (Land-Ocean Temperature Index, LOTI)" data set for Zonal annual means. These data are arranged so that users can plot time series of annual means for various latitudinal zones of the Earth from 1880 to the present. Note that the data are presented as a temperature index in degrees Celsius relative to the period 1951-1980 rather than absolute temperatures.
Mean Annual Temperature Anomalies
Review the "Zonal and Global Mean Annual Temperature" graph which presents change in temperature from 1880-2010. You can compare change in the Northern Hemisphere (red line), Southern Hemisphere (yellow line), and the Global (blue line) mean annual temperatures. Both annual data and smoothed data are presented. The plot of annual data presents every year in the record and shows considerable variability from year to year while the smoothed data averages the data for a defined length of time to reduce the variability while emphasizing the overall trend.
Which hemisphere exhibits the greatest warming trend? Can you suggest reasons for this?Answer
The Northern Hemisphere has a steeper temperature increase over the period of time covered by the data. A likely explanation is that temperatures in the Southern Hemisphere are moderated more by the oceans which cover a far greater portion of the Southern Hemisphere compared to the Northern Hemisphere.
Which hemisphere exhibits greater multi-annual variability? Why might this be the case?Answer
The Northern Hemisphere exhibits greater variability from year to year and seasonally due to the moderating effects of the oceans in the Southern Hemisphere.
Determine from the line equations the annual rate of temperature increases for global, northern and southern hemispheres over the period of record.Answer
The rate of increase in temperature is as follows:
- Global – 0.57°C/year
- Northern Hemisphere – 0.63°C/year
- Southern Hemisphere – 0.52°C/year
The "Antarctic and Global MAT Anomaly" graph shows Global and Antarctic temperature anomalies, in the zone 64° South latitude to 90° South latitude encompassing the Antarctic continent (blue line). Linear trend lines and the equations for these lines are also plotted.
Does this graph suggest a greater rate of temperature increase for the southern Polar region as compared to the global mean?Answer
Yes, the rate of temperature increase for the southern Polar region is much higher than the global rate of increase.
Describe the difference you see in the pattern of data points from 1900-1960 and 1960-2010? Can you think of a possible reason to explain this difference?Answer
The data points for the period 1900-1960 are much more variable than those for the latter portion of the record. Prior to 1960 the earlier measurements were from land-based temperature stations widely scattered whereas the more recent record uses satellite data and averages a larger area smoothing out the variability.
For the period of the Antarctic record, examine the linear trend line for the Antarctic data (red line) and determine the annual rate of increase in temperature.Answer
Finally, explore the "Global and Arctic MAT Anomaly" graph that shows Global and Arctic global mean annual temperature anomalies for 64° North latitude to 90° North latitude. Linear trend lines and the equations for these lines are also plotted.
Does this graph suggest a significantly greater rate of increase for the Arctic as compared to the global mean LOTI (blue line)?Answer
Yes, the rate of temperature increase for the Arctic is much higher than the global rate of increase.
What is the rate of temperature increase as determined from the linear trend line equation across the time series for the Arctic?Answer
After viewing the three graphs give one or two explanations that describe your findings.Answer
The graphs show evidence that the poles are warming more rapidly than the Earth as a whole. In particular, the Arctic appears to be more sensitive to changes in climate because of strong ice-albedo feedback, and the loss of ice, which plays a role in regulating the Arctic climate. It is because of this sensitivity that climate models predict that the Arctic will warm more rapidly than any other part of the globe.
How can the use of these data sets help your students understand the compelling evidence that the poles are warming faster than the Earth as a whole, and reasons behind this warming?
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Global Climate Change Modules
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