Arctic Sea Ice – September, 2012, had the lowest sea ice extent on record, 49 percent below the 1979-2000 average for that month.
Glaciers - On average, glaciers worldwide have been losing mass since at least the 1970s which in turn has contributed to observed changes in sea level. Measurements from a smaller number of glaciers suggest that they have been shrinking since the 1940s. The rate at which glaciers are losing mass appears to have accelerated over roughly the last decade.
Lake Ice - The time that lakes stay frozen has generally decreased since the mid-1800s. For most of the lakes in this indicator, the duration of ice cover has decreased at an average rate of one to two days per decade.
Snowfall - Total snowfall has decreased in most parts of the country since widespread observations became available in 1930, with 57 percent of stations showing a decline.
Snow Cover - Looking at averages by decade suggests that the extent of North America covered by snow has decreased somewhat over time. The average extent for the most recent decade (2003–2012) was 3.18 million square miles, which is 4 percent (132,000 square miles) smaller than the average extent during the first 10 years of measurement (1972–1981).
Snowpack - From 1950 to 2000, April snowpack declined at most of the measurement sites with some relative losses exceeding 75 percent.
As you discuss this article with students, it is important to reference the data that is being accumulated to support the reality of climate change. You will notice that each data set above and the data in the original EPA source may not provide conclusive evidence for climate change, but the accumulation of data paints a fairly conclusive picture of climate change.