National Academy of Sciences - Climate Change: Evidence and Causes
Northern Hemisphere annual average snow anomaly

Figure 1b. A large amount of observational evidence besides the temperature records shows that Earth’s climate is changing. For example, additional evidence of a warming trend can be found in the dramatic decrease in the extent of Arctic sea ice at its summer minimum (which occurs in September), decrease in spring snow cover in the Northern Hemisphere, increases in the global average upper ocean (upper 700 m or 2300 feet) heat content (shown relative to the 1955–2006 average), and in sea-level rise. Source: NOAA
Source: NAS
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