Ice and snow are reflective covers that turn away the Sun's warming rays but also function as protective thermal blankets under which much biological activity takes place. In the summer, ice and snow protect plants and animals by melting into water that nourishes them in times of drought. Climate change as a result of global warming has had an impact on Earth's snow and ice cover.

According to the Fifth Assessment Report (AR5) of the Intergovernmental Panel on Climate Change (IPCC) released in 2014, “It's virtually certain that the upper parts of the world's oceans have warmed since 1971… The oceans will continue to warm, and Arctic sea ice cover and Northern Hemisphere spring snow cover are very likely to continue to shrink during the 21st century… Ice sheets covering Greenland and Antarctica have been losing mass, Arctic sea ice and Northern Hemisphere spring snow cover have been shrinking, and glaciers have been retreating almost worldwide over the last twenty years.”

The Sixth Assessment Report will be released in stages between 2021 and 2022, but preliminary drafts and intermediate topic-specific publications are corroborating and expanding upon the existing picture. An IPCC Panel from 2016 mandated the creation of three additional reports during the Sixth Assessment cycle, including a report on climate change and land, a report on global warming of 1.5 degrees Celsius, and a special report on the ocean and cryosphere in a changing climate. According to this special report, there is high confidence that global warming has directly led to mass loss from ice sheets and glaciers, increasing temperatures in the permafrost, and reductions in snow cover and Arctic sea ice extent and thickness. The June Arctic snow cover extent on land has been calculated to be declining by more than 13 percent per decade from 1967 to 2018.

According to the world's leading meteorological associations, 2016 was the warmest year on record, followed by 2019. The five warmest years on record have occurred since 2015, and nine out of the ten warmest years ever have occurred since 2005. The Arctic is the area that has experienced the most rapid warming in recent decades. The IPCC AR5 notes robust evidence for the decline in Arctic sea ice since 1979. According to the US National Aeronautics and Space Administration (NASA), the Arctic is losing sea ice at the rate of 13 percent per decade, a comparable percentage to the calculated loss of snow cover extent described earlier.

The snow and ice cover involves much more than snowflakes that have accumulated on the ground. As snowflakes fall to Earth, they are tumbled in the wind, fractured and compacted, then often melted and refrozen. This initial deterioration results in the formation of ice crystals. These grains of ice may then coalesce with others, until all are nearly the same size. Throughout this process, air spaces within the snowpack are reduced in size as individual ice grains pack together and bond at their points of contact. Both the snowpack density and the mechanical strength of the snow increase substantially through this process. Water vapor then moves upward, reducing the size of the ice crystals at the bottom of the snowpack. The subsequent formation of depth hoar facilitates the movement of small animals as they forage under the snow during the winter. Under typical winter conditions, the snowpack is warmest at the bottom and coldest at the top.

As the temperature of the planet warms, the snowpack diminishes. The shrinking snowpack in the Arctic and Antarctic has received much attention as concern about global warming rises. However, climate change has already begun to leave a dramatic mark on more inhabited regions of the planet. In the 1990s, the inhabitants of Shishmaref, a Native American village on the Alaskan island of Sarichef, noticed that sea ice was forming later and melting earlier. The change meant that a protective skirt of ice no longer buffered the small settlement from destructive storm waves.

Numerous mountain systems, including the Canadian Rockies, have also experienced a reduction in snow and ice cover. The loss may disturb the sensitive ecosystem of the areas. The survival of many plants and animals depends on an annual snow cover.