Measuring the Elements of Climate Change: Glacial Melting

By Mark Tausig

Discussions of climate change often focus on phenomena such as global warming and rising greenhouse gas emissions.  Ever wonder how we measure such things?  How do we know that the global temperature has increased? How do we measure greenhouse gas amounts? What about decarbonization, tree canopies, auto and truck emissions, sea-level rise, glacier melting, and environmental justice? 

In this series, we will learn how climate change indicators are measured and how they change over time. Reliable, ongoing measurement of these conditions is essential to monitor climate change and promote climate action.

Part 6: Glacial Melting

The recent environmental disaster in Nepal and Tibet, triggered by glacial deterioration, reflects a worldwide phenomenon driven by global warming: glacial melt and loss. Glacial melt is the rapid loss of ice from the world’s glaciers due to rising global temperatures, driven primarily by greenhouse gas emissions and ocean warming. When measuring glaciers for climate change impact, size does not matter; melt rate does.

Glaciers around the world can range from ice that is several hundred to several thousand years old and provide a scientific record of how climate has changed over time. By studying them, we gain valuable information about how rapidly the planet is warming. Today, about 10% of Earth’s land area is covered with glacial ice. Almost 90% is in Antarctica, while the remaining 10% is in the Greenland ice cap.

Since the early 1900s, many glaciers around the world have been rapidly melting. Human activities are at the root of this phenomenon. Specifically, since the industrial revolution, carbon dioxide and other greenhouse gas emissions have raised global temperatures, and as a result, glaciers are rapidly melting, calving off into the sea and retreating on land. Even if we significantly curb emissions in the coming decades, more that a third of the world’s remaining glaciers will melt before the year 2100.

When it comes to sea ice, 95% of the oldest and thickest ice in the Arctic is already gone. Scientists project that If emissions continue to rise unchecked, the Arctic could be ice free in the summer as soon as the year 2040 as ocean and air temperatures continue to rise rapidly.
 
–World Wildlife Fund; Why are glaciers and sea ice melting?

The main consequences of deglaciation are:

Sea level rise: Glacial melting has contributed to raising sea levels by 2.7 centimeters since 1961. Furthermore, the world’s glaciers contain enough ice — about 170,000 cubic kilometers — to raise sea levels by nearly half a meter.

Impact on the climate: Glacial thawing at the poles is slowing the oceanic currents, a phenomenon related to altering the global climate and a succession of increasingly extreme weather events throughout the globe. Disappearance of species: Glacial melting will also cause the extinction of numerous species, as glaciers are the natural habitat of a number of animals, both terrestrial and aquatic.

Less fresh water: The disappearance of glaciers also means less water for consumption by the population, a lower hydroelectric energy generation capacity, and less water available for irrigation. 

–NOAA; Climate change: mountain glaciers

The Table below shows Ice loss relative to 1970 for the glaciers in the WGMS’s climate reference network. Glacier mass balance is the annual balance between how much snow accumulates on a glacier and how much ice is lost through melting, sublimation (evaporation), or iceberg calving. Through 2024, these glaciers have lost more than 27 meters of water equivalent, which is roughly the same as slicing a 98-foot slab off the top of each glacier in the network.

Scientists have described more than two hundred thousand glaciers as part of the GLIMS Glacier Database and the Randolph Glacier Inventory), but only a small fraction of these have been consistently monitored for long enough to measure climate-related changes in their size or mass. Scientists refer to this global collection of about 60 glaciers as “climate reference” glaciers. “Before” and ‘after” photos of glaciers provide vivid evidence of glacial retreat over time.

The World Glacier Monitoring Service (WGMS) collects standardized observations on changes in mass, volume, area and length of glaciers with time (see the Table), as well as statistical information on the distribution of perennial surface ice). An international research team combines glaciological field observations with geodetic satellite measurements to generate estimates of glacial gain or loss.

Glaciers gain mass directly through snowfall and indirectly through snow movement from wind and avalanches. They lose mass through melting and sublimation (when water evaporates directly from solid ice). Glaciers that terminate in a lake or the ocean also lose mass through iceberg calving.

To see if a glacier is growing or shrinking, glacier experts check the condition of snow and ice at several locations on the glacier at the end of the melt season. The scientists check snow levels against stakes they’ve inserted in the glacier, dig snow pits in the surface to examine the sequence of seasonal layers, and insert long poles into the glacier to probe characteristics of the snow and ice. 

Generally, the difference in thickness of snow from the previous measurement indicates the glacier’s mass balance—whether the glacier has grown or shrunk.

Other measurement techniques include repeat photography and satellite images to measure changes in area and the advance or retreat of the glacier’s downhill edge. Scientists can estimate changes in glacier thickness over time with repeat measurements. 

Glacial melting is a global issue because the consequences of melt and shrinkage are world-wide, e.g. sea level rise and ocean current changes.  But, as the world has seen in Tibet and Nepal, glacial deterioration can have local consequences as well. It is also having geopolitical consequences as world powers vie for control of newly opened sea lanes in the Arctic.  

The thing is, if global warming is somehow stopped tomorrow, it will not result in the restoration of glaciers and the water they store.  

Measuring glacial melt is, therefore, important for providing warnings to seaside communities and low laying commercial infrastructure.  Glacial melting will continue so that documenting its progress is helpful for resilience and planning in light of global warming.

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Mark Tausig, Ph.D., is a volunteer writer for the New York League of Conservation Voters. He is a retired Professor of Sociology, where he studied health disparities, social networks, work and mental health, international health, and population aging in low—and middle-income countries. His latest book, Population Aging in Societal Context: Evidence from Nepal, will be published by Routledge later this year (2025).