New approach to predicting glacier response to climate change shows significant impacts of every temperature increase

In a study that represents “a substantial step forward in predictive modeling” of glacier response to climate change, researchers present predictions for the fate of all Earth’s mountain glaciers, which total more than 215,000 under various policy-relevant climate scenarios. They report that even under the most optimistic scenarios, glaciers globally will lose substantially more mass and contribute to more sea-level rise than current estimates, including those published in the most recent IPCC report, indicate. “[E]very increase in temperature has significant consequences with respect to glacier contribution to sea level rise, the loss of glaciers around the world, and changes to hydrology, ecology, and natural hazards,” these authors, led by David Rounce, say. In a related Perspective, Guðfinna Aðalgeirsdóttir and Timothy James reflect on how recent studies have revealed that positive opportunistic framing of climate change is more effective at inciting public support for climate policies than focusing on urgency and consequences. They say the authors of this study, “while issuing a stark warning about the consequences of insufficient action, achieve this framing with an important message: Although it is too late to avoid losing many glaciers, any effort to limit global mean temperature rise will have a direct effect on reducing how many glaciers will be lost.”

Rates of glacier melt have increased over the past few decades, and the continued decline of these vulnerable features will affect sea level rise, freshwater availability for nearly 2 billion people, and risk from glacier-related hazards. Projecting glacier mass loss is critical to future global climate adaptation and mitigation efforts. However, a comprehensive understanding of how Earth’s more than 215,000 individual glaciers (excluding the Greenland and Antarctic ice sheets) will respond under various climate warming scenarios remains challenging. Existing projections are limited to regional scales and neglect key physical processes controlling glacier mass loss. To address these limitations, Rounce and colleagues took advantage of new datasets to produce a set of global glacier projections that explicitly account for glacier dynamics. They produced projections for all of Earth’s individual glaciers under +1.5°Celsius (C), +2°C, +3°C, and +4°C temperature change scenarios by 2100 relative to pre-industrial levels. The findings suggest that glaciers are projected to lose 26±6% to 41±11% of their total mass by 2100, relative to 2015, under temperature increases of 1.5°C to 4°C, respectively. This means that even under the best-case scenarios, where global mean temperature rise is limited to 1.5°C, as many as half of the planet’s glaciers will be lost by 2100. Based on recent climate pledges from COP-26, which project global mean temperature to increase by 2.7°C over the next century, Earth will likely experience a near-complete deglaciation of entire mid-latitude regions, including Central Europe, Western Canada and United States, and New Zealand; this will result in a much greater glacial contribution to sea-level rise than currently estimated.