Improving our understanding of both the Greenland and Antarctic ice sheets will be essential for reducing current uncertainty around climate tipping points – the thresholds in Earth’s systems beyond which large and irreversible environmental change will cascade.

According to new research – published this week in the journal Nature Communications Earth & Environment – polar ice sheets are critical for providing guidance amid a rapidly changing future climate, as they have some of the lowest temperature thresholds as well as strongest links to other climate tipping points.

But despite awareness of just how crucial it is for climate scientists to understand polar ice sheets, vast gaps in our knowledge around their behaviour remain. Scientists at the British Antarctic Survey have, therefore, positioned that greater progress is needed in their modelling, observation, and theoretical understanding.

Polar ice sheets are masses of ice exceeding 50,000 square-kilometres that cover land at the poles, formed over long periods of time through layers of snow accumulating and transforming into glacial ice. 

Together, the Greenland and Antarctic ice sheets hold over 99% of Earth’s land ice.

Using a conceptual climate tipping model, scientists at the British Antarctic Survey investigated how key components in our climate system interact and would be impacted by global warming at two levels: 1.5°C and 4.0°C. They found that polar ice sheets were responsible for substantial amounts of uncertainty in climate tipping projections.

“Climate tipping points represent a critical risk for human society over the next century – and a growing body of evidence demonstrates how much we have left to understand about these highly impactful risks,” said Jonathan Rosser, lead author on the study and researcher at the British Antarctic Survey.

“This study helps to focus our research onto areas with the greatest contributions to our uncertainty about the future.”

Environmental thresholds in the natural world have potentially huge impacts on human society if they are breached. Some are already at risk of being crossed, including the polar ice sheets, the Amazon Rainforest, and ocean circulation systems which act to regulate our weather and climate. Yet, despite the importance of these systems, there remains large uncertainty about how much warming is required to tip them.

The research from the British Antarctic Survey indicates that the behaviour of the Greenland and West Antarctic ice sheets is one of the most important factors in understanding how these tipping points will act.

One hypothesis is that the polar ice sheets are potentially at risk of being tipped at current levels of global warming, which may lead to cascades of tipping throughout other systems such as the ocean circulation. Scientists argue therefore that reducing this uncertainty in the behaviour of polar ice sheets – through modelling, observations, and theoretical understanding – is critical.

Using an established and simplified model for climate tipping elements, scientists have assessed the impact of key components of the Earth’s climate system on climate tipping risks. These components included the Arctic Sea Ice, El Niño Southern Oscillation (a climate pattern that involves temperature changes in the central and eastern tropical Pacific Ocean), the Greenland and West Antarctic Ice Sheets, the Atlantic Meridional Overturning Circulation (the conveyor belt-like system of ocean currents in the Atlantic Ocean), and the Amazon rainforest. 

Scientists used the model to understand which of these components are the most important for reducing uncertainty in projecting future climate.

In a climate simulation at 1.5°C above pre-industrial temperatures, most of the change in climate was driven by changes in the polar ice sheet, while in the 4.0°C scenario, many tipping points were found to be crossed.

According the latest reports from the IPCC – its AR6 Synthesis Report 2023 – global warming is “more likely than not” to reach 1.5°C in the near future. Considering the high uncertainty in climate prediction methods, the research from the British Antarctic Survey only demonstrates how much decision-makers should be taking precautionary approaches to the risk of triggering tipping points when planning for the future.

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