Summary
A modelling study examined how solar radiation modification (SRM) could affect glacier melt across more than 3,800 Andean glaciers. Under high‑emissions climate change, glaciers show strong, continued shrinkage, but SRM slows this loss and reduces year‑to‑year variability. SRM performs similarly to a mid‑range climate scenario and appears more effective outside the tropics, where uncertainties remain. Although SRM cannot prevent overall glacier decline, it may moderate future losses and improve stability.
Abstract
– A modelling study investigated the influence of solar radiation modification (SRM) on glacier melting in the Andes compared to ‘worst-case’ and ‘middle-of-the-road’ climate change scenarios.
– Compared to the worst-case climate change scenario, SRM could reduce glacier shrinkage and variability in glacier change.
– Glacier shrinkage is predicted to be similar for SRM and the middle-of-the-road climate change scenario.
– The model showed SRM could be more effective outside the tropics, although there was a lot of uncertainty in tropical regions.
A Degrees-funded team, led by Professor Alfonso Fernández from the Universidad de Concepción, Chile, has investigated how solar radiation modification (SRM) might affect how quickly Andean glaciers are melting. The study included more than 3,800 glaciers across the Andes, extending from tropical right through to mid-latitude regions.
Glaciers are crucial for ecosystems along South America’s west coast, and their shrinking could lead to serious water shortages and increase the risk of natural disasters.
The team used the latest climate models to compare three scenarios: a middle-of-the-road climate change scenario leading to around 3°C warming by 2100, a high-emissions, worst-case climate change scenario leading to up to 5°C warming, and an SRM scenario that simulated dimming the sun to reduce warming in line with the middle-of-the-road scenario.
Avoiding instability
Under each scenario, the team calculated the glacier-wide ‘surface mass balance’: the difference between ice and snow accumulation and ice and snow melting A positive mass balance means a glacier will grow; a negative mass balance will cause it to shrink and retreat.
Under both climate change scenarios, the results indicated widespread negative mass balance throughout the 21st century, indicating that glaciers will continue to shrink across the Andes.
The SRM scenario showed a slower rate of glacier shrinkage when compared to the high-emissions climate change scenario, but was not significantly different from the middle-of-the-road climate change scenario. These findings align with similar studies that have examined other SRM scenarios applied to Iceland and high-mountain Asia.
The study also analysed the yearly variability in surface mass balance, finding that glacier conditions under SRM may be more stable compared to changing temperatures under high-emissions warming. This suggests that SRM interventions may make the Andean cryosphere – all the frozen components, including glaciers, snow and permafrost – more resilient to changing temperatures. While some glacier melting will inevitably occur, the Andes could avoid some of the instability caused by climate change, if the necessary mitigation actions are taken simultaneously.
Some loss locked in
The team stressed that regional differences must be considered, and their results showed that the effects of SRM on Andean glaciers could vary significantly depending on their location. In tropical regions, the differences between SRM and the high-emission scenario are often indistinguishable due to high uncertainty in the models. In non-tropical regions, SRM may lead to greater stability and less melting compared to the high-emission scenario, suggesting that SRM may be more effective in non-tropical areas.
The study finds that while SRM could theoretically cool the planet and slow down the shrinking of Andean glaciers in the 21st century, it cannot stop this process entirely due to expected and already emitted greenhouse gases. Interestingly, the team suggest that SRM might have worked to maintain Andean glaciers if it was started 50 years ago, but they recognise this is unrealistic because climate discussions and SRM models only became prominent around 35 years ago.
Alfonso said: “While SRM may offer a way to reduce the rate of glacier loss compared to high-emissions climate change scenarios, it is crucial to do more research and consider the broader impacts and uncertainties associated with this technology.”
Co-author and PhD researcher Francisco Manquehual-Cheuque added: “Our results also show that even with SRM, a certain amount of glacier loss is already locked in – it cannot nullify the emissions already released. Above anything else, these findings emphasise what we already know: we urgently need to reduce CO2 emissions.”