The scientific consensus indicates that the Earth is likely to surpass the critical 1.5℃ warming threshold due to climate change. Moreover, research suggests that global warming may temporarily exceed the 2℃ threshold if atmospheric carbon dioxide (CO₂) levels surpass anticipated limits.
This overshooting of emissions targets is a serious concern as it could lead to irreversible changes, such as rising sea levels, dysfunctional ecosystems, species extinction risks, and loss of glaciers and permafrost.
A recent study has delved into the implications of a climate overshoot for the world’s oceans. This research, which employed simulations with Earth system models as part of the Coupled Model Intercomparison Project (CMIP6), analyzed the consequences of increased ocean temperatures and decreased oxygen levels associated with a climate overshoot. As temperatures rise, oceans hold less dissolved oxygen, impacting marine ecosystems. A metabolic index was used to gauge the energy balance of individual organisms, and results indicated that marine species’ habitats could significantly shrink and their viability decrease over centuries.
For instance, species like tuna that thrive in well-oxygenated surface waters will be forced towards the surface for hundreds of years, affecting fishing grounds and productivity. This study emphasizes the need for resource management to safeguard species abundance and food security, highlighting the long-lasting impact of a climate overshoot on marine ecosystems.
This research underscores the importance of not only avoiding peak temperature targets but also minimizing the duration that temperatures remain above these targets. It is better to return from a temperature overshoot than to linger at higher levels, but avoiding an overshoot altogether is the most desirable outcome. This underlines the urgency of reducing emissions significantly, achieving net-zero emissions by mid-century, and striving to keep global warming “well below” 2℃ as outlined in the Paris Agreement.
To improve our understanding of climate overshoots and their reversibility, better Earth system models and sustained observations are necessary. Additionally, new experimental frameworks are needed to address the potential impacts of climate overshoots and mitigate their long-term consequences. The study reinforces the imperative for immediate and substantial action to address climate change and avoid irreversible damage to the planet’s ecosystems.