What are Marine Heatwaves (MHWs)?

• An MHW is an extreme weather event where the ocean surface temperature rises significantly above average for an extended period.
• MHWs can last for weeks, months, or even years, impacting marine ecosystems globally.

The Link Between Climate Change and MHWs

• Rising Global Temperatures: The primary driver of intensified MHWs is the climate crisis. As global temperatures increase, the ocean absorbs a significant portion of this excess heat, leading to rising sea surface temperatures (SSTs).
• Increased Frequency, Duration, and Severity: The increase in SSTs directly contributes to more frequent, longer-lasting, and more severe MHWs. Studies show a clear correlation between rising global temperatures and the intensification of MHWs.

Impact of MHWs on Marine Life

• Devastating Consequences: MHWs can have catastrophic effects on marine ecosystems. They can cause:
  • Large-scale fish kills
  • Destruction of kelp forests
  • Coral bleaching, leading to reduced coral reproductivity and increased vulnerability to diseases
  • Disruption of the food chain and overall ecosystem health

Case Study: Western Australia

• Recent MHWs: Western Australia experienced severe MHWs in late 2024 and early 2025, linked to the death of over 30,000 fish.
• Climate Change Connection: Analysis shows that climate change made these MHWs up to 100 times more likely to occur.
• Worsening Conditions: The intensity of MHWs in the region is increasing, with SSTs reaching alarming levels above average.

The Future of MHWs

• Projected Increase: Studies predict a significant increase in the number and severity of MHWs as global temperatures continue to rise.
• Global Impact: The intensification of MHWs is a global concern, with potential impacts on marine ecosystems worldwide.

Conclusion

The climate crisis is directly linked to the intensification of marine heatwaves.

These extreme weather events have devastating consequences for marine life and ecosystems. Addressing climate change is crucial to mitigating the impacts of MHWs and protecting the health of our oceans.