The latest climate change projections delivered by the IPCC in its 6th assessment report present a sobering picture for Australia’s coastal and marine regions. The latest climate change projections delivered by the IPCC in its 6th assessment report present a sobering picture for Australia’s coastal and marine regions. Rising sea level is projected to contribute to coastal recession in many locations. These changes in combination with increased ocean and air temperatures and decreased rainfall will alter ecosystems with far reaching impacts for coastal areas
Figure: Changes in the potential median shoreline position along sandy coasts by the year 2100 relative to 2010 (meters). Image credit: IPCC 2021, Regional Fact Sheet Australasia
Coasts:
- Likely global mean sea-level rise up to 1.01m by 2100 and 1.88m by 2150 (high emissions scenario). Sea level rise above this range – approaching 2 m by 2100 and 5 m by 2150 (high emissions scenario) – cannot be ruled out due to deep uncertainty in ice sheet processes.
- Sea level is committed to rise for centuries to millennia due to continuing deep ocean warming and ice sheet melt and will remain elevated for thousands of years.
- In Australia, in recent decades relative sea level has risen at a rate higher than the global average and sandy shorelines have retreated in many locations.
Oceans:
- Past GHG emissions have committed the global ocean to future warming. Over the rest of the 21st century, likely ocean warming ranges from 2–4 to 4–8 times the 1971–2018 change.
- Based on multiple lines of evidence, upper ocean stratification, acidification, and deoxygenation will continue to increase in the 21st century. Changes are irreversible on centennial to millennial time scales.
- In Australia, an increase in marine heatwaves and ocean acidity has been observed and is projected to continue. For example, ocean warming in the region of the East Australia Current is four times faster than the global average.
In Western Australia, the State government is increasing its investment in managing the impacts of climate change in coastal areas, with a focus on coastal erosion hotspots. However, additional work beyond hotspot erosion management will be required to address the social, environmental, and economic impacts resulting from altered coastal and marine systems.
Figure Note: Climate model projections (CMIP5) under a very high greenhouse gas emissions scenario. Negative values indicate shoreline retreat. The map shows the median result, there is a range of possibilities. These projections are of the potential retreat, in the absence of additional sediment sinks/sources or any physical barriers to shoreline retreat (Source: IPCC 2021; Regional Fact Sheet Australasia)
References
IPCC, 2021: Summary for Policymakers. In: Climate Change 2021: The Physical Science Basis. Contribution of Working Group I to the Sixth Assessment Report of the Intergovernmental Panel on Climate Change [Masson-Delmotte, V., P. Zhai, A. Pirani, S. L. Connors, C. Péan, S. Berger, N. Caud, Y. Chen, L. Goldfarb, M. I. Gomis, M. Huang, K. Leitzell, E. Lonnoy, J.B.R. Matthews, T. K. Maycock, T. Waterfield, O. Yelekçi, R. Yu and B. Zhou (eds.)]. Cambridge University Press. In Press. https://www.ipcc.ch/report/ar6/wg1/#SPM
See also the Regional Fact Sheet Australasia: https://www.ipcc.ch/report/ar6/wg1/downloads/factsheets/IPCC_AR6_WGI_Regional_Fact_Sheet_Australasia.pdf
Header image credit: The University of Western Australia (UWA) and Peron Naturalist Partnership
Content summarized from the first part of the Sixth Assessment Report; the detailed evidence will come out over the next year.
The latest IPCC report is a 40-page “Summary for Policymakers” that says that within a decade, global warming could push temperatures to 1.5 degrees Celsius above pre-industrial levels, and calls on policymakers to take urgent action on climate change. The United Nations has referred to the situation as a “code red for humanity” and in Australia, it is projected that extreme rainfall events, droughts, and bushfires will worsen.