A recent study in the Proceedings of the National Academies of Science (open access article) assesses prospective sea-level rise over the course of the next 2000 years, combining paleo-reconstructions of sea-level rise and simulations from physical models focusing on the four main components that contribute to sea-level change.

Among the study’s findings:

1. Thermal expansion yields a global mean sea-level rise of 0.38m with a homogenous increase of ocean temperature by 1C;
2. The total contribution of all glaciers (all land ice excluding ice sheets) to sea-level rise over the next 2000 years is ~0.6m;
3. The potential contribution of the Greenland Ice Sheet is projected to be 0.18m °C^-1 up to a 1C temperature increase and 0.34m °C^-1  for temperature increases between 2-4C;
4. Simulated temperature rise over the next two millennium yields a 1.2m rise in sea level associated with melting of the Antarctic Ice Sheet;
5. On a 2000 year time scale, the contribution of the sources outlined above will be largely independent of the projected warming path during the first century;
6. The total sea-level commitment from all sources is 2.3m °C^-1 over 2000 years. However, the melting of the Greenland Ice Sheet ultimately results in 6m of sea-level rise over the course of several ten thousand years.

This study could stimulate some good classroom discussion. Some potential questions:

• In the context of questions of inter-generational equity, do these potential impacts substantially expand the scope of generations whose interests must be acknowledged and protected?;
• What are the implications of projected long-term rises in sea-levels for adaptation initiatives?
• What are the most significant sources of uncertainty associated with paleo-climatic sea level rise and temperature records?

To date, most research on the possible impacts of ocean acidification on marine organisms has focused on potential adverse impacts on secretion of calcium carbonate in species e.g. corals and echinoderms. However, a study published in the latest issue of the  journal Nature Climate Change demonstrates potential impacts on other biomaterials critical for bivalve molluscs, a group of species that provide for than $1.5 billion in revenue to the global aquaculture industry.

Mytilid mussels are competitive dominant species in many rocky shore ecosystems throughout the world. This is largely attributable to their ability to attach themselves to bare rocks with byssal threads, which are formed from collagen-like liquid precursors that polymerizes into a stiff and extensible thread. Byssal threads contain high concentrations o f a modified amino acid and histidine-metal crosslinkages that appear critical to facilitating surface adhesion and self-healing following deformation.

In the study, carbon dioxide was increased from 300 to 1,500 μatm (a pH decline from 8.0 to 7.5). Under high carbon dioxide concentrations (1,200 μatm), the study found substantial diminution of the performance of bysall performance, including a 35-10% decline in tenacity. The authors concluded that this could adversely affect community and ecosystem dynamics given the importance of mussels’ ability to securely attach themselves to rocks.

Of course, ocean acidification is not a manifestation of climate change, but rather a parallel impact of rising levels of carbon dioxide concentrations. The potential impacts of carbon dioxide emissions on an array of bio-structures may provide an additional rationale for focusing climate policymaking on reducing this discrete greenhouse source. It thus provides a good gateway for discussing the interface of efforts to reduce greenhouse gas emissions and to confront ocean acidification, as well as the appropriate regimes to address these issues, including coordination of initiatives.