Ocean Acidification: Saturation State - Climate Model: SSP2 (Middle of the Road) - 2015 - 2100

Climate and Earth system models are used for a variety of purposes - from the study of dynamics of the weather and climate system of the past to projecting future climate. These models simulate the physics, chemistry and biology of the atmosphere, land and oceans, and require massive supercomputers to generate climate projections.

An international team of climate scientists, economists and earth systems modelers have built a range of new "pathways" that examine how global society, demographics and economics might change over the next century. They are collectively known as the "Shared Socioeconomic Pathways" (SSPs). World Climate Research Programme climate modeling working group, through international science coordination and partnerships, designed the framework for these climate models to inform the Intergovernmental Panel on Climate Change Sixth Assessment Report, AR6.

NOAA's Geophysical Fluid Dynamics Laboratory (GFDL) has created several fully coupled climate and earth system models that can utilize the SSPs to glimpse into the future. Global climate models represent the planet as millions of grid boxes and then solve mathematical equations to calculate how energy is transferred between those boxes using the laws of thermodynamics. If done correctly, these models of how energy is cycled through all parts of the planet can be used to estimate dozens of environmental variables (winds, temperature, moisture, ocean acidification, etc.). The models are tested by simulating historical conditions and then matching the results to our historical observational records. If the models can adequately recreate the past, they are then run forward in time to project what may happen in the future.

Ocean acidification is an often overlooked consequence of humankind's release of carbon dioxide emissions into the atmosphere from fossil fuel burning. Excess carbon dioxide enters the ocean and reacts with water to form carbonic acid, which decreases ocean pH (i.e., makes seawater less basic), and lowers carbonate ion concentrations. Organisms such as corals, clams, oysters, and some plankton use carbonate ions to create their shells and skeletons. Decreases in carbonate ion concentration will make it difficult for these creatures to form hard structures, particularly for juveniles. Ocean acidification may cause some organisms to die, reproduce less successfully, or leave an area. Other organisms such as seagrass and some plankton species may do better in oceans affected by ocean acidification because they use carbon dioxide to photosynthesize, but do not require carbonate ions to survive. Ocean ecosystem diversity and ecosystem services may therefore change dramatically from ocean acidification.

In this dataset, surface ocean aragonite saturation state is shown as projected by the SSP2 scenario, using GFDL’s ESM4 model between 2015 and 2100. SSP2-4.5 is an intermediate greenhouse gas emissions scenario where carbon dioxide emissions continue around current levels until 2050, then decrease but do not reach net zero by 2100. The resolution of the climate model is 1/4 degree for the oceans and 1 degree for the atmosphere.

Aragonite saturation state is commonly used to track ocean acidification because it is a measure of carbonate ion concentration. Aragonite is one of the more soluble forms of calcium carbonate and is widely used by marine calcifiers (organisms with calcium carbonate structures) to build their shells and calcium carbonate structures. Corals and other calcifiers are more likely to survive and reproduce when the saturation state is greater than three. When aragonite saturation state falls below 3, these organisms become stressed, and when saturation state is less than 1, shells and other aragonite structures begin to dissolve.

For more information on understanding SSPs we found this carbonbrief.org article very informative.

(Note: OnlySSP1, SSP2 and SSP5 are available on SOS)

The world shifts gradually, but pervasively, toward a more sustainable path, emphasizing more inclusive development that respects perceived environmental boundaries. Management of the global commons slowly improves, educational and health investments accelerate the demographic transition, and the emphasis on economic growth shifts toward a broader emphasis on human well-being. Driven by an increasing commitment to achieving development goals, inequality is reduced both across and within countries. Consumption is oriented toward low material growth and lower resource and energy intensity.

The world follows a path in which social, economic, and technological trends do not shift markedly from historical patterns. Development and income growth proceeds unevenly, with some countries making relatively good progress while others fall short of expectations. Global and national institutions work toward but make slow progress in achieving sustainable development goals. Environmental systems experience degradation, although there are some improvements and overall the intensity of resource and energy use declines. Global population growth is moderate and levels off in the second half of the century. Income inequality persists or improves only slowly and challenges to reducing vulnerability to societal and environmental changes remain.

A resurgent nationalism, concerns about competitiveness and security, and regional conflicts push countries to increasingly focus on domestic or, at most, regional issues. Policies shift over time to become increasingly oriented toward national and regional security issues. Countries focus on achieving energy and food security goals within their own regions at the expense of broader-based development. Investments in education and technological development decline. Economic development is slow, consumption is material-intensive, and inequalities persist or worsen over time. Population growth is low in industrialized and high in developing countries. A low international priority for addressing environmental concerns leads to strong environmental degradation in some regions.

Highly unequal investments in human capital, combined with increasing disparities in economic opportunity and political power, lead to increasing inequalities and stratification both across and within countries. Over time, a gap widens between an internationally-connected society that contributes to knowledge- and capital-intensive sectors of the global economy, and a fragmented collection of lower-income, poorly educated societies that work in a labor intensive, low-tech economy. Social cohesion degrades and conflict and unrest become increasingly common. Technology development is high in the high-tech economy and sectors. The globally connected energy sector diversifies, with investments in both carbon-intensive fuels like coal and unconventional oil, but also low-carbon energy sources. Environmental policies focus on local issues around middle and high income areas.

This world places increasing faith in competitive markets, innovation and participatory societies to produce rapid technological progress and development of human capital as the path to sustainable development. Global markets are increasingly integrated. There are also strong investments in health, education, and institutions to enhance human and social capital. At the same time, the push for economic and social development is coupled with the exploitation of abundant fossil fuel resources and the adoption of resource and energy intensive lifestyles around the world. All these factors lead to rapid growth of the global economy, while global population peaks and declines in the 21st century. Local environmental problems like air pollution are successfully managed. There is faith in the ability to effectively manage social and ecological systems, including by geo-engineering if necessary.

Narratives for each Shared Socioeconomic Pathway, from Riahi et al 2017.

• Climate Literacy and Energy Awareness Network (CLEAN): Teaching Climate and Energy - Principle 5
• Climate Interactives - Climate Change Solutions Simulators
• Climate Literacy and Energy Awareness Network (CLEAN): Webinar Series
• Climate Literacy and Energy Awareness Network (CLEAN): Climate Model Resource Collection
• Data Puzzles - CIRES Education and Outreach
• Antarctica: Connecting Climate Change, Melting Ice Shelves, and Pooping Penguins - CIRES Education and Outreach
Arctic Feedbacks - Not All Warming Is Equal - CIRES Education and Outreach
• Climate and Resiliency Education - CIRES Education and Outreach

For more technical information on the World Climate Research Programme go to the Earth System Grid Federation.

• Dunne, J. P., Horowitz, L. W., Adcroft, A. J., Ginoux, P., Held, I. M., John, J. G., ... & Zhao, M. (2020). The GFDL Earth System Model version 4.1 (GFDL‐ESM 4.1): Overall coupled model description and simulation characteristics. Journal of Advances in Modeling Earth Systems, 12(11), e2019MS002015.
• O’Neill, B. C., et al., The roads ahead: Narratives for shared socioeconomic pathways describing world futures in the 21st century, Global Environ. Change (2015), .
• O'Neill, B. C., et al., The Scenario Model IntercomparisonProject (ScenarioMIP) for CMIP6,Geosci. Model Dev., 9, 3461-3482, doi:10.5194/gmd-9-3461-2016, 2016.
• Riahi, K. et al., The Shared Socioeconomic Pathways and their energy, land use, and greenhouse gas emissions implications: An overview, Global Environmental Change, Volume 42, 2017, Pages 153-168,