365 Days of Climate Awareness 1: SSPs

365 Days of Climate Awareness

Part 1: SSPs

Since nearly the beginning of its 33-year existence, the IPCC (Intergovernmental Panel on Climate Change) has modeled future climate possibilities based on a range of scenarios, extending from the most progressive, change-oriented to the most conservative. This is because natural scientists, in attempting to model an extremely complicated climate system, can't hope to predict human choices. (Only Hari Seldon can do that. h/t to Isaac Asimov)

The early IPCC modelers decided, with a team of sociologists, to create a range of likely historical trends. Each trend would be described, developed, and ultimately translated into a series of numerical inputs for the climate models (there are more than one, and their results are averaged). These inputs include economic activity, energy use, population growth or decline, and many others, on a regional basis around the world.

The core of these historical scenarios are the Shared Socioeconomic Pathways, or SSPs. There are five, and they themselves have evolved over the roughly thirty years since their creation. The most recent version, created in advance of the Sixth Assessment Report, is briefly summarized below:

    SSP1 (Sustainability): The world shifts gradually, but pervasively, toward a more sustainable path...
    SSP2 (Middle of the Road): The world follows a path in which social, economic, and technological trends do not shift markedly from historical patterns...
    SSP3 (Regional Rivalry): A resurgent nationalism, concerns about competitiveness and security, and regional conflicts push countries to increasingly focus on domestic or, at most, regional issues...
    SSP4 (Inequality): 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...
    SSP5 (Fossil-fueled Development): 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...

These are the IPCC's theorized likeliest courses for overall world social and economic events over the coming decades. Each scenario is the foundation for numerical inputs into the climate models. Each SSP leads to another set of acronyms: an RCP, or Representative [Carbon] Concentration Pathway. The RCPs are time series of mankind's carbon dioxide inputs into the world system, to year 2100 or beyond, each based on an individual SSP. The are also the subject of tomorrow's post.

Be well!

(llustration: IPCC. The result of five sets of climate runs through 2100, using the five different SSPs, showing average global air temperature and Arctic sea ice extent. Tomorrow's post will show the intermediate step, RCPs, in generating these results. Those numbers to the right of SSP1/2 etc. refer to the concentration pathways.)