In Lab 4, you explored the history of the cryosphere and looked at indicators of past climate, including ice cores. Now, you will consider the future of the cryosphere in a changing climate and how scientists use models to make predictions.
Climate Models
×
Climate Model Schematic. Note the grid cells around the globe. Climate models are built with mathematical equations that characterize the Earth systems in 3-D. Click image for larger view. Source: NOAA
Climate models are constructed using basic physical equations describing how the climate system works in three dimensions, as pictured in the graphic, right. This means equations must be included that describe the Earth system and its processes, such as the ocean, the atmosphere, the land, hydrologic and cryospheric processes, terrestrial and oceanic carbon cycles, and atmospheric chemistry. Unlike weather forecasting models, which are constantly updating with changing real-time data and describe the daily sequence of environmental conditions starting from a present state and working forward in time (to as far as a week with some reliability), climate models are based on the physics and chemistry of the Earth system to describe the average conditions in the future.
To complete a climate model, the physical equations, which represent how the spheres interact, are coupled with scenarios (described below) of how Earth's human population, land use, and economy could evolve. Once a climate model is run, the model output data is compared with the observed data from the past. This process allows scientists to check the accuracy of the models.
Watch this brief video from the Australian science agency CSIRO for an explanation of climate models:
Climate Modeling from CSIRO
Worldwide, various teams of scientists have modeled climate change and the subsequent impacts to the year 2100 and beyond. While the models show that rising global temperatures generally characterize the future world, human behavior will determine how dramatic the changes may be.
What is a scenario?
A scenario is an image of a potential future that is based on historical knowledge and expectations of future change. The IPCC scenarios are based on a data-driven pathway (or narrative) of what events have occurred in the past and how the future may unfold.
The scenarios describe the relationships between the forces driving greenhouse gas and aerosol emissions and their potential future change during the 21st century for the globe. The most recent models also include pathways representing different projections of a set of influential socioeconomic factors, including population growth, technological development, economic development, and their associated energy, land use, and emission implications.
Diagram of SRES Scenarios—common "roots" but branch in different directions depending on the storyline. Click image for larger view. Source: IPCC
Older IPCC reports used scenarios, known as SRES, that incorporated both emissions and socioeconomic elements into single scenarios. These SRES scenarios (which went by storyline names A1, A2, B1, B2, A1Fi) were too broad and difficult to fine tune with updated data. Later, the IPCC separated these two elements into separate pathways, known as RCPs and SSPs, which allowed scientists to clarify different emissions pathways and different socioeconomic pathways independently. However, SSPs scenarios were not completed in time for the 2013 IPCC report (AR5), so most pathway scenarios prior to 2020 will show only RCP pathways. Both RCPs and SSPs were first combined for complete modeling scenarios for the IPCC's AR6 report in 2021.
SSPs
×
Diagram of SSPs. Click image for larger view. Source: O'Neill, 2017
Shared Socioeconomic Pathways (SSPs) look at projected global socioeconomic changes until 2100. These scenarios consider possibilities for countries globally and how each may choose to approach their future socioeconomic development. There are five narratives that consider a range of possibilities.
SSP1 Sustainability – Taking the Green Road (Low challenges to mitigation and adaptation)
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.
SSP2 Middle of the Road (Medium challenges to mitigation and adaptation)
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.
SSP3 Regional Rivalry – A Rocky Road (High challenges to mitigation and adaptation)
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.
SSP4 Inequality – A Road Divided (Low challenges to mitigation, high challenges to adaptation)
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.
SSP5 Fossil-fueled Development – Taking the Highway (High challenges to mitigation, low challenges to adaptation)
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.
RCPs
Representative Concentration Pathways (RCPs) looks at possible future greenhouse gas emissions. The numbers in the RCPs stand for the amount of radiative forcing a difference to Earth's energy balance, which results in either warming or cooling (measured in watts per meter squared or W/m2) that the atmosphere will reach before leveling off. As the radiative forcing is caused primarily through the rise in greenhouse gases, the number will, therefore, also correspond to a concentration of GHGs in the atmosphere. In order to simplify calculations, all of the GHGs have been given a CO2 equivalency (CO2e) for modeling.
Since 2013, when four RCPs were modeled, the IPCC has expanded their RCPs total to seven (from high emissions to low): 8.5, 7.0, 6.0, 4.5, 3.4, 2.6, 1.9. Of these seven, five were chosen to focus on for the most recent IPCC report (AR6).
RCP8.5: energy-intense growth pathway with >8.5 W/m2 by 2100
RCP7.0: growth with high CO2 and non-CO2 emissions, including aerosols
RCP4.5: leveling off of emissions mid-century
RCP2.6: emissions peak and begin to fall starting early in 21st century, implied net zero emissions in the second half of the century.
RCP1.9: this RCP was created in order to model the 1.5C of warming by 2100 allowed by Paris Climate agreement; implied net zero emissions around the middle of the century.
SSPs + RCPs = SSP Scenarios
×
Scenarios used in AR6, with the radiative forcing categories and 5 socio-economic storylines upon which they are built. Click image for larger view. Source: IPCC WG1
By combining the SSPs and RCPs, a number of combined scenarios are possible. However, because the SSPs have assumed certain future socioeconomic trajectories, there are RCPs they cannot easily match with—for example, SSP1, which is focused on sustainability, will not match with RCP8.5's high emissions pathway; similarly, RCP1.9, which has very low emissions and would require consensus building, can't match with SSP3, which models a socioeconomic pathway of rivalry between countries that don't work together. These assumptions helped scientists to narrow their focus to models using five different combined scenarios.
According to the IPCC, the five combined scenarios (in white text in image at right) have been designed to span a wide range of possible future conditions, including a no-additional-climate-policy scenario of SSP3-7.0, and a strong mitigation scenario with SSP1-1.9. The scenarios don't try to forecast how events will happen in the future or account for the impact of climate change on the SSPs, nor do they try to prove which, if any, is more likely than another.
2. Find the box below left, labeled Regional Information. Click the lower right corner of this box to access the Advanced version of the climate models the temperature data is based on.
Provenance: IPCC AR6 WG1 Reuse: This item is offered under a Creative Commons Attribution-NonCommercial-ShareAlike license http://creativecommons.org/licenses/by-nc-sa/3.0/ You may reuse this item for non-commercial purposes as long as you provide attribution and offer any derivative works under a similar license.
3. On the toolbar above the map, hover over or click Dataset. Make sure that in the Model Projections column, the CMIP6 radio button is selected.
Provenance: IPCC WGI Interactive Atlas Reuse: This item is offered under a Creative Commons Attribution-NonCommercial-ShareAlike license http://creativecommons.org/licenses/by-nc-sa/3.0/ You may reuse this item for non-commercial purposes as long as you provide attribution and offer any derivative works under a similar license.
4. Next, hover over or click Variable in the toolbar. Beneath Atmosphere select Mean Temperature (T).
5. Hover over or click Quantity & Scenario in the toolbar. Confirm that beside Quantity, Change is selected. Then select Period: Medium-term (2041-2080) and Scenario: SSP3-7.0. Confirm that the Baseline remains 1850-1900 to be consistent with the other data you've looked at.
Provenance: IPCC WGI Reuse: This item is offered under a Creative Commons Attribution-NonCommercial-ShareAlike license http://creativecommons.org/licenses/by-nc-sa/3.0/ You may reuse this item for non-commercial purposes as long as you provide attribution and offer any derivative works under a similar license.
6. Click the shapes covering the contiguous US to bring up a time series graph of temperature for the selected area from 1950 to 2100 with the period displayed on the map highlighted with a gray square. Moving the cursor over the map will show the change in average temperature for that area on the temperature scale to the left of the map.
7. Once you have observed the changes in the time period 2041-2080, change the time period to Long-term (2081-2100).
Checking In
Consider projected changes where you live
On the map, click the area containing your home state or region to bring up a graph and see the predicted future changes in temperature.
Discuss
Put climate change in perspective by considering the following:
How old will you be in 2050, 2080?
How much will the temperature in most of the United States have changed by 2080?
Give several examples of how the increase in average temperature could impact your daily life.
Try the climate change questionnaire and learn more about scenarios
Read the article to the 9-question interactive, and answer the interactive's questions. Keep in mind that each choice you make will have costs for both the climate and for the pocketbooks of people under the policies. After you have completed the questionnaire, you will see a projection of climate and energy costs (from 2019 to 2100) based on your choices. Repeat the questionnaire several times and compare your results.
How did your choices affect the outcome?
Note: The black line in the results incorrectly labeled "Business as usual" depicts the high-emissions RCP8.5.
Discuss
How do individual lifestyle choices influence global climate change? Can one person really make a difference? Brainstorm and share ideas for changes in your lifestyle that you and your classmates and families can make.
Optional: more details about SRES and older scenarios
Hide
![[creative commons]](/images/creativecommons_16.png)
