Global Emissions Scenarios
What will life on Earth be like over the next 100 years?
No one knows the answer.
There are many possibilities depending on population growth, technological change, the pace of economic development and other factors about which we are uncertain. So, scientists develop scenarios to explore different possibilities. A scenario makes plausible assumptions about key drivers and allows us to explore what might happen if the assumptions are correct. Sometimes people talk about “what-if” scenarios, or “if-then” scenarios—if the assumptions hold, then specific outcomes would be expected. Different assumptions lead to different scenarios.
For example, one scenario examines the possibility that we behave much like we do now. This is called the business-as-usual scenario. It assumes that all the key drivers would continue; growth trends of the past are projected into the future. So for this future scenario the production of greenhouse gases is expected to continue to rise and drive changes in climate.
In science, a prediction tells how likely something is to occur. A projection describes a possibility -- if particular conditions exist, then what would occur. But a projection does not describe how likely it is to occur, so a projection is not a prediction. An “if-then” scenario is a projection.
Think globally! How will we be using energy, for example, over the next hundred years? Will we be more or less dependent on fossil fuels? What is the scenario? Now think locally! If this scenario happens, consider how life where you live might change. Are there things you might like to do differently?
While we do not know what will happen, we can study plausible scenarios to understand who and what might be affected. This website is intended to help you understand how global change might affect regional and local land use and climate. For example, you can
1) examine two global emissions scenarios to get a better idea about possible changes in greenhouse gases and other pollutants in the atmosphere and the potential repercussions for a region’s climate.
2) study current local and regional trends in population, energy use, land use, the economy and other factors to get a sense of how they might develop over time in a changing climate.
The CARA website relies on two global scenarios most commonly used by the Inter-governmental Panel on Climate Change (IPCC) called A2 and B2. The figure shows the differences in assumptions about their driving factors.
A2 assumes high population growth and energy use, slow technological progress, and a regional focus.
B2 assumes moderate population growth and energy use, moderate technological progress, and a local focus.
Both A2 and B2 assume moderate economic growth.
For more details, go to: Climate Change Scenarios and Projections
Projected global greenhouse gas emissions (left) and concentration levels (right) for 2000 to 2100 using “SRES” global scenarios.
This is Figure 3.12a from the Third Assessment Report. Data for this figure can be found at http://www.grida.no/climate/ipcc_tar/wg1/521.htm; on the right is Figure 3.12b from the Third Assessment Report. Data for this figure can be found at http://www.grida.no/climate/ipcc_tar/wg1/531.htm.