Without any emission controls, carbon dioxide concentrations in the atmosphere doubled by 2100. By design, RCP 4.5 limits them to about 35 percent higher than 2005 levels.
The conditions to limit emissions did not specify how to go about doing that, only that carbon from all sources had economic value. Under limiting conditions, carbon dioxide prices rose steadily until they reached $85 per ton of carbon dioxide by 2100, in 2005 dollars.
In the scenario, the price of carbon stimulated a rise in nuclear power and renewable energy use. Also, it became cheaper to implement technologies that capture and store emissions from fossil- and bio-fuel based electricity than to emit carbon dioxide. Buildings and industry became more energy efficient and used cleaner electricity for their energy needs.
Additionally, carbon dioxide emissions from man-made sources peaked around 2040 at 42 gigatons per year (currently, emissions are at 30 gigatons per year), decreased with about the same speed as they rose, then levelled out after 2080 at around 15 gigatons per year.
Also, the team converted the results of the scenario to match the resolution of the climate models that are using the results. That way, scientists can more easily integrate RCP 4.5 with climate models. Economies, for example, occur on national scales, but chemical reactions of gas in the air occur in much smaller spaces.
This change in scale to accommodate climate models reveals important regional details. For example, although globally methane emissions change little over the century, their geographic origins shift around. As the century wears on, South America and Africa put out more methane and the industrialized nations less.
|Contact: Mary Beckman|
DOE/Pacific Northwest National Laboratory