Introduction
The graphs available on this part of the web tool show the differences between the climate scenarios developed using A2 estimates of greenhouse gasses and the scenarios developed using B2 estimates of greenhouse gasses. To help interpret these graphs, please click on the topics listed on the screen. We encourage you to view the topics listed in the order shown.
Essentials:
Histograms of projected climate change for the A2 and B2 emissions scenarios are available for the early century period (defined as 2010-2029), the mid-century period (defined as 2040-2059), and late-century period (defined as 2080-2099). On the plots, the darker color represents the scenarios developed using the A2 emissions scenarios, and the lighter color refers to the scenarios developed using the B2 emissions scenarios. Thus, for the early century period the dark green and light green colors refer to the A2 and B2 scenarios, respectively. For the mid century period the A2 scenarios are shown in dark blue and the B2 scenarios in light blue, and for the late century the A2 scenarios are seen in dark red and the B2 in light red. The histograms are interpreted similarly to the other histograms available as part of this tool. The example shown here is the projected change in the median number of growing degree days (base 41ºF) per year for the mid century period. The horizontal axis gives the projected change in the median number of growing degree days compared to a “control” period. The control period is defined as 1990-2009 and is used to represent present-day conditions. The projected change was found by subtracting for each climate scenario the simulated median number of growing degree days for the control period from the simulated median number of growing degree days for the future period. The values along the horizontal axis are the midpoints for the categories. For example, 0 is the midpoint of the category ranging from -50 to 50 growing degree days and so on. The vertical axis shows the number of scenarios that projected a certain change. For East Jordan, four of the B2 scenarios project an increase in the median value of growing degree accumulation of 50 to 150 Growing Degree Days by 2040-2059, and 16 of the A2 scenarios project an increase of 350 to 450 Growing Degree Days. If you click on the box to the right of the graph, the average projected value for the A2 and B2 scenarios is displayed. For the this example, the average values for the B2 scenarios is 336 growing degree days and the average value for the A2 scenarios is 354 growing degree days.
A2 vs B2
A2 estimates represent a world where the underlying theme is self-reliance and preservation of local identities, where the population is continuously increasing, and where economic development is regionally focused. For the A2 estimates, greenhouse gases continue to increase throughout the century reaching approximately 800 parts per million (ppm) by the end of the century. In contrast, the B2 estimates represent a world in which the emphasis is on local solutions to economic, social and environmental sustainability. Although the population increases at a lower rate than for the A2 estimates, the technological change is less rapid and more diverse. Carbon dioxide stabilizes around 650 parts per million (ppm).
Interpreting Future Changes
For the early and mid century periods, the difference between the A2 and B2 scenarios is not as large as for the late century period. This is because the two emissions estimates do not diverge until approximately 2020. By the end of the century, the A2 and B2 greenhouse gas estimates differ considerably.