Scientists use computer climate models as a way to understand how the climate has behaved in the past and how it is likely to change in the future. Scientists use different scenarios to allow them to evaluate all the different future possibilities for the climate. The United Kingdom Met Office Hadley Centre has created two datasets for Science On a Sphere, using two different scenarios. The first scenario, A1B-IMAGE, assumes a "business-as-usual" path forward in the future with continually increasing carbon dioxide rates. In this scenario, CO2 rises to 774ppm by 2099 and the global mean temperature increases by 4.41°C. The second scenario, E1, is an aggressive mitigation scenario that includes reduced fossil fuel use with the goal of keeping global mean warming below 2°C. In the E1 scenario, carbon dioxide increases to 435ppm by 2050 and then drops to 421ppm by 2099, with a global mean temperature increase of 2.12°C.
These datasets start in the year 1860, when carbon dioxide concentrations were 286ppm. Areas that are shades of blue are cooler than the year 2000 and areas that are shades of red are warmer than the year 2000. Both scenarios highlight the fact that the temperature changes can vary widely by region. By comparing these two datasets, it's possible to see the difference that carbon dioxide concentrations make on global temperatures. The reduced emissions of the E1 scenario lead to cooler temperatures than those found in the A1B-IMAGE scenario. The E1 scenario also demonstrates that while the atmosphere does respond positively to reduced emissions, it takes several decades. According to scientists, in order to take the path of the E1 scenario in the future, carbon dioxide emissions must peak before 2020, followed by a rapid decline to near zero by 2100. For more information about the models and results, visit: http://www.springerlink.com/content/x456511l86137um4/