Limiting temperature increase to 3.0°C (or lower) in 2100 requires action, and estimates by experts saying that the new Business as Usual (BAU) is 3.0°C assume global action. You can use En-ROADS to determine what action is necessary.


First, read this FAQ about why the En-ROADS BAU goes up to 4.1 degrees C by 2100.


The En-ROADS BAU scenario answers the question, “What might the world look like if we don’t take action on climate?” It simulates a world without any new energy or climate actions. This is different from some other models’ baseline scenarios, and it is important to keep this distinction in mind. We chose to construct the En-ROADS BAU scenario in this way because “pledged” or “announced” policies can be altered. Governments change and priorities shift. There is abundant academic literature supporting that without action, we are headed to around 4°C of warming by 2100. Many of those scenarios can be found in this FAQ.


The En-ROADS BAU does not include countries’ Nationally Determined Contributions (NDCs), for instance. Under the Paris Agreement, countries submit plans, known as NDCs, to limit their greenhouse gas emissions. We have chosen not to include these pledges in the En-ROADS BAU. Instead, you can use En-ROADS yourself to simulate the effects of NDCs and other policy actions by comparing your scenario to the BAU scenario in which those policy actions are not taken. 


Other models may include some climate action in their scenarios, and the terminology can get confusing. The International Energy Agency’s (IEA) World Energy Outlook 2019, for example, includes three scenarios: a Current Policies Scenario, a Stated Policies Scenario, and a Sustainable Development Scenario. The Stated Policies Scenario includes NDCs and other announced plans and policy intentions, while the Current Policies Scenario includes only those government policies and measures that have been adopted (though not necessarily enacted) by mid-2019 (and does not include NDCs). Scenarios that include NDCs are sometimes referred to as “current policies,” which can be confusing. Scenarios leading to 3°C by 2100 generally incorporate NDCs.


So yes, we may be headed to 3°C by 2100, rather than 4°C, as a result of current policy goals. You can use En-ROADS to determine what action is necessary to get there. What do countries around the world need to do in order to deliver on these stated policies? And then, you can explore what is needed to get to 2°C and below.