This Heritage Foundation calculator is an online tool that lets the public simulate how carbon dioxide (CO2)-reduction policies pursued by lawmakers and the Biden Administration will affect global temperatures. It is inspired by a similar online tool that the Cato Institute had published and decommissioned.
The calculator is based on the Intergovernmental Panel on Climate Change’s (IPCC’s) Model for Assessment of Greenhouse Gas Induced Climate Change (MAGICC). As the documentation illustrates, this model has myriad assumptions about climate. The Climate Calculator focuses on two key assumptions: climate sensitivity and the level of emissions reduction. Scientists generally agree that the Earth’s temperature warms as CO2 emissions increase—the real question is to which degree (no pun intended).
Climate sensitivity measures how much the Earth’s temperature will warm as a result of a doubling of atmospheric CO2 concentration. The emissions-reduction level is the percentage of CO2 emissions that lawmakers would seek to reduce with respect to current emissions. The methodology below contains full details.
The simulations presented in this calculator allow user-selected climate sensitivities between 2℃ and 5℃, stated as the “very likely” range of climate sensitivity according to the IPCC’s Sixth Assessment Report, encompassing the “likely” range of 2.5℃ to 4℃. Although empirical evidence comparing observations to predictions suggests that sensitivities at the lower end of these ranges may indeed be more plausible, Heritage’s Climate Calculator allows users to decide which climate sensitivity they would like to assume and how steep of a reduction in fossil fuel use they would like to see. The results speak for themselves—regardless of the assumptions, the climate impact of CO2–reduction policies is slim to none!
Projected Global Temperature Changes
with respect to 2010 levels
Without Carbon Reduction
With Carbon Reduction
Effect of Carbon Reduction
Design and Development: Calculator produced by Christina Hamm and Jay Simon. Data compiled by Kevin Dayaratna.
Methodology
The analysis in this calculator uses the Model for the Assessment of Greenhouse Gas Induced Climate Change (MAGICC) version 6. MAGICC quantifies the relationship among atmospheric radiative forcing, oceanic heat content, and surface temperature perturbation via the following relationship:
\[ΔQ_G=λGΔT_G+\frac{dH}{dt},\]
where \(ΔQ_G\) is the global-mean radiative forcing at the top of the troposphere. This extra energy influx is decomposed into increased outgoing energy flux and heat content changes in the ocean via the derivative \(\frac{dH}{dt}\). The outgoing energy flux is related to the global-mean feedback factor \(λ_G\) as well as surface temperature perturbation \(ΔT_G\).
Climate sensitivity, denoted in the MAGICC model as \(ΔT_{2x}\), is defined as the equilibrium global-mean warming after a doubling of CO2 concentrations and specified via a reciprocal relationship to a feedback factor \(λ\):
\[ΔT_{2x}=\frac{ΔQ_{2x}}{λ}\]
In the above equation, \(ΔT_{2x}\) represents the climate sensitivity and \(ΔQ_{2x}\) represents the radiative forcing following a doubling of \(CO_2\) concentrations. The time-dependent or state-dependent effective climate sensitivity \(S^t\) is defined by combining the above two equations as follows:
\[S^t=\frac{ΔQ_{2x}}{λ^t}=ΔQ_{2x}\frac{ΔT_G^t}{ΔQ^t-\frac{dH}{dt}|^t},\]
where \(ΔT_{2x}\) represents the model-specific forcing for doubled CO2 concentration, \(λ_t\) represents the time-specific feedback factor, \(ΔQ^t\) represents the radiative forcing, \(ΔT_G^t\) represents the global-mean temperature perturbation, and \(\frac{dH}{dt}|^t\) represents the climate system’s heat uptake at time t.
MAGICC also contains a carbon-cycle model that incorporates temperature feedback effects. One of the a priori specifications pertaining to this model is a greenhouse gas emissions (GHG) scenario. In Center for Data Analysis (CDA) simulations (results embedded in this Climate Calculator), CDA modelers used and modified Representative Concentration Pathway 6.0 (RCP6), provided as a potential baseline emissions scenario within the model.
Using data from the Organization for Economic Co-operation and Development (OECD), the CDA estimated that the United States and European Union emitted approximately 43 percent and 23 percent of CO2 emissions, respectively, of all OECD member nations. In CDA simulations, modelers altered OECD projections accordingly, assuming this fraction to be constant over time, beginning in 2020. The results thus overstate the estimated temperature impact of the modeled GHG-reduction policy.