Climate Policy

Accounting for nearly one-third of the global land surface, forests help regulate the climate and protect watersheds while providing consumer products and outdoor experiences that enhance the quality of life. Climate change will inevitably influence forests’ ability to deliver these services, but past studies have provided a limited picture of what changes may come this century. Now researchers from the Corvallis Forestry Sciences Laboratory, MIT, Ohio State University and the U.S.

The future of forests under climate change
Climate Stabilization at 2°C and Net Zero Carbon Emissions

The goal to stabilize global average surface temperature at lower than 2°C above pre-industrial level has been extensively discussed in climate negotiations. A number of publications state that achieving this goal will require net anthropogenic carbon emissions (defined as anthropogenic emissions minus anthropogenic sinks such as carbon capture and sequestration and reforestation) to be reduced to zero between years 2050 and 2100. At the same time, it is also shown in the literature that decreases of non-CO2 emissions can significantly affect the allowable carbon budget. In this study, we explore possible emission pathways under which surface warming will not exceed 2°C, by means of emission-driven climate simulations with an Earth System Model of Intermediate Complexity linked to an Economic Projection and Policy Analysis Model. We carried out a number of simulations from 1861 to 2500 for different values of parameters defining the strength of the climate system response to radiative forcing and the strength of the natural carbon sources and sinks under different anthropogenic emission projections. Although net anthropogenic emissions need to be reduced to zero eventually to achieve climate stabilization, the results of our simulations suggest that, by including significant reductions in non-CO2 emissions, net carbon emissions do not have to be zero by 2050 or even 2100 to meet the 2°C target because of offsets due to the natural carbon sinks in the oceans and terrestrial ecosystems. We show that net anthropogenic carbon emissions falling from today’s 9.5 GtC/year to 2.5–7 GtC/year by 2050 and then to 1–2.8 GtC/year by 2100 are consistent with a 2°C target for a range of climate sensitivities (2.0–4.5°C) similar to the IPCC likely range. Changes in the surface temperature beyond 2100 depend on the emission profiles after 2100. For post-2100 carbon emissions decreasing at a rate of about 1.5% per year along with continued decreases in non-CO2 emissions, our projections indicate that natural ecosystems will be able to absorb enough carbon to prevent surface temperature from rising further. A major reason for our results is that the land and ocean uptake rates are a function of the total atmospheric CO2 concentration and, due to the very long lifetime of CO2, this does not decrease anywhere near as fast as the imposed CO2 emissions. The required mixes of energy technologies and the overall costs to achieve the 2°C target are highly dependent on the assumptions about the future costs of low-carbon and zero-carbon emitting technologies. In all our projections, the global energy system requires substantial transformations in a relatively short time.

More than 600 acres of solar panels have been successfully installed and connected on land in North Carolina and are delivering their power into the nation’s grid, thanks to a power purchase agreement (PPA) with MIT and two other Boston-based organizations. The installation will not only offset a substantial portion of the Institute’s greenhouse gas emissions but also enable an exceptional level of real-time data collection that could enhance research and education on the design and operation of solar facilities.

MIT’s solar plant is delivering on its promises
The role of atmospheric oxidation in recent methane growth

The growth in global methane (CH4) concentration, which had been ongoing since the industrial revolution, was observed to stall around the year 2000, before resuming globally in 2007. Here, we evaluate the role of the hydroxyl radical (OH), the major CH4 sink, in the recent CH4 growth. We also examine the influence of systematic uncertainties in OH on CH4 emissions inferred from atmospheric observations. We use observations of 1,1,1-trichloroethane (CH3CCl3), which is lost primarily through reaction with OH, to estimate OH levels as well as CH3CCl3 emissions, whose uncertainty has previously limited the accuracy of OH estimates. We find a 61% - 73% probability that a decline in OH has contributed to the post-2007 methane rise. Our median solution suggests that CH4 emissions increased relatively steadily during the late 1990s and early 2000s, after which, growth was more modest. This solution obviates the need for a sudden, statistically significant change in total CH4 emissions around the year 2007 to explain the atmospheric observations, and contributes to the decline in the atmospheric 13CH4/12CH4 ratio. Our approach indicates that significant OH-related uncertainties in the CH4 budget remain, and we find that it is not possible to implicate, with a high degree of confidence, rapid global CH4 emissions changes as the primary driver of recent trends, when our inferred OH trends and these uncertainties are considered.

Hedging Strategies: Electricity Investment Decisions under Policy Uncertainty

Given uncertainty in long-term carbon reduction goals, how much non-carbon generation should be developed in the near-term? This research investigates the optimal balance between the risk of overinvesting in non-carbon sources that are ultimately not needed and the risk of underinvesting in non-carbon sources and subsequently needing to reduce carbon emissions dramatically. We employ a novel framework that incorporates a computable general equilibrium (CGE) model of the U.S. into a two-stage stochastic approximate dynamic program (ADP) focused on decisions in the electric power sector. We solve the model using an ADP algorithm that is computationally tractable while exploring the decisions and sampling the uncertain carbon limits from continuous distributions.

The results of the model demonstrate that an optimal hedge is in the direction of more non-carbon investment in the near-term, in the range of 20-30% of new generation. We also demonstrate that the optimal share of non-carbon generation is increasing in the variance of the uncertainty about the long-term carbon targets, and that with greater uncertainty in the future policy regime, a balanced portfolio of non-carbon, natural gas, and coal generation is desirable.

After more than three and a half years of service as the 13th U.S. Secretary of Energy, nuclear physicist Ernest J. Moniz has returned to his roots at MIT, the place where he served most of his professional career.

Nominated to the cabinet by President Barack Obama in March 2013 and confirmed by the Senate on May 16 in a unanimous vote — a rare occurrence in a polarized political atmosphere — Moniz left the office on Jan. 20, 2017, with the arrival of the Trump administration.

Celebrating the homecoming of Ernest Moniz
Assessing climate change impacts, benefits of mitigation, and uncertainties on major global forest regions under multiple socioeconomic and emissions scenarios

We analyze a set of simulations to assess the impact of climate change on global forests where MC2 dynamic global vegetation model (DGVM) was run with climate simulations from the MIT Integrated Global System Model-Community Atmosphere Model (IGSM-CAM) modeling framework. The core study relies on an ensemble of climate simulations under two emissions scenarios: a business-as-usual reference scenario (REF) analogous to the IPCC RCP8.5 scenario, and a greenhouse gas mitigation scenario, called POL3.7, which is in between the IPCC RCP2.6 and RCP4.5 scenarios, and is consistent with a 2ºC global mean warming from pre-industrial by 2100. Evaluating the outcomes of both climate change scenarios in the MC2 model shows that the carbon stocks of most forests around the world increased, with the greatest gains in tropical forest regions. Temperate forest regions are projected to see strong increases in productivity offset by carbon loss to fire. The greatest cost of mitigation in terms of effects on forest carbon stocks are projected to be borne by regions in the southern hemisphere. We compare three sources of uncertainty in climate change impacts on the world's forests: emissions scenarios, the global system climate response (i.e., climate sensitivity), and natural variability. The role of natural variability on changes in forest carbon and net primary productivity (NPP) is small, but it is substantial for impacts of wildfire. Forest productivity under the REF scenario benefits substantially from the CO2 fertilization effect and that higher warming alone does not necessarily increase global forest carbon levels. Our analysis underlines why using an ensemble of climate simulations is necessary to derive robust estimates of the benefits of greenhouse gas mitigation. It also demonstrates that constraining estimates of climate sensitivity and advancing our understanding of CO2 fertilization effects may considerably reduce the range of projections.

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