JP

Is there warming in the pipeline? A multi-model analysis of the Zero Emissions Commitment from CO2

Abstract: The Zero Emissions Commitment (ZEC) is the change in global mean temperature expected to occur following the cessation of net CO2 emissions and as such is a critical parameter for calculating the remaining carbon budget. The Zero Emissions Commitment Model Intercomparison Project (ZECMIP) was established to gain a better understanding of the potential magnitude and sign of ZEC, in addition to the processes that underlie this metric. A total of 18 Earth system models of both full and intermediate complexity participated in ZECMIP. All models conducted an experiment where atmospheric CO2 concentration increases exponentially until 1000 PgC has been emitted. Thereafter emissions are set to zero and models are configured to allow free evolution of atmospheric CO2 concentration. Many models conducted additional second-priority simulations with different cumulative emission totals and an alternative idealized emissions pathway with a gradual transition to zero emissions. The inter-model range of ZEC 50 years after emissions cease for the 1000 PgC experiment is −0.36 to 0.29 ∘C, with a model ensemble mean of −0.07 ∘C, median of −0.05 ∘C, and standard deviation of 0.19 ∘C. Models exhibit a wide variety of behaviours after emissions cease, with some models continuing to warm for decades to millennia and others cooling substantially. Analysis shows that both the carbon uptake by the ocean and the terrestrial biosphere are important for counteracting the warming effect from the reduction in ocean heat uptake in the decades after emissions cease. This warming effect is difficult to constrain due to high uncertainty in the efficacy of ocean heat uptake. Overall, the most likely value of ZEC on multi-decadal timescales is close to zero, consistent with previous model experiments and simple theory.

Will using newer input-output data for general equilibrium modeling provide a better estimate for the CO2 mitigation cost?

Summary: Large-scale economy-wide equilibrium models are widely used for assessing energy or climate policies. As different models often produce diversified outcomes for similar policies, researchers have been trying to understand reasons behind this observation, including cost assumptions for mitigation options, model structure, policy design, and timing. In this study, we focus on analyzing how updating the input-output database of a CGE model could inadvertently change the model output, which has not been carefully examined but could also be an important source that accounts for variations in simulation results of distinct models.

To answer the research question, we provide an analytical framework that elucidates how using a database with a higher energy price raises the CO2 mitigation cost when the substitution between inputs is relatively limited in the short-run, or when the price hike is considered as temporary. We also provide a numerical example for the analysis, and propose an adjustment that could, under the same percentage reduction in emissions, address the concerns of using the input-output data with prices for fossil fuels and their consumption levels deviating from a more sustainable state.

Biomagnification of methylmercury in marine plankton ecosystems

Abstract: Methylmercury is greatly bioconcentrated and biomagnified in marine plankton ecosystems, and these communities form the basis of marine food webs. Therefore, the evaluation of the potential exposure of methylmercury to higher trophic levels, including humans, requires a better understanding of its distribution in the ocean and the factors that control its biomagnification. In this study, a coupled physical/ecological model is used to simulate the trophic transfer of monomethylmercury (MMHg) in a marine plankton ecosystem. The model includes phytoplankton, a microbial community, herbivorous zooplankton (HZ), and carnivorous zooplankton (CZ). The model captures both shorter food chains in oligotrophic regions, with small HZ feeding on small phytoplankton, and longer chains in higher nutrient conditions, with larger HZ feeding on larger phytoplankton and larger CZ feeding on larger HZ. In the model, trophic dilution occurs in the food webs that involve small zooplankton, as the grazing fluxes of small zooplankton are insufficient to accumulate more MMHg in themselves than in their prey. The model suggests that biomagnification is more prominent in large zooplankton and that the microbial community plays an important role in the trophic transfer of MMHg. Sensitivity analyses show that with increasing body size, the sensitivity of the trophic magnification ratio to grazing, mortality rates, and food assimilation efficiency (AEC) increases, while the sensitivity to excretion rates decreases. More predation or a longer zooplankton lifespan may lead to more prominent biomagnification, especially for large species. Because lower AEC results in more predation, modeled ratios of MMHg concentrations between large plankton are doubled or even tripled when the AEC decreases from 50% to 10%. This suggests that the biomagnification of large zooplankton is particularly sensitive to food assimilation efficiency.

Featuring a presentation by Joint Program Deputy Director Sergey Paltsev on scaling up low-carbon energy.

The energy sector is facing unprecedented challenges, with the global Covid-19 pandemic complicating an already challenging transition toward a low-carbon future. One of the key elements in addressing both the current pandemic and climate change is with forward-looking collaborations in technology development and innovation—which have long been a hallmark of MIT’s approach to problem solving.

Scaling up low-carbon energy: Economic, geopolitical, and environmental impacts

The financial community has become increasingly concerned with two types of threats to financial and economic systems driven by climate change and efforts to alleviate it: physical risk—exposure to climate and/or weather extremes, and transition risk—the potential for fossil fuel assets to lose value in a rapid transition to a low-carbon economy.

Bank of Canada: Climate change and energy transition pose substantial economic risks
Impacts of climate change policies worldwide on the Russian economy

Abstract: Because the Russian economy relies heavily on exports of fossil fuels, the primary source of human-induced greenhouse gas (GHG) emissions, it may be adversely impacted by Paris Agreement-based climate policies that target reductions in GHG emissions. Applying the MIT Economic Projection and Policy Analysis (EPPA) model to assess the impacts on the Russian economy of the efforts of the main importers of Russian fossil fuels to follow the global goals of the Paris Agreement, we project that climate-related actions outside of Russia will lower the country’s GDP growth rate by about one-half of a percentage point. The Paris Agreement is also expected to raise Russia’s risks of facing market barriers for its exports of energy-intensive goods, and of falling behind in the development of low-carbon energy technologies that most of the world is increasingly adopting.  

Key policy insights:

  • Regardless of its domestic emissions reduction efforts, Russia will not be able to sustain its current trajectory of fossil fuel export-based development due to climate policies worldwide.
  • To address the challenge of climate-related energy transition, Russia needs a new comprehensive development strategy that accounts for the post-Paris Agreement global energy landscape.
  • The key elements of such a strategy include diversification of the economy, moving to low-carbon energy sources, and investing in human capital development.
  • Our diversification scenarios show that redistribution of income from the energy sector to the development of human capital would benefit the economy.
  • The largest impact of investment re-orientation from the fossil fuel sector would be on manufacturing, services, agriculture and food production.

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