Abstract: We assess the contribution of India’s hard-to-abate sectors to the country’s current emissions and their likely future trajectory of development under different policy regimes. We employ an enhanced version of the MIT Economic Projection and Policy Analysis (EPPA) model to explicitly represent the following hard-to-abate sectors: iron and steel, non-ferrous metals (copper, aluminum, zinc, etc.), non-metallic minerals (cement, plaster, lime, etc.), and chemicals.

We find that, without additional policies, the Paris Agreement pledges made by India for the year 2030 still can lead to an increasing use of fossil fuels and corresponding greenhouse gas (GHG) emissions, with projected CO2 emissions from hard-to-abate sectors growing by about 2.6 times from 2020 to 2050. Scenarios with electrification, natural gas support, or increased resource efficiency lead to a decrease in emissions from these sectors by 15-20% in 2050, but without carbon pricing (or disruptive technology changes) emissions are not reduced relative to their current levels due to growth in output. Carbon pricing that makes carbon capture and storage (CCS) economically competitive is critical for achieving substantial emission reductions in hard-to-abate sectors, enabling emission reductions of 80% by 2050 relative the scenario without additional policies.

Without substantial government support, decarbonization of India’s hard-to-abate sectors will not be achievable.

Plain Language Summary: The ocean has absorbed roughly 40% of fossil fuel carbon dioxide (CO₂) emissions since the beginning of the industrial era. This so-called “ocean carbon sink,” which primarily sequesters emissions in the form of dissolved inorganic carbon (DIC), plays a key role in regulating climate and mitigating global warming. However, we still lack a mechanistic understanding of how physical, chemical, and biological processes impact the ocean DIC reservoir in both space and time, and hence how the storage rates of emissions may change in the future.

Here we use a global-ocean biogeochemistry model Estimating the Circulation and Climate of the Ocean-Darwin, which ingests both physical and biogeochemical observations to improve its accuracy, to map how ocean circulation, air-sea CO₂ exchange, and marine ecosystems have modulated the combined natural and anthropogenic ocean DIC budget for 1995–2018. We find that in the upper ocean, circulation provides the largest supply of DIC while biological processes drive the largest loss. Year-to-year changes in the ocean carbon sink are dominated by El Niño-Southern Oscillation events in the equatorial Pacific Ocean, which then affect DIC globally.

In summary, our data-constrained, global-ocean DIC budget constitutes a significant step forward toward understanding climate-related changes to the ocean DIC reservoir.