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Breathtaking progress in crucial green technologies has brightened prospects for achieving the unprecedented emissions reductions needed to limit global warming to 1.5°C, as envisioned by the Paris climate agreement. But it will take a full restructuring of global energy and land-use systems, with the right mix of policy incentives. Decision-makers can rely on an increasing body of knowledge and experience to encourage the deployment of existing green technologies and speed the development of newer technologies.
Attaining a path toward 1.5°C would not only greatly reduce risks associated with climate change, it would also carry a number of important co-benefits, ranging from improved air quality to the modernization of infrastructure and economies to increased energy sector employment and jobs with better long-term prospects.
Given that carbon dioxide (CO 2 ) emissions remain in the atmosphere for hundreds of years, cumulative emissions of this greenhouse gas largely determine the resultant warming. That means the extent of near-term emissions reductions is more important than the exact year by which we reach zero. Achieving the 1.5°C target with medium likelihood requires emissions to decline immediately. The cheapest way to reach the 1.5°C target entails cutting emissions roughly in half by 2030 compared with 2020 levels.
The first key to these pathways is the electricity sector, which currently contributes roughly a third of total CO emissions (see chart). While electricity generation is still dominated by coal and gas, the addition of new capacity from wind and solar power increasingly outweighs fossil-fuel-based capacity gains.
The pandemic has shown that electricity systems tend to become cleaner with reduced demand, as higher-cost coal and gas power plants get switched off first, while solar, wind, nuclear, and hydro continue to generate as much electricity as can be taken up by the markets (Bertram and others 2021). Clearly, more efficient use of electricity can contribute significantly to swifter emission declines without sacrifcing system capacity. This will be especially valuable in the next decade, when a large share of electricity generation will still come from carbon-intensive fossil fuels.
Increased efficiency in liquid, solid, and gaseous fuel consumption by industry, transportation, and buildings is even more crucial, because gains in efficiency lead to immediate emission reductions.
Limited availability of clean power technology is no longer an impediment to the decarbonization of electricity—solutions for integration are also improving—but the slow phaseout of fossil-fuel-based capacities is. Regulation of greenhouse gas emissions, ideally via some form of carbon pricing, is necessary to shift new investments to green power technology and create incentives for phasing out power plants. If the global community is successful in seizing the opportunity offered by rapid power system decarbonization, the power sector can slash its emissions by more than two-thirds by 2030, as shown in the Net Zero 2050 scenario in the chart.
What about land use and achieving net zero emissions? The land sector currently includes both CO sinks (uses that take carbon out of the atmosphere, such as establishing new forests) and CO2 sources, most notably deforestation but also other land-use processes. Changes in land-use practices could even achieve CO neutrality in that sector by 2030 (though land use—chiefly agriculture—will inevitably continue to contribute to warming through methane and nitrous oxide emissions).
This leaves energy demand from industry, buildings, and transportation as the primary contributors of fossil-fuel-based CO emissions in 2030 and beyond in scenarios in line with the 1.5°C target. In these scenarios, the combined emissions of these sectors would need to be more than halved by 2040 and to reach about a quarter of today’s levels by 2050 in order to achieve carbon neutrality around that date.
Compensating for even this comparatively low level of residual emissions requires a very fast and challenging expansion of CO removal options, such as planting new forests, direct air capture— capturing CO from the atmosphere and then storing it geologically—and bioenergy with carbon capture and storage, or BECCS, technologies that produce clean energy from biomass while also capturing and permanently storing CO.
Many of the technologies required to decarbonize the demand sectors involve direct or indirect electrification via hydrogen-based fuels, such as fuel cell technology and synthetic fuels (Ueckerdt and others 2021). Moreover, these technologies are not yet deployed at scale in markets and will likely face institutional and environmental challenges. Their future performance and costs are thus considerably more uncertain than those of technologies deployed today (for example, renewable energy and battery-electric vehicles).
There are options for realizing a net zero global energy system in which all carbon added to the atmosphere is offset by carbon removed.
This uncertainty implies that there are various options for realizing a net zero global energy system, one in which all carbon added to the atmosphere is offset by carbon removed. If all these options develop more favorably than expected, it may also be possible (and worthwhile) to achieve stronger net negative emissions (removing more carbon than is added), thus lowering global mean temperature after its peak. If some technology options develop faster than expected, while others lag behind, the balance of options may be different than projected, but the overall net zero goal is still achievable. Only if all options develop more slowly than expected—or if unforeseen hurdles or bottlenecks cannot be overcome (for example, bioenergy-related sustainability issues)—would achievement of net zero energy systems be much more difficult than currently projected.
Bauer, Nico, Christoph Bertram, Anselm Schultes, David Klein, Gunnar Luderer, Elmar Kriegler, Alexander Popp, and Ottmar Edenhofer. 2020. “Quantifcation of an Efficiency-Sovereignty Trade-of in Climate Policy.” Nature 588 (7837): 261–66.
Bertram, Christoph, Gunnar Luderer, Felix Creutzig, Nico Bauer, Falko Ueckerdt, Aman Malik, and Ottmar Edenhofer. 2021. “COVID-19-Induced Low Power Demand and Market Forces Starkly Reduce CO2 Emissions.” Nature Climate Change 11 (3): 193–96.
Ueckerdt, Falko, Christian Bauer, Alois Dirnaichner, Jordan Everall, Romain Sacchi, and Gunnar Luderer. 2021. “Potential and Risks of Hydrogen-Based e-Fuels in Climate Change Mitigation.” Nature Climate Change 11 (5): 384–93.