What is our assessment?

Based on our analysis, deploying electric irrigation pumps will reduce emissions but will not provide a globally significant climate impact (>0.1 Gt CO₂‑eq/yr ), even under high adoption scenarios, until electrical grid emissions decline further. Therefore, this potential climate solution is “Worthwhile.”

What is it? 

This solution reduces emissions from irrigation by replacing pumps powered by natural gas, diesel, propane, or gasoline with electric pumps. Irrigation is the practice of adding water to croplands or pastures to reduce crop water stress and increase productivity. Pumps are used on some irrigated croplands to extract groundwater, transport surface water, and pressurize water for application through sprinklers or drip irrigation systems. Electric pumps have much higher motor efficiencies (~88%) than fossil fuel pumps (~21–31%), so pump switching reduces the energy required to pump the same amount of water. The extent to which emissions are reduced depends on the emissions intensity of the electrical grid mix. Electric pumps reduce emissions when the emissions intensity of the grid is below ~0.75 kg CO₂‑eq /kWh, or when they are powered by on-site solar or wind energy. In some places, additional emissions reductions can be achieved through Improving Irrigation Water Use Efficiency.

Does it work?

The efficiency and emissions benefits of electric pumps over fossil fuel pumps are well established. On-farm pumping emissions, currently estimated at approximately 0.2 Gt CO₂‑eq/yr, could feasibly be eliminated if all fossil fuel pumps are replaced with electric pumps and electrical grid emissions reach net-zero, or if they are powered by on-farm solar or wind energy. However, the climate impact of electric pump adoption today would be much lower, as electricity generation still produces substantial emissions. Under current conditions, replacing a diesel pump with an electric pump will reduce emissions in most, but not all, places around the world.

Why are we excited?

Electric pumps can reliably reduce emissions, are already cost-competitive and widely used, and adoption is increasing. Irrigation is a major energy user, and its energy use is increasing as irrigated areas expand. These trends are expected to continue in the coming decades as climate change exacerbates heat and water stress and agricultural production intensifies in low- and middle-income countries. Coupled with ongoing reductions in electrical grid emissions intensity, the potential climate benefits of this solution are growing.

Electric pump adoption can also be geographically targeted, as just five countries (China, India, the United States, Pakistan, and Iran) account for almost 70% of irrigation energy use. Areas with high groundwater reliance can also be targeted, as groundwater pumping accounts for 89% of irrigation energy use.

Pump switching also provides additional benefits, such as lowering long-term energy costs for farmers and reducing air pollution from on-farm fossil fuel use. Access to the electrical grid is the primary technical barrier to electric pump adoption, but small-scale solar installations can be used where grid connectivity is limited. Powering pumps with on-site solar also eliminates operational emissions, reduces the load on the electrical grid, and insulates farmers from variability in energy costs. 

Why are we concerned?

The climate impacts of pump switching are highly dependent on the emissions factor of the electrical grid. A large share of the potential reduction in fossil fuel pumping is located in India and China, which currently have relatively high electrical grid emissions intensities. Under the current grid mix, we estimate that pump switching in these countries will result in only modest benefits or a small increase in emissions.

What is our assessment?

Advanced geothermal systems (AGS) are emerging as one of the most promising technologies for reliable, utility-scale, zero-carbon energy that can complement wind and solar, strengthening grid resilience, and providing heat for district heating and industrial uses. The technology, which is built on an existing base of technical and industrial expertise and capacity, is advancing rapidly through major R&D efforts, pilot projects and, just recently, small scale commercial operations. While large-scale deployment is still in its early stages and challenges remain around cost, execution, and social acceptance, we expect meaningful progress by the 2030s. For now, we will “Keep Watching” this solution.

What is it?

Advanced geothermal systems (AGS) are a suite of renewable energy technologies that extract heat from deep within the Earth’s crust to generate electricity, provide high-temperature heat for industrial processes or district heating, and enable geothermal energy storage by storing heat underground. Unlike traditional geothermal systems that tap naturally occurring hot water or steam reservoirs, such as geysers or volcanic areas, AGS access geothermal heat by drilling into the earth, injecting and circulating water (or other fluids) through hot, dry rock formations underground, and then recovering the heated fluid or steam to generate electricity before reinjecting it back underground. Circulation of the water between the surface and the geothermal reservoir can be a in closed loop system, where the water or other fluid is contained within pipes throughout the heat exchange circulation cycle, or in an open loop, enhanced geothermal system (EGS) where the subsurface rocks are hydraulically fractured, or “fracked,” to increase permeability and allow water to flow between an injection well and a production well.

Does it work?

Electricity and heat production by an advanced geothermal power plant emits virtually no greenhouse gases. Analysis by the National Renewable Energy Laboratory showed that the median life cycle emissions from enhanced geothermal power plants were 32 g CO₂‑eq/kWh, just 6% of the median life cycle emissions from a natural gas power plant, with most of the emissions generated during construction rather than operation. Geothermal energy has been used for more than a century, but AGS that use the directional and horizontal drilling and hydraulic fracturing techniques developed by the oil and gas industry to access previously inaccessible underground heat resources are relatively new. To date, several small-scale and experimental AGS projects have successfully produced electricity, and in December 2025, the first commercial plant for electricity and heat production delivered electricity to the grid in Germany. 

Why are we excited?

Advanced geothermal energy systems are a potentially transformative climate solution for several reasons. First, they could massively expand clean energy availability. AGS can be deployed in almost any region with hot subsurface rocks. Experts estimate the Earth’s accessible geothermal resources are staggeringly large, and that tapping just 0.1% of the heat under our feet could meet global energy needs for millennia. If technology improvements continue, advanced geothermal could supply around 15% of the world’s electricity by 2050. Second, unlike solar and wind energy, advanced geothermal power plants produce steady baseload power, dispatchable power, and even energy storage. Currently, coal and gas power plants are commonly used to provide stability and backup power to electricity grids around the world. AGS can provide the same energy benefits, complementing wind and solar energy by providing firm capacity and grid stability services to a renewable-heavy electricity grid, without the harmful climate impacts. Third, AGS plants have a relatively small land footprint and can potentially be sited near demand centers (including repurposing old fossil plant sites), improving energy security for regions with limited solar or wind resources.

Recent technological breakthroughs have improved the prospects for AGS. The application of directional drilling and hydraulic fracturing techniques has produced higher fluid flow rates and extended reservoir life. This has dramatically increased the heat extraction per well, overcoming previous limitations and boosting the energy output and economics of AGS. Industry reports show drilling rates in hot rock have increased by 300–500% in the last few years, slashing upfront costs. A recent U.S. Department of Energy report projects that the cost of next-generation geothermal projects, including AGS, will fall below that of other baseload power sources such as nuclear and natural gas with carbon capture and storage (CCS) by 2035. Other projections suggest that geothermal electricity could drop to around US$50/MWh by the 2030s, competitive with other renewables and nuclear. Finally, AGS leverage a skilled workforce and supply chain from the oil and gas sector. The necessary drilling rigs, subsurface imaging, and engineering expertise already exist, which could help scale up AGS faster than entirely new industries.

Why are we concerned?

Despite its promise, AGS face several challenges that temper its near-term prospects. To bridge the gap from pilot stage to commercialization, the industry needs more demonstration projects, case studies of success, and greater public trust. This is challenging because advanced geothermal projects today have high upfront capital costs, primarily due to deep drilling and, for EGS, hydraulic stimulation expenses, as well as high operational costs. Current AGS electricity is also far more expensive than conventional renewables, often hundreds of dollars per MWh. Until these costs decline, the industry may struggle to attract the investment financing needed to scale up. Moreover, the geological uncertainty in any given project is high because limited geophysical data in many regions makes it hard to pinpoint the best spots to drill. Developers must invest in exploration with no guarantee of finding an adequate resource, so early projects carry a significant risk of cost overruns.

Safety and environmental concerns also pose challenges. In some types of geologies, enhanced geothermal systems, which use hydraulic fracturing to create the heat exchange reservoirs and circulate fluid underground, can trigger small earthquakes. Some EGS have been halted after local earthquakes caused alarm and minor damage. Because they use water and circulate hot brines, AGS could pose risks for groundwater contamination or water consumption in arid regions, although geothermal system designs that use closed-loop systems or non-potable water can avoid these problems. Finally, geothermal projects often face regulatory and logistical hurdles and lengthy permitting processes. In many countries, regulatory regimes and incentives have focused on solar, wind, and even nuclear, while geothermal energy (and especially AGS) has received comparatively little support. This means AGS developers may struggle with financing and grid access due to policy gaps or obstacles. 

What is our assessment?

There is strong evidence that green roofs sequester carbon and may reduce building energy consumption, although emissions reduction data are limited and vary with geography, roof design, and other factors. The potential climate impact of increasing green roofs is likely too small to be globally significant (>0.1 Gt CO₂‑eq/yr ). The solution, however, is considered “Worthwhile” because it can reduce energy use in buildings and sequester carbon while helping communities adapt to climate change and benefiting human health, the environment, and building owners.

What is it?

Vegetation planted on specially engineered rooftops sequesters CO₂ through photosynthesis and provides indirect cooling for buildings through evapotranspiration, reflecting heat back to the atmosphere, and shading. This cooling plus the added insulation inherent in the design can reduce the air conditioning loads of the building, particularly compared to dark rooftop surfaces, and therefore reduce emissions from the electricity used to power cooling systems. Green roofs can also reduce heating energy use and corresponding GHG emissions due to the insulation that soils and plant matter provide. Green roofs are in use in all regions of the globe, but concentrated in high- income countries. 

Does it work?

There is strong evidence that green roofs sequester carbon and can reduce the energy consumption and therefore emissions from cooling and heating buildings. Carbon sequestration by vegetation on green roofs has been documented in several studies. A study in Germany found that plants absorbed 141 g carbon/m2/year (517 g CO₂ /m2/yr) over a 5-year period. However, carbon sequestration rates are difficult to generalize due to variations in design, plant types, and climates. 

Reported building energy savings from green roofs can range from negligible to 60% or more for cooling. For heating the savings can reach 45% or more, but some studies also show roughly a roughly 10% increase in heating energy use with a green roof. The large variability in energy savings outcomes is due to differences in climate; existing insulation and other properties of buildings; green roof design, vegetation and maintenance practices; and measurement and modeling approaches. The highest energy savings potential has been calculated in dry-winter subtropical highlands for cooling and in humid subtropical climates for heating. Areas with short and mild winters are most likely to see heating energy use increase with green roofs, but these areas often have net energy savings when heating and cooling are combined, and most studies of green roofs show a reduction in heating energy use. 

When combined with the carbon sequestration effect of vegetation, green roofs appear to consistently reduce GHG emissions. 

Why are we excited?

Green roofs and other urban green spaces (see Increase Urban Vegetation) provide valuable climate adaptation, human health, environmental, and economic benefits. Green roofs can help cities adapt to climate change because the vegetation reduces heat exposure during extreme heat, while the soil and root systems absorb stormwater, thereby reducing runoff and flooding risks during extreme rainfall. Green roofs improve human health because vegetation filters the air and reduces noise transmission, and interactions with green spaces, including green roofs, have been shown to improve mental well-being. Green roofs can increase biodiversity and habitat and remove water pollution. They also can increase the property value of a building and prolong the longevity of the roof.

Why are we concerned?

Increasing green roofs can be challenging due to high up-front cost, lack of supportive policies, structural and climate limitations, maintenance requirements, and lack of awareness. A green roof can cost three to six times more than a conventional roof, and although it can save energy for cooling and heating, the returns on investment can be lengthy and savings may not be enough to fully offset the higher costs. In addition, not all roofs can support vegetation, rooftop plants can struggle to survive in hot and dry climates, and green roofs may increase heating energy use in buildings in climates with short and mild winters. A green roof also requires maintenance such as watering, plant care, weed control, pruning, and regular inspections. Finally, a lack of awareness is a major barrier to greater adoption. We also noted a lack of measured, rather than modeled emissions reduction data and on current and potential green roof adoption globally.