What are the solutions?

Proliferation of turbines, dropping costs, and heightened performance mean onshore wind farms are at the forefront of initiatives to address global warming.

Solar farms tap the sun's virtually unlimited, clean, and free fuel, using large-scale arrays of hundreds, thousands, or in some cases millions of photovoltaic panels.

Rooftop solar is spreading as its cost falls, driven by incentives to accelerate growth, economies of scale in manufacturing, and advances in photovoltaic technology.

Geothermal power — literally “earth heat” — taps into underground reservoirs of steamy hot water, which can be piped to the surface to drive turbines that produce electricity.

Nuclear power is complex, expensive, and risky, but it has the potential to avoid emissions from fossil fuel electricity. Project Drawdown considers it a "regrets solution."

With competitive costs and investment growing, offshore wind energy is at the crest of initiatives to supply the world with clean power.

Concentrated solar power uses solar radiation as its primary fuel. Arrays of mirrors concentrate incoming rays to heat a fluid, produce steam, and turn turbines.

Wave - and tidal - energy systems harness natural oceanic flows — among the most powerful and constant dynamics on earth — to generate electricity.

Industrial-scale anaerobic digesters control decomposition of organic waste, and thus its methane emissions. They also produce biogas, an energy source, and digestate, a nutrient-rich fertilizer.

Biomass energy is a “bridge” solution for transitioning to 100 percent clean, renewable energy. Using sustainable feedstock — waste biomass or perennial crops — is crucial.

Water heating is a major energy use. Solar water heaters use the sun's radiation and can reduce that energy consumption by 50 to 70 percent.

Placed within a free-flowing river or stream, in-stream turbines capture water's energy without a dam. In remote communities, they can replace expensive, dirty diesel generators.

Power plants produce large amounts of waste heat. Cogeneration systems capture that thermal energy and put it to work — for district heating or additional electricity.

At backyard- and farmyard-scale, anaerobic digesters are used to manage organic waste. They control methane emissions, while producing biogas (an energy source) and digestate (nutrient-rich fertilizer).

Incineration, gasification, and pyrolysis are means of deriving energy from trash. A transitional solution, waste-to-energy can reduce emissions, but has high social and environmental costs.

With capacity of 100 kilowatts or less, micro wind turbines are often used to pump water, charge batteries, and provide electrification in rural locations.

Standalone batteries and electric vehicles make it possible to store energy at home or work. They ensure supply even when variable renewables are not producing.

Energy storage — daily, multiday, and longer-term or seasonal — is vital to reduce emissions from polluting “peaker” plants and accommodate the shift to variable renewables.

For electricity supply to become predominantly or entirely renewable, the grid needs to become more flexible and adaptable than it is today.

A microgrid is a localized grouping of distributed energy sources, like solar and wind, together with energy storage or backup generation and load management tools.