6.3 Sustainability and the Present Energy Picture

Current energy portfolios

Historically, of course, renewable fuels – wood, animal dung, animal fat, and plant oils – were the only fuels available. Fossil fuels didn’t really take off until the 20th century, with coal coming on at the beginning of the century, oil after World War II, and natural gas mostly in the last quarter of the century. However, with their high energy density, fossil fuels have dominated ever since, producing electricity and powering transportation (Fig 1). In 2023, renewables made up only about 14% of global primary energy consumptions.

Figure 1. Global primary energy consumption by source, 1800-2023. OurWorldinData CC BY.

Primary energy is energy that is produced from raw fuel stocks or generated from natural energy sources. This is in contrast to secondary energy that is generated from primary sources, stored, and used – for example, electricity that is produced from natural gas or solar energy, stored in batteries, and then used to power electric cars.

In this data set, traditional biomass comprises wood, charcoal, animal dung, and crop residues.

The US, China, and India lead energy consumption worldwide (Fig 2). Several large economies – Japan, and several European nations, for example – use less primary energy. Overall, the global North dominates energy consumption. In the coming years, US energy consumption is anticipated to increase, with electricity demands expected to as a result of growth in AI, increase in production of hydrogen fuels, electrification generally and in the transportation sector, and increase in in-country manufacturing. Between 2000 and 2006, industrial and commercial energy use is forecast to rise 2.1 and 2.7%, respectively.^[1] Data center electricity needs are anticipated to increase 13-27% between 2023 and 2028.^[2] However, the world energy forecast shows a global decline in energy demand, as increases in energy efficiency continue to take effect.^[3]

Figure 2. Energy consumption by nation, 2023. OurWorldinData. CC BY.

US energy consumption 

Presently, most of the energy used in the US is generated by petroleum (primarily liquid fuels – transportation and industry) and natural gas (primarily energy generation), with coal, nuclear energy and renewables each providing about 9% (Fig 3). Among renewables, biomass provides the majority of energy, mostly from biofuels (primarily corn ethanol) and wood (including cord wood, wood waste, and wood pellets).

Figure 3. US primary energy consumption by energy source, 2023. US Energy Information Administration. Public domain.

One quadrillion BTUs (a common US energy unit) is approximately 293 terrawatt-hours (a common international energy unit).

Current GHG emissions

As of 2023, world CO₂ emissions continue to increase, led by China and the US. Nations are not meeting their pledges to reduce emissions, made under the UN Framework Convention on Climate Change’s Paris agreement. Even if they were to meet pledges, the pledges, so far, do not reach to zero emissions.

Figure 4. Annual CO₂ emissions by world region from 1750-2023. OurWorldinData.org CCBY.

Note that emissions here are direct emissions from burning of fossil fuels and industry. Emissions resulting from deforestation and other land use change are not included.

Current warming trend

As we saw in the first chapter, the planetary boundaries of CO₂ concentration and radiative forcing (the total increase in atmospheric heat retention) – the planetary boundaries associated with global warming – have been crossed, and the planet is no longer in a safe operating space with respective to temperature. The 2023 and 2024 planetary temperatures, boosted somewhat due to the El Niño cycle, but still unexpectedly high, increase the slope of the temperature data (Fig 5). If that trend continues, the planet is on track to warm beyond 1.5°C beyond pre-industrial temperatures within the 2030s. Most recent climate agreements are designed to limit the likelihood of crossing the 1.5°C threshold, or to limit time spent above that threshold. But as we have seen, nations have not delivered on their promises, which were, in any event, insufficient to limit warming to 1.5°C. The average anomaly in 2024 was +1.28°C, according to the US agency NASA.

Figure 5. Global temperatures from 1880 to 2024, with trend line. US NASA. Public Domain.

Knowledge Check

Take a moment to complete the short quiz below to assess your understanding of this section. Read each question carefully and refer back to the content as needed. This quiz is not graded – it’s simply an opportunity for you to reflect on what you’ve learned and reinforce key concepts.