Currently, fossil fuels (coal, oil and natural gas) provide the majority of the world’s energy supply. Renewable energy sources (like solar, wind, hydro, biomass, and geothermal) make up about 14% of global primary energy supply, and nuclear energy supplies about 5% (IEA 2019). This energy is then utilized by four sectors:
- Industrial sector (which includes agricultural processes, chemicals, iron/steel, mining, construction, forestry, etc.)
- Residential sector (including household heating, cooling, lighting, consumer products, etc.)
- Commercial sector (including commercial heating, cooling, lighting, refrigeration, computers of offices, stores, hospitals, schools, etc.)
- Transportation sector (all road, rail, air, water and pipeline needs)
World Greenhouse Gas Emissions in 2016 (Sector | End Use | Gas)
The energy system has greatly improved the standard of living for many humans, but the accumulation of carbon dioxide and other greenhouse gas emissions from energy production (burning of fossil fuels) are primarily responsible for climate change. If left unaddressed, climate change will result in catastrophic disruptions to all life on Earth, including humans (IPCC 2014). To minimize the impact of the energy system on the climate for the long haul, it will be necessary to provide the energy services in each of these sectors with clean energy sources, all while maintaining and equitably improving quality of life.
Reaching a clean energy system that eliminates greenhouse gas emissions is a challenge that requires support and action from all sectors of society. The global energy system has to go from over 80% fossil energy today with about 33 gigatons of carbon dioxide equivalent (GtCO2e) (IEA 2019) entering the atmosphere each year to zero emissions. The longer it takes for global emissions to peak, the steeper the annual decline has to be from that point if desired temperature goals are to be met.
Energy expert Vaclav Smil notes that past energy transitions take multiple decades (or longer) to achieve. Accelerating the timeline for an energy transition that limits average global warming to below 2ºC / 3.6ºF will take a focused effort and considerable political will—a transformation of the global energy system. Efficiency, consumer choice, advances in technologies, and equitable energy services for underserved populations are all at play. At our current rates of emissions, we’ll exceed the carbon budget for 1.5°C in less than a decade, and the 2°C carbon budget in 20-25 years. Limiting global warming to either a 1.5ºC or 2ºC increase will be incredibly ambitious, but necessary to avoid the catastrophic impacts of climate change on a business-as-usual pathway. While the difference between a 1.5ºC vs. a 2ºC increase sounds small, the change in impacts is significant for natural and human systems. Food production, human health, and various vital ecosystems (notably coral reefs) will be much less impacted and better able to adapt in a 1.5ºC future (IPCC 1.5ºC Special Report 2018).