Future climate change can be lessened by taking steps to reduce emissions of CO2 and other greenhouse gases. A sharp reduction in emissions of greenhouse gases to the atmosphere is needed to slow climate change and prevent some of the most severe impacts. For the past few decades, international climate talks have focused on establishing goals to minimize the planet’s warming, with the most recent goals set at limiting future warming to 2°C (3.6°F) above preindustrial levels. The 2015 Paris Agreement set an aspirational target of limiting warming to 1.5°C (2.7°F). Since the planet already has warmed about 1°C (1.8°F), scientists have calculated that, in order to stay within the 2°C target, global human-caused greenhouse gas emissions must be reduced by 40 to 70 percent by 2050 compared to 2010, and to near zero or below by 2100.
Key resources: Limiting the Magnitude of Future Climate Change; Environmental Engineering for the 21st Century: Addressing Grand Challenges; Climate Stabilization Targets: Emissions, Concentrations, and Impacts over Decades to Millennia; Warming World: Impacts by Degree
Emissions can be reduced by using energy more efficiently, switching to fuels that produce less (or no) greenhouse gases, and capturing the emissions before they enter the atmosphere. In general, reducing emissions will require that existing and planned transportation, building, and industrial infrastructure be converted to electricity that is generated with substantially lower carbon intensity. Doing so will have the added co-benefit of reducing the environmental and human health impacts associated with coal, oil, and natural gas extraction and fossil-fuel-generated electricity. There are many sources of energy that produce little or no CO2 emissions, including solar, wind, geothermal, and hydropower. Although low-emissions energy sources exist, there is still a long way to go toward their widespread adoption.
Key resources: The Power of Change: Innovation for Development and Deployment of Increasingly Clean Electric Power Technologies; Environmental Engineering for the 21st Century: Addressing Grand Challenges; Limiting the Magnitude of Future Climate Change
Limiting future climate warming due to human activities will require steps to remove carbon from the atmosphere. If goals for climate and economic growth are to be achieved, negative emissions technologies, which remove CO2 from the atmosphere and sequester it, will be an important part of the portfolio of climate responses. Land-based negative emissions technologies—afforestation/reforestation, changes in forest management, enhanced uptake and storage by agricultural soils, and biomass energy with carbon capture and storage—are ready for large-scale deployment at costs competitive with emissions mitigation strategies. However, these existing options cannot provide the amount of negative emissions needed to meet climate goals without unprecedented changes in land use that could affect food availability and biodiversity. Other negative emissions technologies have high potential capacity but are currently limited by high cost in the case of direct air capture and lack of fundamental understanding in the case of carbon mineralization.