Climate Change: What Are Net-Zero Emissions?

September 4, 2024

Climate Change: What Are Net-Zero Emissions?

“Net-zero emissions” refers to a situation in which humancaused greenhouse gas (GHG) emissions from sources such

as fossil fuel combustion and deforestation are fully

balanced by carbon dioxide removal (CDR) from the

atmosphere. Methods of removal include natural absorption

and storage in forests and other ecosystems as well as

technological removal and storage.

When emissions of carbon dioxide (CO2) are balanced by

and equal to the removal of CO2, the net addition of CO2 to

the atmosphere is equal to zero. This balance is referred to

as net-zero CO2. CO2 is not the only GHG. Human-caused

emissions of other GHGs—including methane (CH4),

nitrous oxide (N2O), and hydrofluorocarbons (HFCs)—also

increase global temperatures. The influence of GHGs on

global temperatures is the combined effect of CO2 and the

other non-CO2 GHGs. The combined influence of all GHGs

may be determined by normalizing the global warming

potentials of the GHGs to the global warming potential of

carbon dioxide (CO2). This results in a metric of carbon

dioxide equivalent (CO2e) to compare across GHGs.

Net-zero GHG means that the combined net emissions of all

GHGs must be zero, accounting for the different warming

effects of the various GHGs. For example, methane is a 2730 times stronger GHG than CO2, over a 100-year time

horizon.

No commercially available method for removing non-CO2

GHGs from the atmosphere exists. This means that to

balance emissions of non-CO2 GHGs that cannot be abated,

additional removals of CO2, by the use of CDR, would be

needed. These removals are sometimes known as negative

emissions. Net-zero GHG is achieved when CO2e emissions

of all GHGs are equal to CO2e removals from the

atmosphere through removals of CO2.

Application of the Net-Zero Concept

The concept of net-zero emissions has found application in

international and domestic climate change policy. Humancaused CO2 emissions increase the levels of CO2 in the

atmosphere. Higher levels of CO2 result in increases in

global average temperature and a corresponding increase in

global net negative effects. The Intergovernmental Panel on

Climate Change (IPCC) has estimated that human activity

since the Industrial Revolution has resulted in 1.07oC of

warming compared with a preindustrial baseline

temperature. The U.S. Global Change Research Program

(USGCRP) stated, “With every additional degree of

warming, the United States is expected to see increasingly

adverse consequences.” There is broad scientific consensus

that if society does not halt the accumulation of CO2 in the

atmosphere, global warming will continue and the risk of

more severe climate impacts will increase.

Temperature Stabilization and Net-Zero

Global temperatures are generally not expected to stabilize

until after GHG emissions are at net-zero. The sooner netzero is attained, the smaller the temperature rise and climate

impacts are likely to be.

Climate goals for global temperature stabilization have

been set by international agreement under the Paris

Agreement (PA). The PA is the second major subsidiary to

the United Nations Framework Convention on Climate

Change (UNFCCC), which the United States ratified. The

temperature aims of the PA are stated as

[h]olding the increase in the global average

temperature to well below 2°C above pre-industrial

levels and pursuing efforts to limit the temperature

increase to 1.5°C above pre-industrial levels.

Climate scientists use climate models to project the

behavior of the earth’s climate under a range of potential

human-driven emissions scenarios. Using climate models,

researchers have estimated when net-zero GHG would need

to be reached to achieve these PA climate goals. The IPCC

Sixth Assessment Report and the USGCRP Fifth National

Climate Assessment state that achieving net-zero CO2 by

2050 and net-zero GHG later in the 21st century are

consistent with limiting the increase in global temperatures

to 1.5oC above the pre-industrial level. As models, methods,

and emissions scenarios vary, there is a degree of

uncertainty in these estimates.

Carbon Dioxide Removal and Hard-toAbate Emissions

Most climate scientists do not consider the elimination of

all human-caused GHG emissions feasible, in part because

of the difficulty of fully eliminating emissions from the

global economy. For example, in some industries, such as

steel and cement, CO2 emissions are particularly

challenging to abate because they are generated during the

chemical reactions of production.

Some scenarios of the IPCC and the USGCRP combine

projected large reductions in emissions with humanmediated, long-term carbon dioxide removal. CDR methods

include enhanced CO2 removal on land by forests, crops,

and soils; ocean-based removal in coastal areas (i.e., blue

carbon) and the open ocean (e.g., iron fertilization); and

mechanical removal by direct air capture. In the scenarios

described above, GHG emissions are reduced to levels that

can be balanced by human-mediated CDR, such that the net

addition of GHGs to the atmosphere is zero. The scenarios

in these reports estimate that net-zero GHG could be

reached if human-mediated CDR is used to remove process

emissions from industrial sectors that are too difficult, too

expensive, or not currently possible to eliminate.

https://crsreports.congress.gov

Climate Change: What Are Net-Zero Emissions?

Net-Zero in Federal Policy

The net-zero concept appears in both enacted legislation

and executive branch actions. Provisions in recent

legislation funded emissions reductions activities, in some

cases citing achieving net-zero GHG emissions in specific

contexts. Executive orders from the Biden Administration

have established a climate policy goal of reaching net-zero

GHG emissions by 2050 through both emissions reductions

and CDR. While many federal activities support emissions

reductions and CDR, this document focuses on those in

which net-zero is the stated policy.

The Inflation Reduction Act

In 2022, Congress passed P.L. 117-169, commonly known

as the Inflation Reduction Act (IRA), which has two

provisions using net-zero criteria:

• Section 50161. Advanced Industrial Facilities

Deployment Program. This section appropriates

approximately $5.8 billion in financial assistance to

industrial or manufacturing facilities to help them adopt

“advanced industrial technology at an eligible facility.”

One of the criteria for receiving the assistance is the

level of emissions reductions from an industrial or

manufacturing facility. Industrial technologies that

accelerate progress to net-zero through GHG emissions

reductions are supported. The industries eligible for

assistance include the steel, cement, and chemical

industries, as well as other energy-intensive processes.

• Section 70006. FEMA Building Materials Program.

This section authorizes the Administrator of the Federal

Emergency Management Agency (FEMA) to provide

financial incentives for “net-zero energy projects.” A

January 2024 FEMA memorandum describes the

implementation of IRA Section 70006. Financial

assistance must be tied to disaster recovery or

mitigation, and applicants are encouraged to include netzero aspects in such projects. Net-zero energy projects

are to be funded on the same cost-share basis as other

FEMA projects. Funding is available for projects with

buildings that meet the energy performance and

renewable generation standards of the International

Energy Conservation Code for new construction and the

International Green Construction Code for existing

buildings. The combination of energy efficiency and the

use of renewable energy in these standards is considered

compliant with the FEMA specifications for a net-zero

energy project.

Executive Actions

Executive actions on climate of the Biden Administration,

including the Long-Term Strategy of the United States:

Pathways to Net-Zero Greenhouse Gas Emissions by 2050

and some executive orders, have included net-zero GHG as

a policy component.

A key aspiration of the Biden Administration Long-Term

Strategy is to achieve a 50%-52% GHG emission reduction

by 2030 (compared with 2005 levels) and net-zero GHG by

2050. These goals are consistent with the PA to reduce the

risks and impacts of climate change. The Long-Term

Strategy includes scenarios that achieve these goals through

a combination of emissions reductions and CDR. CO2

removal by CDR methods accounts for between 10% and

20% of total net-zero GHG emissions reduction.

Several recent analyses from groups in the private sector,

academia, and the federal government estimated U.S. net

GHG emissions reductions projected through 2030 and

found that these estimated emissions reductions would

likely not reach the 50%-52% reduction goal.

President Biden has issued two executive orders that

include net-zero provisions, listed below:

• Executive Order 14082 of September 12, 2022,

Implementation of the Energy and Infrastructure

Provisions of the Inflation Reduction Act of 2022. The

order’s stated purpose is to “effectively implement” the

IRA. This executive order directs certain federal

agencies to, among other things, prioritize a set of

climate goals for the United States. These climate goals

set out in Section 2 of the order include reducing GHG

emissions 50%–52% below 2005 levels by 2030,

achieving a carbon pollution-free electricity sector by

2035, and achieving net-zero GHG emissions by 2050.

• Executive Order 14057 of December 8, 2021,

Catalyzing Clean Energy Industries and Jobs Through

Federal Sustainability. This executive order states a

policy for the federal government of leading by example

to achieve economy-wide net-zero emissions by 2050,

through the use of its scale and procurement power. The

order directs the federal government to achieve a

portfolio of net-zero energy buildings by 2045 and to

achieve net-zero emissions in federal procurement,

including the use of construction materials with lower

embodied emissions, without specifying a target date.

Considerations for Congress

The 117th Congress passed legislation with emissions

reductions and CDR provisions, including the IRA and the

Infrastructure Investment and Jobs Act (P.L. 117-58). This

legislation provided supplemental appropriations and tax

incentives that support emissions reductions and CDR,

components of achieving net-zero emissions. Recent

analyses have estimated U.S. emissions reductions and

CDR and found that the United States may not be on track

to reach 50%-52% emissions reduction by 2030.

These estimates may play a role in whether Members of

Congress consider enhanced oversight of federal climate

policy and whether to take additional legislative action with

respect to the climate goals.

Jonathan D. Haskett, Analyst in Environmental Policy

https://crsreports.congress.gov

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Climate Change: What Are Net-Zero Emissions?

Disclaimer

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