Human-induced N2O emissions are the primary driver of the increase in atmospheric N2O. Its very high global warming potential and long lifespan make N2O a significant contributor to climate change.

Atmospheric N2O and Human-Induced Emissions

Latest crucial data and insights on N2O nitrous oxide emissions, human-induced (anthropogenic) emissions, increase, atmospheric levels, breakdowns and more.

N2O Nitrous Oxide Levels and Emissions

What is the Yearly Atmospheric N2O Increase?

This is the difference in the atmospheric nitrous oxide (N2O) of a given year compared to the previous year. We call this an ‘increase’ because in recent history, most years have had more nitrous oxide in the atmosphere than the previous year; in the case of a negative value, this means there was a decrease.

Nitrous oxide has a large warming effect, with a Global Warming Potential (GWP) that is 273 times greater than CO2. Like CO2, but unlike methane, it stays in the atmosphere for a long time, on average 116 years. Besides its warming potential, nitrous oxide is also important because it depletes the ozone layer, which protects us from the Sun’s ultraviolet rays.

The yearly nitrous oxide increase depends on the processes that emit nitrous oxide into the atmosphere and on the nitrous oxide sinks, which mostly comprise photochemical atmospheric breakdown in the stratosphere.

Wikipedia: Nitrous oxide Atmospheric occurrence

IPCC: AR6, Full Report, Section 5.2.3.1 Atmosphere

The primary unit here is parts per billion (ppb), which describes the increase in the concentration of atmospheric nitrous oxide per year. The secondary unit here is a megatonne, which describes the weight of the increase of atmospheric nitrous oxide per year. We show this to be able to relate to emissions, which are commonly expressed in megatonnes.

In recent decades there has been a consistent increase in atmospheric nitrous oxide driven by human emissions. There are three time periods with significant differences in the magnitude of fluctuations. These differences are due to the underlying sources and are explained in the next section.

IPCC: AR6, Full Report, Section 5.2.3 N2O: Trends, Variability and Budget

The data is from several sources linked to the National Oceanic and Atmospheric Administration (NOAA). National Centers for Environmental Information has data from ice core studies, whereby we average the extrapolated yearly increases of the individual studies. This is used for the time period prior to 1978 and highlights the long-term trend, but it does not show the actual yearly fluctuations.

The Global Monitoring Laboratory provides the annual nitrous oxide mole fraction increase (ppb) from Jan 1 through Dec 31. For the current year, we compare the available months to those a year earlier. Since 1978, N2O measurement programs have increased the number of measurements, but there were high fluctuations in global N2O levels due to uncertainty from measurement equipment, which improved over time. Since the late 1990s, a globally distributed network of air sampling sites has greatly increased confidence in the measurements.

NOAA GML: Trends in Atmospheric Nitrous Oxide

Globally averaged marine surface annual mean growth rates

Globally averaged marine surface monthly mean data

Law Dome Ice Core 2000-Year CO2, CH4, and N2O Data

Yearly Atmospheric N2O Increase

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What is the Yearly Average Atmospheric N2O?

This is the average amount of nitrous oxide (N2O) that is in the atmosphere in a given year. The yearly average highlights the long-term trends and hides the seasonal variation.

The primary unit here is parts per billion (ppb), which describes the average concentration of atmospheric methane per year. The secondary unit here is megatonnes, which describes the average weight of atmospheric nitrous oxide per year. We show this to be able to relate to emissions, which are commonly expressed in megatonnes.

There has been a consistent rise in atmospheric nitrous oxide in the last 50 years, from just under 300 ppb to 337 ppb in 2023. The largest driver of this rise is the human emissions from agricultural processes and fossil fuel burning. To realize how high these concentrations are compared to pre-industrial values, we compare them to long-term historical concentrations from ice core studies.

When we look at the last 1,000 years, we can clearly see that the nitrous oxide concentration started rising at the end of the 18th century, coinciding with the industrial revolution.

The 10,000 years before the industrial revolution had steady atmospheric nitrous oxide levels. The last glacial period, roughly 100,000 to 12,000 ago, had much more drastic variations. It was also a drastic period! Ice sheets reached the northern parts of the US, the UK, Germany and Northeast Siberia. There were sea-level changes up to 120 meters.

The last 800,000 years offer some perspective on the nitrous oxide levels during the recurring glacial periods and the unusually high nitrous oxide level of our time. The current level of over 337 ppb was unheard of in the past, which saw values between 200 ppb and 300 ppb.

Wikipedia: Methane in Earth&apos;s Atmosphere

The data is from two subgroups of NOAA, the Global Monitoring Laboratory for recent data and the National Centers for Environmental Information for paleoclimatology data.

The Global Monitoring Laboratory provides annual and monthly atmospheric nitrous oxide averages. We use the monthly trend data to calculate the average for the current year.

The National Centers for Environmental Information provides atmospheric nitrous oxide levels from several ice core studies.

EPICA Dronning Maud Land, EPICA Dome C - 140KYr N2O Data, 800KYr N2O Data

Yearly Average Atmospheric N2O

What is the Monthly Average Atmospheric N2O?

This is the average amount of nitrous oxide (N2O) that is in the atmosphere in a given month. The monthly average highlights the seasonal variation. The graph shows the last 3 years to highlight the seasonal variation.

The primary unit here is parts per billion (ppb), which describes the average concentration of atmospheric methane per year. The secondary unit here is megatonnes, which describes the average weight of atmospheric methane per year. We show this to be able to relate to emissions, which are commonly expressed in megatonnes.

There is a light global seasonal cycle, with higher growth rates between October and March and less growth between April and September. Seasonal variation occurs both in the natural surface emissions and in the natural breakdown in the stratosphere.

caltech.edu: Seasonal cycle of N2O: Analysis of data

The National Oceanic and Atmospheric Administration (NOAA) Global Monitoring Laboratory provides monthly atmospheric nitrous oxide data.

Monthly Average Atmospheric N2O

What are Human-Induced Yearly N2O Emissions?

These are the total yearly nitrous oxide (N2O) emissions from human activities expressed as weight in megatonnes (Mt). In the scientific literature, they are referred to as anthropogenic N2O emissions. Examples of human emissions include the agricultural use of synthetic fertilizer and manure and fossil fuel emissions as well as other sources, as you can see in the next breakdown chart.

Breakdown of Human-Induced Yearly N2O Emissions

Human-induced emissions are the main driver of the increasing atmospheric nitrous oxide that is warming our planet.

The unit megatonne (Mt) describes the weight of emitted nitrous oxide per year.

There has been a strong increase in human-induced nitrous oxide emissions since the 1940s from less than 2 Mt per year up to 10 Mt per year, mostly due to the increased emissions from agriculture due to synthetic fertilizers and manure management.

All of the human-induced nitrous oxide emissions, currently 10 Mt per year, end up in the atmosphere. The yearly increase of atmospheric nitrous oxide in the atmosphere is currently around 6 Mt per year. The difference, around 4 Mt, is due to natural sinks that remove nitrous oxide from the atmosphere, largely because of photochemical breakdown in the stratosphere (2nd layer of the atmosphere).

IPCC: AR6 Full Report, 5.2.3.2 Anthropogenic N2O emissions

The PRIMAP-hist dataset is a rich dataset that combines several published sources to create a historical emissions time series for nitrous oxide and many other greenhouse gases.

Human-Induced Yearly N2O Emissions

What is the Breakdown of Human-Induced Yearly N2O Emissions?

This is a breakdown by source of the yearly nitrous oxide (N2O) emissions from human activities and processes, expressed as weight in megatonnes (Mt). Human-induced emissions are the main driver of the increasing atmospheric nitrous oxide that is warming our planet. The sources of human nitrous oxide emissions are

Emissions related to agriculture are mainly from the use of synthetic fertilizers and manure management.

Synthetic fertilizer, used for agricultural processes, contains a lot of nitrogen. That nitrogen in the soil reacts and causes considerable N2O emissions. The use of excess fertilizer, meaning more fertilizer than the plants can use to grow, causes even higher relative emissions. Applying the right amount of fertilizer at the right time can reduce N2O emissions. There are many technical solutions to reduce emissions while keeping, or even increasing, agricultural yields.

When manure is left on the field or otherwise managed in dry processes, it emits considerable amounts of nitrous oxide. Manure can be managed by wet processes, which reduces nitrous oxide emissions but increases methane emissions. Some technical solutions focus on modifying the animal feed to reduce nitrogen in the manure, thereby reducing nitrous oxide emissions.

All non-agricultural categories together have much lower emissions than agricultural emissions alone.

N2O emissions related to energy are almost all from the combustion of fossil fuels. For example, the combustion of fossil fuels in power plants, cars, and airplanes not only causes CO2 emissions but also emits nitrous oxide (N2O). Any advances to reducing fossil fuel dependency will thus also reduce nitrous oxide emissions.

Most industry-related emissions are from the chemical industry for producing fertilizer, nylon, and similar products. Technologies are available to reduce emissions in these processes.

Nitrous oxide emissions from waste come from, for example, wastewater treatment and landfills.

N2O emissions from agricultural sources, mostly due to synthetic fertilizer and manure, have by far the largest emissions. These emissions have increased rapidly since the 1940s and are continuing to grow. Emissions in the energy sector from fossil fuel combustion have steadily grown and are now the second-largest contributor to human-induced nitrous oxide emissions, at roughly 10% of total emissions. Historically, there was a period between 1960 and 1990 when emissions from the chemical industry had significant growth, but they have also declined since then.

IPCC: AR6, 5.2.3 N2O Trends, Variability and Budget

Atmospheric N₂O and Human-Induced Emissions

Yearly Atmospheric N₂O Increase

Yearly Average Atmospheric N₂O

Monthly Average Atmospheric N₂O

Human-Induced Yearly N₂O Emissions

Breakdown of Human-Induced Yearly N₂O Emissions