Human-induced CO2 emissions are the primary driver of rising atmospheric CO2 levels, leading to climate change, with CO2 remaining in the atmosphere for an average of over 400 years.

Atmospheric CO2 and human-induced emissions

Latest data and insights on CO2 levels in Earth's atmosphere, including human-induced (anthropogenic) CO2 emissions, increases, breakdowns, absorption, and carbon sinks.

Atmospheric CO2 levels and human-induced emissions

What is the Monthly Average Atmospheric CO2?

This is the average amount of CO2 that is in the atmosphere in a given month. The monthly average highlights the seasonal variation.

The primary unit here is parts per million (ppm), which describes the concentration of atmospheric CO2 per year. The secondary unit here is gigatonnes, which describes the weight of atmospheric CO2 per year. We show this to be able to relate to emissions, which are commonly expressed in gigatonnes.

We see a seasonal cycle with the lowest values around September. This is mostly due to the fact that the northern hemisphere has a large temperate land mass where plant growth absorbs CO2 from the atmosphere in spring and summer and plant decay releases CO2 in autumn and winter. The southern hemisphere has the opposite seasonal cycle, but it doesn&apos;t have the large land mass to counteract the northern cycle.

Wikipedia: Carbon Dioxide in Earth&apos;s Atmosphere

YouTube: NOAA Carbon Dioxide pumphandle - 2024: History of atmospheric CO2, from 800,000 years ago until January 2024. 

NOAA&apos;s Global Monitoring Laboratory operates a global network of air sampling sites where they measure CO2 and provide data on monthly averages.

Globally averaged marine surface monthly mean data

Monthly Average Atmospheric CO2

What are the Human-Induced Yearly CO2 Emissions?

This refers to the total yearly CO2 emitted through human activities, such as the combustion of fossil fuels, expressed in gigatonnes. In the scientific literature, it is referred to as anthropogenic emissions. Anthropogenic CO2 emissions are critical because they are the main driver of the increasing atmospheric CO2 that is warming the Earth. Human-induced CO2 emissions also cause an increase in CO2 absorption by the ocean, which leads to ocean acidification.

There is an important distinction between net and gross emissions that we must bear in mind. Gross emissions are the total sum of emissions from human activity that emit CO2 into the atmosphere. Net emissions take the absorption by human activities into account to highlight the net effect of human activities.

Global Carbon Project: Global Carbon Budget Presentation

CO2 emissions are expressed in the total weight in gigatonnes per year.

Up until the 1940s, a long period of a slow and steady rise in CO2 emissions was driven by coal combustion and land-use changes, such as deforestation. There was a temporary decrease of emissions during the two world wars and the Great Depression. After the Second World War there was a strong rise in oil use, which led to a 20-year period of increasing emissions. Through the 70s, 80s and 90s, emissions still increased every year, but more slowly, with some years of decrease around the two oil crises and the dissolution of the Soviet Union.

The significant peak in 1997 is from Indonesian forest fires due to changes in land use.

In the early 2000s, rapid development in China caused a major increase in emissions from coal combustion. The USA and Europe, which have historically emitted the most CO2 emissions, have seen a decrease in emissions since roughly 2008, mostly from reduced coal combustion.

The Global Carbon Project data for human emissions is the sum of fossil CO2 emissions plus land-use change emissions. The fossil data is based on four main datasets containing global and national CO2 emissions. The uncertainty in global fossil CO2 emissions is estimated at ±5%. The land use change emissions are based on three bookkeeping models; these models also estimate the land-use change absorption. There are large uncertainties in the land-use values before 1960.

The values for 2024 are projections by the Global Carbon Project. The 2024 land-use projection is only given for changes in net land-use emissions. The Global Carbon Project did not project changes in reforestation and the human-induced absorption in 2024 is projected to equal that of 2023. The 2024 projection for the atmosphere is updated based on the monthly values from NOAA, which are in the Yearly CO2 Atmospheric Increase chart.

Yearly CO2 Atmospheric Increase

Human-Induced Yearly CO2 Emissions

What is the Yearly Absorption of Human-Induced CO2 Emissions?

This is the yearly total amount of anthropogenic CO2 emissions absorbed by the atmosphere, land, oceans and human activities expressed in gigatonnes. All human-made CO2 emissions initially go into the atmosphere. CO2 is then absorbed from the atmosphere partially and indirectly by land, ocean and human activities. This chart shows the yearly distribution of where the anthropogenically emitted CO2 ends up. Before human civilization started emitting a lot of CO2 there was a natural balance between carbon dioxide in the atmosphere and carbon on land and in the ocean.

It is critical to understand where the human-made emissions are absorbed because of the different consequences.

The absorption of CO2 by the atmosphere is the amount by which atmospheric CO2 increases, and it is in fact the same thing as the Yearly Atmospheric CO2 Increase you can see in the first chart. It is the main driver of global warming.

Absorption of CO2 on land mainly happens through vegetation growth. We only consider natural processes in this group. This is also known as the land sink.

The oceans dissolve atmospheric CO2 in a process that is also known as the ocean sink. Ocean absorption results in ocean acidification and impacts life in the seas and oceans.

Certain human activities absorb CO2. Absorption by human activities largely goes into human-managed plant growth and cement carbonation. The absorptions are responsible for the difference between net and gross human emissions.

Wikipedia: Land use, land-use change, and forestry

CO2 absorption is expressed in the total weight in gigatonnes per year.

The absorption by land is growing because of increased plant growth in the northern hemisphere due to rising atmospheric CO2 levels and lengthened growing seasons. This chart has high fluctuations because plant growth depends on many irregular factors.

In the last 150 years, there were some years, like 1861 and 1862, where the land emitted more CO2 into the atmosphere than it absorbed. Hence, those values are negative.

IPCC: Annual Report 6, Chapter 5.2.1.4: Land CO2 Fluxes: Historical and Contemporary Variability and Trends

The absorption of atmospheric CO2 by the ocean is steadily increasing as this is dependent on the level of CO2 in the atmosphere. Unfortunately, this causes ocean acidification and introduces many underlying problems.

The steadily increasing human absorption is small compared to human emissions. At the moment, human absorption comes from two underlying processes, namely land-use change and cement carbonation, and both have related emissions that are higher than their respective absorption. Absorption technologies may become important technologies to make human absorption equal human emissions and ensure a net-zero human impact. Technologies like carbon capture at fossil power stations reduce the emissions before they are emitted and are therefore not part of these absorptions.

The Global Carbon Project shares data on atmospheric CO2, the ocean sink, the land sink and human absorption by land-use change and cement carbonation. The atmospheric CO2 data is taken directly from the source, NOAA, to include latest updates and is taken from CO2 measurement stations across the world. The ocean and land sink values are based on combinations of many ocean and vegetation models. Land-use change absorption values come from three bookkeeping models that also estimate land-use change emissions. There are large uncertainties in the land-use values before 1960.

The values for 2024 are projections by the Global Carbon Project. The 2024 land-use projection is only given for changes in net land-use emissions. The Global Carbon Project did not project changes in reforestation and the human-induced absorption in 2024 is projected to equal that of 2023. The 2024 projection for the atmosphere is updated based on the monthly values from NOAA, which are also seen in the Yearly CO2 Atmospheric Increase chart.

Yearly Atmospheric CO2 Increase

Globally averaged marine surface annual mean rates data

Globally averaged marine surface annual mean growth rates data

Yearly Absorption of Human-Induced Gross CO2 Emissions

What is the Breakdown of Yearly Human-Induced Gross CO2 Emissions?

This is a breakdown by source of the yearly CO2 emissions from human activities and processes expressed in gigatonnes. It is critical to know and track the sources of human CO2 emissions in order to understand their individual impacts on climate change.

The sources of human CO2 emissions are

Fossil fuel CO2 emissions from the combustion of coal, oil and gas are emitted by processes in electricity generation, transport, industry, and the building sector. All processes can be linked to human activities. Examples include driving cars with combustion engines burning diesel or gas, or electric cars charged by electricity from a power plant that burns coal.

Fossil CO2 emissions from other processes include sources like cement manufacturing and production of chemicals and fertilizers. Cement also has an absorption factor highlighted in the absorption breakdown chart.

Human civilization emits CO2 by changing and managing its land. Those emissions come, for example, from deforestation, logging, forest degradation, harvest activities and shifting agriculture cultivation. Land-use change also absorbs considerable amounts of CO2, which is shown in the absorption breakdown chart. Land-use change emits more than it absorbs, so the net effect is still emissions, but less than for coal, oil and gas.

Yearly Absorption of Human-Induced Gross CO2 Emissions

Earth System Science Data: GCP 2020 paper: Section 2.2 Land-use change; Section 2.1 Fossil fuel emissions

IPCC: Annual Report 6, 5.2.1.1 Anthropogenic CO2 emissions

CO2 emissions are expressed in the total weight in gigatonnes.

Until the early 1900s, coal was the foremost fossil fuel, contributing to a steady rise in CO2 emissions. From 1910 to 1950, the use of coal didn’t really increase, with declines during the two world wars and the Great Depression. After 1950, coal use grew steadily once more until the 2000-2011 period, when the rapid development of China caused a major increase in CO2 emissions from coal combustion. The USA and Europe started reducing coal combustion around 2008. In the last ten years there has been no overall increase in coal use, but CO2 emissions from coal combustion are still very high.

After the Second World War came a quick growth in oil use that ended with the Arab oil embargo (1973) and the Iranian revolution (1979). Since then, the use of oil – and CO2 emissions from oil combustion – have grown steadily and are still very high.

Emissions from gas combustion have always been lower than those of coal and oil. They have been growing steadily since the 1960s and are still growing fast. Worldwide gas combustion produces almost the same amount of energy as oil and coal, but it emits less CO2, which is why many countries focus on first reducing coal and oil by switching to gas. Despite the lower emissions compared to other fossil fuels, gas combustion is still a major driver of climate change.

Land-use change emissions are high and relatively steady. This chart shows the gross CO2 emissions due to anthropogenic land-use. Land-use change also absorbs significant amounts of CO2 from the atmosphere. The net effect is around 3 gigatonnes and is in a reducing trend. The significant peak of land CO2 emissions in 1997 is from Indonesian forest fires due to changes in land use.

The Global Carbon Project data for human emissions is the sum of the fossil CO2 emissions plus land-use change emissions. The values for 2024 are projections by the Global Carbon Project. The 2024 land-use projection is only given for changes in net land-use emissions, based on only changes processes that emit.

The fossil data is based on four main datasets containing global and national CO2 emissions. They estimate an uncertainty in global fossil CO2 emissions of ±5%.

Land-use change emissions are based on three bookkeeping models, and these models also estimate the land-use change absorption. There are large uncertainties in the land-use values before 1960.

Breakdown of Yearly Human-Induced Gross CO2 Emissions

What is the Breakdown of Yearly Human-Induced CO2 Absorption?

This is a breakdown by human activities and processes of the yearly CO2 absorption expressed in gigatonnes. It is critical to know and track the sources of human CO2 absorption in order to understand how they can reduce human net emissions.

The human activities and processes that absorb CO2 are

Absorption from land-use change is from the changes we make to the land and how we manage land. Absorption comes, for example, from afforestation and other regrowth. Land-use change also emits considerable amounts of CO2, as shown in the emissions breakdown chart. Land-use change emits more than it absorbs, so the net effect is still emissions, although less than from coal, oil and gas.

When cement is created, it starts to absorb CO2 from the atmosphere, and this process is called cement carbonation. However, the process of creating cement also emits CO2, about twice as much as the created cement will absorb. These emissions are included in the Other Fossil group of the Breakdown of Human-Induced CO2 Emissions chart.

Technologies like carbon capture at fossil power stations reduce the emissions before they are emitted and therefore are not part of these absorptions.

CO2 absorption is expressed in the total weight in gigatonnes.

Land-use change absorption is by far the largest absorber and is in a growing trend. The land-use change emissions are larger but relatively steady. This means that the net effect of land-use change is currently at roughly 3 gigatonnes and in a reducing trend.

Cement carbonation is growing. The absorption of CO2 by cement encompasses roughly half of the emissions that were released when the cement was created. This means that, at the moment, creating more cement structures is not a solution to the rising CO2 levels.

The Global Carbon Project has human absorption data on land-use change and cement carbonation. Cement carbonation is an average of two estimates. Land-use change absorption values come from three bookkeeping models. There are large uncertainties in the land-use values before 1960. The values for 2024 are projections by the Global Carbon Project. The Global Carbon Project did not project changes in reforestation and the human-induced absorption in 2024 is projected to equal that of 2023.

Breakdown of Yearly Human-Induced CO2 Absorption

What is the Yearly Atmospheric CO2 Increase?

This is the difference in the atmospheric CO2 of a given year compared to the previous year. We call this an ‘increase’ rather than a ‘change’ because in recent history, every year has had more CO2 in the atmosphere than the previous year. However, in the past there was sometimes a decrease, for example in the 1850s, which is why those values are negative. The yearly CO2 increase depends on the processes that emit CO2 into the atmosphere and absorb CO2 out of the atmosphere. The average lifetime of CO2 in the atmosphere is just over 400 years.

The Yearly Atmospheric CO2 Increase is critical because as long as it increases, the warming effect due to CO2 is also increasing.

The primary unit here is parts per million (ppm), which describes the increase in the concentration of atmospheric CO2 per year. The secondary unit here is gigatonnes, which describes the weight of the increase in atmospheric CO2 per year. We show this to be able to relate to emissions, which are commonly expressed in gigatonnes.

Not only is atmospheric CO2 increasing every year, the rate is also growing. There are large yearly fluctuations that are mostly due to the changes in CO2 absorbed by the Earth’s land mass. You can read about in the Yearly Absorption of Human-Induced CO2 Emissions.

Yearly Absorption of Human-Induced CO2 Emissions

In the chart you can see a smooth line before the late 1950s and a fluctuating line thereafter. In reality, there were fluctuations before the 1950s too, but there are not enough measurements to confidently calculate the yearly fluctuations and that is why there is a smooth line highlighting the trend. In 1958 the direct continuous measurements of atmospheric CO2 started at Mauna Loa under Charles Keeling, after whom the Keeling Curve is named.

The data since 1958 is from NOAA’s Global Monitoring Laboratory, which has a global network of air sampling sites to measure CO2. The atmospheric CO2 increase is calculated by taking the difference between consecutive deseasonalized December-January averages. For the current year we calculate the difference between the latest 12 months of available data and the 12 months before. If monthly data is not yet available, the daily estimate data is used to compare the available days with the same days of the previous year.

The values from 1850 to 1959 are taken from the Global Carbon Budget 2024.

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What is the Yearly Average Atmospheric CO2?

This is the average amount of CO2 that is in the atmosphere in a given year. The yearly average highlights the long-term trends of atmospheric CO2 and allows us to see modern day levels compared to pre-industrial levels, even as far back as the last 800,000 years. This is critical because the amount of CO2 in the atmosphere is directly related to the warming of the Earth. The warming impact due to atmospheric CO2 can be seen in the Monthly Greenhouse Gases Impact on Energy Balance.

Monthly Greenhouse Gases Impact on Energy Balance

In 60 years the CO2 concentration has steadily risen from just over 300 ppm to more than 400 ppm. To get a feeling for the natural concentrations of CO2, we can compare this to historical values.

When we look at the last 1,000 years, we can clearly see that the CO2 level started rising at the end of the 18th century, coinciding with the industrial revolution.

Throughout the last glacial period, roughly 100,000 to 12,000 years ago, we can see a drastic variation in CO2 levels. This 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. However, the changes in CO2 levels were smaller and much slower compared to what we have been experiencing over the last 200 years.

The last 800,000 years offer some perspective on the CO2 levels during the recurring glacial periods and the unusually high CO2 level of our time. The current level of over 400 ppm was unheard of in the past, which saw values between 180 ppm and 300 ppm.

The data are from the Global Carbon Budget 2023 and 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 has a global network of air sampling sites where they measure CO2. They have an annual mean dataset starting in 1980. For the years between 1959 and today that are unavailable, the atmospheric increase values are used to calculate an estimate for the annual means.

The Global Carbon Budget 2024 provides yearly atmospheric increase values going back to 1750, which are used to estimate the yearly atmospheric CO2 between 1750 and 1959.

National Centers for Environmental Information holds datasets that contain reconstructions of historic CO2 levels going back 800,000 years based on Antarctic ice cores.

Antarctic Ice Core Revised Composite and Individual Core CO2 Data

Atmospheric CO₂ and human-induced emissions

Yearly Atmospheric CO₂ Increase

Yearly Average Atmospheric CO₂

Monthly Average Atmospheric CO₂

Human-Induced Yearly CO₂ Emissions

Yearly Absorption of Human-Induced Gross CO₂ Emissions

Breakdown of Yearly Human-Induced Gross CO₂ Emissions

Breakdown of Yearly Human-Induced CO₂ Absorption