The amount of carbon dioxide in Earth's atmosphere has increased sharply in the past 100 years as measured from the ground and from satellites. With a more than 50% increase in CO2 since the start of industrial times in the 18th century, scientific measurements have linked this increase primarily to the burning of coal, oil, and gas. This means CO2 levels are now 150% of the value they were at in 1750, and the trend reflects human additions on top of natural factors.

“The additional burden of CO2 added to the atmosphere by human activities, often referred to as ‘anthropogenic CO2’ leads to the current ‘perturbed’ global carbon cycle.” The IPCC notes that “these perturbations to the natural carbon cycle are the dominant driver of climate change because of their persistent effect on the atmosphere.” It explains that anthropogenic emissions from fossil fuel burning and land-use change have made the net land–atmosphere and ocean–atmosphere fluxes “significantly different from zero,” and that “although the anthropogenic fluxes of CO2 … are just a few percent of the gross natural fluxes, they have resulted in measurable changes in the carbon content of the reservoirs since pre-industrial times.”

NASA explains that over the last century, burning of fossil fuels like coal and oil "has increased the concentration of atmospheric carbon dioxide (CO2)." It notes that "the industrial activities that our modern civilization depends upon have raised atmospheric carbon dioxide levels by nearly 50% since 1750," and states that the IPCC concluded it is "unequivocal that the increase of CO2, methane, and nitrous oxide in the atmosphere over the industrial era is the result of human activities." This identifies human activity since the Industrial Revolution as the driver of a major, historically unusual change in the carbon balance between surface reservoirs and the atmosphere.

Chapter 3 of AR6 WG1 concludes that "It is **unequivocal that human influence has warmed the atmosphere, ocean and land** since pre‑industrial times." It notes that AR5 had already concluded that human influence on the climate system is clear, evident from increasing greenhouse gas concentrations, positive radiative forcing, and observed warming. The chapter synthesizes multiple lines of evidence that anthropogenic emissions of CO2 and other greenhouse gases have altered the energy balance of the Earth system and are the dominant cause of observed climate changes since the mid‑20th century.

The AR6 Synthesis Report states: "**Human activities, principally through emissions of greenhouse gases, have unequivocally caused global warming**, with global surface temperature reaching 1.1°C above 1850–1900 in 2011–2020." It further finds that "Observed increases in well‑mixed GHG concentrations since around 1750 are **unequivocally caused by GHG emissions from human activities**." The report notes that land and ocean sinks have taken up a near‑constant proportion (about 56% per year) of CO2 emissions from human activities over the past six decades, implying that anthropogenic emissions have substantially increased the amount of carbon cycling through the atmosphere. It emphasizes that current atmospheric CO2 levels are unprecedented in at least 800,000 years and that widespread, rapid changes have occurred in the atmosphere, ocean, cryosphere and biosphere as a result of human‑caused climate change.

Human activity causes carbon dioxide and other greenhouse gases to be emitted into the atmosphere. Measurements of carbon-13 and carbon-14 relative to carbon-12 confirm that the increase in CO2 concentration since 1800 originates principally from fossil fuel and land clearing emissions. Excess carbon dioxide emitted by human activity is impacting the natural carbon cycle in the environment that has occurred for millions of years.

The web summary of AR6 WG1 Chapter 3 recalls that the IPCC Second Assessment Report (1995) concluded "the balance of evidence suggests that there is a discernible human influence on global climate." Subsequent assessments strengthened this, and AR6 now states that human influence on the climate system is **unequivocal**, based on robust evidence from observed warming, greenhouse gas increases, and physical understanding. The chapter outlines how human activities have affected all major components of the climate system, including atmospheric composition, the global energy balance, and biogeochemical cycles such as the carbon cycle.

In this “Grand Challenges” paper, we review how the carbon isotopic composition of atmospheric CO2 has changed since the Industrial Revolution due to human activities and their influence on the natural carbon cycle, and we provide new estimates of possible future changes for a range of scenarios. Emissions of CO2 from fossil fuel combustion and land use change reduce the ratio of 13C/12C in atmospheric CO2 (δ13CO2). The onset of the Industrial Revolution initiated extensive fossil fuel burning that introduced carbon previously stored in geological reservoirs into the atmosphere. From 1850 to 2015 atmospheric δ13CO2 decreased by 1.8‰… Atmospheric Δ14CO2 decreased by approximately 20‰ between 1850 and 1950 as a result of fossil fuel emissions after the Industrial Revolution.

NASA explains that before the Industrial Revolution, “the exchange of carbon among the atmosphere, oceans, soil, and living things was roughly in balance.” Human activities—especially “burning fossil fuels, changing land use, and producing cement”—now “add about 30 billion tons of carbon dioxide to the atmosphere each year.” It emphasizes that this is “100–300 times more than volcanoes emit,” and that “as a result of human activities, the concentration of CO2 in the atmosphere has increased by about 50 percent since the 18th century,” significantly altering the natural carbon cycle and Earth’s energy balance.

The IPCC assessment reports that human influence has unequivocally warmed the atmosphere, ocean and land, and that about half of human CO2 emissions are removed by land and ocean sinks while the remainder accumulates in the atmosphere. This indicates a persistent human-driven perturbation of the carbon cycle rather than a closed natural balance.

The IPCC press release for AR6 WG1 states: "The report shows that **emissions of greenhouse gases from human activities are responsible for approximately 1.1°C of warming** since 1850–1900." It adds that "the evidence is clear that **carbon dioxide (CO2) is the main driver of climate change**, even as other greenhouse gases and air pollutants also affect the climate." Co‑Chair Valérie Masson‑Delmotte is quoted: "It has been clear for decades that the Earth’s climate is changing, and **the role of human influence on the climate system is undisputed**." The release notes major advances in attribution science, documenting that human‑caused greenhouse gas emissions are the dominant cause of observed changes in temperature and other climate indicators.

IPCC AR6 WG1 Chapter 5 states that since 1750, “anthropogenic CO2 emissions from fossil fuel combustion and land use, land-use change and forestry (LULUCF) are responsible for the observed increase in atmospheric CO2 concentrations from 278 ppm to 410 ppm in 2019.” It describes this as “a substantial perturbation of the global carbon cycle,” noting that “about 46% of cumulative anthropogenic CO2 emissions between 1850–2019 have remained in the atmosphere, 23% have been taken up by the ocean, and 31% by the land.” The chapter concludes that human activities have “profoundly altered the natural carbon cycle on decadal to centennial time scales.”

Human activities are perturbing the global carbon cycle profoundly. Fossil fuel combustion and land use change are the dominant causes of the observed increase in atmospheric CO2 concentration since the pre-industrial period. These activities have added carbon to the atmosphere at rates unprecedented in at least the last 800,000 years, forcing the climate system and altering the functioning of terrestrial and ocean carbon sinks.

Human beings, like other living organisms, have always influenced their environment. It is only since the beginning of the Industrial Revolution, mid-18th century, that the impact of human activities has begun to extend to a much larger scale, continental or even global. Human activities, in particular those involving the combustion of fossil fuels for industrial or domestic usage, and biomass burning, produce greenhouse gases and aerosols which affect the composition of the atmosphere. It is now recognized that land-use change on the present scale may contribute significantly to changing the local, regional or even global climate and moreover has an important impact on the carbon cycle.

NOAA’s Global Monitoring Laboratory documents that global mean atmospheric CO2 has risen from about 280 parts per million (ppm) in the late 19th century to over 420 ppm in recent years, based on ice-core records and direct atmospheric measurements. The site explains that this rapid increase began with the Industrial Revolution and is linked to human activities, primarily fossil fuel combustion and land-use change. It notes that the current rate and magnitude of CO2 rise are much greater than those associated with natural variations over at least the past several hundred thousand years, indicating a major human-induced shift in the carbon balance.

Summarizing the IPCC Fifth Assessment Report (AR5), the European Commission notes that "It is 'extremely likely' (meaning that there is now at least 95% certainty) that **human activities caused most of the observed increase in surface temperature over the last 60 years**." It highlights that "The concentration of carbon dioxide in the atmosphere has **increased by about 40% since 1750 as a result of human activity, almost entirely due to the burning of fossil fuels and deforestation**." The piece explains that since the 1950s many observed changes are unprecedented over decades to millennia, coinciding with rapid growth in anthropogenic greenhouse gas emissions.

Ice-core records indicate that atmospheric CO2 concentration varied between about 180 and 280 ppm over the last 800,000 years. In contrast, since the Industrial Revolution, atmospheric CO2 has risen sharply from about 280 ppm to more than 390 ppm in 2011 due to fossil fuel combustion and land-use change. This rapid increase is unprecedented in the context of the Holocene and reflects a major perturbation to the global carbon cycle.

Natural processes are always influencing the earth's climate and can explain climate changes prior to the Industrial Revolution in the 1700s. In the last century, however, human activities have released large amounts of carbon dioxide and other greenhouse gases into the atmosphere… These greenhouse gas emissions have increased the greenhouse effect and caused Earth’s surface temperature to rise. In addition, human activities emit more than 100 times as much carbon dioxide as volcanoes each year.

NOAA explains that measurements of carbon isotopes in atmospheric CO2 reveal the source of the added carbon. It notes that the observed decline in the 13C/12C ratio and in radiocarbon (14C) in atmospheric CO2 is consistent with the addition of CO2 from fossil fuels, which are depleted in 13C and contain no 14C. These isotopic fingerprints demonstrate that the recent growth in atmospheric CO2 comes predominantly from fossil carbon introduced by human activity, rather than from natural carbon cycle variations.

Reporting on AR6 WG1, UN News states that the report "highlights that **human influence has warmed the climate at a rate that is unprecedented in at least the last 2,000 years**." It notes that "In 2019, atmospheric CO2 concentrations were **higher than at any time in at least 2 million years**, and concentrations of methane and nitrous oxide were higher than at any time in the last 800,000 years." The article quotes IPCC Co‑Chair Valérie Masson‑Delmotte: "It has been clear for decades that the Earth’s climate is changing, and **the role of human influence on the climate system is undisputed**," underscoring the strong scientific consensus on anthropogenic alteration of the climate and carbon cycle.

The IPCC Special Report on Global Warming of 1.5°C states that **human‑induced warming** reached approximately 1°C (likely 0.8–1.2°C) above pre‑industrial levels in 2017 and has been increasing at about 0.2°C per decade (high confidence). It explains that since 2000, the estimated level of **human‑induced warming has been equal to the level of observed warming**, within uncertainties due to natural factors, indicating that recent warming is dominated by anthropogenic greenhouse gas emissions. The report notes that limiting warming to 1.5°C implies reaching net‑zero CO2 emissions globally around 2050 and deep reductions in other climate forcers, directly linking human‑driven carbon emissions to changes in the climate system.

The Global Carbon Project's annual assessments quantify the **global carbon budget**, including fossil CO2 emissions, land‑use change emissions, and the uptake of CO2 by land and ocean sinks. Recent budgets show that **anthropogenic CO2 emissions** from fossil fuels and industry reached around 37–39 GtCO2 per year in the late 2010s and early 2020s, far exceeding natural geological CO2 fluxes and adding a substantial new source of carbon to the atmosphere‑ocean‑land system. The project documents that about half of these human emissions remain in the atmosphere, with the rest absorbed by land and ocean sinks, demonstrating how human activity has changed the magnitude and partitioning of carbon flows in the global carbon cycle.

The paper states that “the burning of our diminishing fossil fuel reserves is accompanied by large anthropogenic CO2 release, which is outpacing nature's CO2 recycling capability, causing significant environmental harm.” It frames current human emissions as exceeding the capacity of the natural carbon cycle: “the anthropogenic carbon dioxide cycle offers a way of assuring a sustainable future… To supplement the natural carbon cycle, we have proposed and developed a feasible anthropogenic chemical recycling of carbon dioxide.” This characterization explicitly describes human-driven CO2 release as a major perturbation to natural carbon fluxes.

Discussing modern CO2 emissions, this review notes: “Since the Industrial Revolution, ocean pH has decreased by 0.1 units, corresponding to a 26% increase in hydrogen ion concentration, as a result of the uptake of anthropogenic CO2 by the oceans.” It emphasizes that “the current rate of ocean acidification is at least an order of magnitude faster than during the Paleocene–Eocene Thermal Maximum, a major global warming event 56 million years ago.” The article links this rapid change directly to human-driven CO2 inputs, illustrating how anthropogenic emissions are altering a key component of the natural carbon cycle (the ocean carbonate system).

A review in Nature Geoscience on the **global carbon budget** notes that since the Industrial Revolution, **anthropogenic CO2 emissions from fossil fuel burning and land‑use change** have become a dominant flux in the carbon cycle. The paper quantifies how these human‑driven fluxes have increased atmospheric CO2 concentrations and forced additional uptake by the ocean and terrestrial biosphere, altering the natural balance and functioning of the global carbon cycle. It emphasizes that the perturbation caused by human activities is large and rapid compared to typical natural variations in the carbon cycle over recent millennia.

The scientific evidence is clear that since the industrial revolution, the ocean has been absorbing more CO2 than it has been emitting. This demonstrates that natural emissions and absorptions were largely in balance before the industrial revolution. Atmospheric CO2 levels and human CO2 emission significantly increased after industrial revolution. As Figure 2 shows, the recent increase in atmospheric CO2 is unseen in the past 800,000 years and… must be caused by human activity. Many lines of evidence… show that human CO2 emissions are the cause of this increase in atmospheric CO2. After reviewing the evidence, scientists have concluded that human-caused CO2 [is] mainly responsible for the increase in atmospheric CO2 after the industrial revolution.

This scientific overview states that combustion of fossil resources and deforestation “currently represents a short circuit from this slow cycle to the short cycle that largely dominates natural regeneration processes. This leads to a rapid accumulation of CO2 in the atmosphere, causing global warming, and ocean acidification that can disrupt marine life.” It notes that atmospheric CO2 stayed near “280 ppmv for at least the previous thousand years” but has risen rapidly since the industrial era, with the rate of increase “well correlated with emissions from human activities.” The article concludes that “over the past century, it is human activities that control the transformations of our environment,” and that only about 50% of anthropogenic CO2 is reabsorbed by natural feedbacks.

Human activity emits carbon dioxide through fossil fuel burning, cement production and land-use change. Since the Industrial Revolution, these emissions have risen from near zero to tens of billions of tonnes per year, fundamentally altering the amount of carbon moving from geological reservoirs into the atmosphere.

The CLEAN climate literacy materials state that there is "overwhelming evidence that human activities, especially burning fossil fuels, are leading to increased levels of carbon dioxide and other greenhouse gases in the atmosphere." They note that the trend of increasing atmospheric CO2 is "caused by the burning of fossil fuels and massive land cover changes" and that carbon isotopes provide a "smoking gun" fingerprint showing the added CO2 comes from fossil fuels. The resource concludes that "human activities, particularly the combustion of fossil fuels, are altering the climate system," highlighting that human-driven changes have disrupted the previous balance of the carbon cycle.

Humans have exerted an enormous influence on the global carbon cycle, largely through deforestation and fossil fuel burning. Beginning with the onset of the industrial revolution at the end of the last century, humans have been burning increasing quantities of fossil fuels as our primary energy source. As a consequence, the amount of CO2 emitted from this burning has undergone an exponential rise… The magnitude of this flow is currently about 9 Gt C/yr. The other form of human alteration of the global carbon cycle is through forest cutting and burning and the disruption of soils associated with agriculture. This process reduces the size of the land biota reservoir, and the burning adds carbon to the atmosphere… Current estimates place the total addition to the atmosphere from forest burning and soil disruption at around 2–3 Gt C/yr.

Recent data reveals that global CO2 emissions were 182 times higher in 2022 than they were in 1850, around the time the Industrial Revolution was underway. The article uses this historical comparison to show how rapidly human emissions expanded relative to the preindustrial era.

Humans, just like all other living organisms, have impacted the global carbon cycle since the dawn of our species. As the world accelerated in the production and transportation of manufactured goods, the production and consumption of fossil fuels grew. As economic growth continued to increase, so did the production of carbon dioxide through fossil fuel combustion. Changes to fluxes in the carbon cycle that humans are responsible for include: increased contribution of CO2 and other greenhouse gases to the atmosphere through the combustion of fossil fuels and biomass; increased contribution of CO2 to the atmosphere due to land-use changes; increased CO2 dissolving into the ocean through ocean-atmosphere exchange; and increased terrestrial photosynthesis. The first two impacts… have, by far, the largest impact on our planet.

This review article states that "human activities have significantly disrupted this natural cycle, leading to increased atmospheric CO2 levels and contributing to global climate change." It emphasizes that "the advent of industrialization and human activities has significantly altered this balance" through burning of fossil fuels, deforestation, and industrial processes. The paper concludes that "human activities such as fossil fuel combustion, deforestation, and industrial processes have significantly disrupted the carbon cycle, leading to increased atmospheric CO2 levels and contributing to global warming" and that human activities "have significantly disrupted its balance."

This explainer notes that "human activities are placing a strain on Earth’s natural carbon cycle" and that "more carbon is released into the atmosphere than absorbed through natural processes, leading to global warming and climate change." It highlights that human CO2 emissions from burning fossil fuels are about "30 billion tons every year; that’s 100 to 300 times more than the natural amount coming from volcanic activity." The article adds that human activities, including fossil fuel use and land-use changes like deforestation, "have resulted in a dramatic increase in carbon dioxide levels since the Industrial Revolution" and that as these activities continue, "the carbon cycle will be incapable of keeping pace with the amounts of carbon emitted each year."

The world has pumped more than 1,800 GtCO2 into the atmosphere since the industrial revolution began, though almost 45 percent has been produced since 2000. The page also notes that around 70 percent of global warming since 1851 is attributable to CO2 emissions from human activities.

Multiple lines of paleoclimate evidence show that for at least several thousand years before the Industrial Revolution, atmospheric CO2 concentrations were relatively stable around 260–280 ppm, indicating that natural sources and sinks of carbon were approximately in balance on century timescales. Since about 1850, human emissions from fossil fuel combustion and cement production have grown to roughly 9–10 gigatonnes of carbon per year, with additional net emissions of about 1–2 gigatonnes of carbon per year from land-use change. These anthropogenic fluxes are large compared to the net imbalance in the pre-industrial natural carbon cycle and have driven the observed rise in atmospheric CO2.