Greenhouse Gases Hit Records in 2025 as South Korea Exceeds Global Averages

Three gases reach new highs, with South Korea above each global average

Global carbon dioxide concentrations reached 426.8 parts per million in 2025, while South Korea recorded 432.7, according to figures presented by the Korea Meteorological Administration (KMA). Methane and nitrous oxide also reached their highest global concentrations on record, extending the buildup of gases that trap heat in the atmosphere.

The World Meteorological Organization's Greenhouse Gas Bulletin No. 22 puts global methane at 1,948 parts per billion and nitrous oxide at 339.1 parts per billion. South Korea's corresponding figures were 2,023 and 340.6, placing all three gases above their global averages.

Carbon dioxide rose more slowly than in the previous year, partly because land ecosystems recovered some capacity to absorb carbon after the strong El Niño of 2023–2024. Yet the increase of 2.8 parts per million remained above the average for 2016–2025. A slower increase still left more heat trapping gas in the air.

The bulletin also draws attention to a less familiar problem for countries expanding electricity networks and hydrogen systems: leaks of sulfur hexafluoride, used in electrical equipment, and hydrogen, which indirectly contributes to warming.

WMO Deputy Secretary-General Ko Barrett described the consequences of the growing atmospheric burden:

Greenhouse gases are trapping an unprecedented amount of heat in the atmosphere, providing energy for more extreme weather and associated risks to our economies and societies.

The measurements connect three practical challenges: cutting emissions, tracking how forests and oceans absorb carbon, and preventing gases used in new energy infrastructure from escaping. South Korea contributes to that monitoring through stations at Anmyeondo, Jeju Gosan and Ulleungdo.

What the record numbers mean

Carbon dioxide in 2025 stood at 153% of its estimated concentration in 1750, before industrialization. Methane reached 267% and nitrous oxide 126%. Expressed as increases above those earlier levels, the changes were 53%, 167% and 26%, respectively.

The estimated concentrations in 1750 were 278.3 parts per million for carbon dioxide, 729.2 parts per billion for methane and 270.1 parts per billion for nitrous oxide. Methane has therefore risen to more than two and a half times its earlier concentration.

Parts per million and parts per billion describe how much of a gas is mixed into the air. A carbon dioxide concentration of 426.8 parts per million means roughly 427 out of every million air molecules are carbon dioxide molecules. Methane and nitrous oxide are measured in smaller units because they are less abundant.

Greenhouse gases allow much of the sun's incoming energy to pass through the atmosphere, then absorb and release some of the heat leaving Earth's surface. As their concentrations increase, more heat stays within the climate system.

The bulletin measures the amount already accumulated in the atmosphere. Annual emissions measure how much human activities and natural processes release during a particular year. Concentrations reflect those releases together with the removal of gases by land, oceans and atmospheric chemistry.

Why a slower carbon dioxide rise still matters

Carbon dioxide increased by 2.8 parts per million in 2025, compared with an average annual increase of 2.62 over 2016–2025. The latest rise was about 7% above that decade average, even after easing from the previous year's unusually large jump.

KMA puts the preceding annual increase at 3.5 parts per million; WMO scientists described it as 3.6 in their briefing. Both figures place the 2025 rise below the previous year's increase.

WMO attributes the slowdown to recovering land carbon sinks and lower emissions from fires following the strong El Niño of 2023–2024. A carbon sink is something that absorbs carbon, such as a forest, soil or the ocean. El Niño is a natural warming of the tropical Pacific that can alter rainfall and temperatures across large regions, affecting vegetation and fire conditions.

WMO senior scientific officer Oksana Tarasova explained why the smaller increase still represented a substantial addition to the atmospheric burden:

However, a 2.8 ppm annual increase is still a substantial addition of carbon to the atmosphere from fossil fuel burning.

Around half of the carbon dioxide emitted each year remains in the atmosphere, while land and oceans absorb the rest. Changes in their ability to take up carbon can therefore change the speed at which concentrations rise, alongside changes in emissions.

The longer comparison is striking. The average annual carbon dioxide increase was about 0.8 parts per million in the 1960s, compared with about 2.6 over the latest decade. The recent pace is more than three times as fast.

South Korea's higher concentrations need a closer comparison

South Korea's 2025 carbon dioxide concentration exceeded the global average by 5.9 parts per million. Methane was higher by 75 parts per billion and nitrous oxide by 1.5 parts per billion. Calculated against the global figures, those gaps were approximately 1.4%, 3.9% and 0.4%.

KMA calculates the national background concentrations as the arithmetic average of measurements at Anmyeondo, Jeju Gosan and Ulleungdo. Background measurements seek to minimize the immediate influence of nearby sources and capture air in which gases are more evenly mixed.

The Korean average covers three monitoring locations, while the global figure represents a worldwide observation network. The measured gaps describe the air sampled by those networks; a national emissions inventory separately estimates releases from activities such as power generation, transport, industry and agriculture.

South Korea's average annual increases over the past decade were 2.7 parts per million for carbon dioxide, 9 parts per billion for methane and 1.2 parts per billion for nitrous oxide. The corresponding global figures were 2.62, 10.2 and 1.08.

That comparison reveals a detail obscured by the higher concentration totals: South Korea's decade average growth was faster for carbon dioxide and nitrous oxide, but slower for methane. Methane concentrations remained higher in Korea even though their average annual increase was smaller.

Methane slows, while nitrous oxide keeps rising

Global methane increased by 6 parts per billion in 2025, down from 8 in 2024 and below its decade average of 10.2. Nitrous oxide rose by 1.1 parts per billion, close to its decade average of 1.08.

Methane's history has included periods of faster growth and near stability. Its concentration rose by about 12 parts per billion annually in the late 1980s, changed little from 1999 to 2006, then began increasing again in 2007. WMO links the renewed rise to tropical wetlands and growing emissions from human activities in northern middle latitudes.

About one third of methane emissions comes from natural sources, including wetlands. Human sources account for the remainder and include cattle, rice farming, landfills and the burning of vegetation. Methane has a shorter atmospheric lifetime than carbon dioxide, but accounts for about 16% of the warming effect from gases that persist for long periods.

Nitrous oxide's principal emissions source is nitrogen fertilizer used in farming. Its steady increase adds another challenge alongside energy emissions: reducing the gases released as food is produced.

A tiny amount of electrical insulation gas has a large effect

Sulfur hexafluoride, known as SF6, reached a global average concentration of 12.24 parts per trillion in 2025. Its annual increase of 0.48 parts per trillion was the largest recorded. Compared with 3.5 parts per trillion in 1995, the concentration had risen by about 249%.

Electricity systems use SF6 as an insulating gas and to suppress electrical arcs in equipment handling high voltages. WMO says its atmospheric concentration has increased steadily over three decades alongside global electrification.

SF6 remains in the atmosphere for more than 1,000 years. Over a period of 100 years, a given mass has about 24,300 times the warming effect of the same mass of carbon dioxide. This comparison, called global warming potential, combines how strongly a gas traps heat with how long its effects persist.

WMO identifies gas already contained in electrical equipment as a potential future climate burden if it escapes. It also points to newer alternatives with global warming potential about 98% lower than SF6.

For electricity networks expanding to serve cleaner energy systems, the practical issue extends beyond how power is generated. Equipment selection, containment and recovery of insulating gases also affect the climate benefit.

Hydrogen affects warming through atmospheric chemistry

Atmospheric hydrogen reached 560 parts per billion in 2024, up from 532 in 2010, an increase of about 5.3%. WMO says the reason for its rise over the past decade is not yet known.

Hydrogen is not itself a greenhouse gas, but it can affect the atmosphere's ability to remove methane. It reacts with hydroxyl radicals, highly reactive molecules that help break down methane. More hydrogen can leave fewer of those molecules available to remove methane, allowing its warming effect to persist longer.

Energy systems increasingly use hydrogen as a way to store and transport energy. Electricity from solar or wind power can produce hydrogen, which can be stored and later used when electricity is needed. Hydrogen serves as an energy carrier in this process.

Leaks during production, storage or transport can partly offset the intended climate gains. The WMO bulletin therefore places hydrogen monitoring alongside SF6 surveillance as countries change their energy systems.

South Korea's monitoring network links local measurements to global records

KMA's greenhouse gas data portal says the agency observes seven greenhouse gases as part of WMO's Global Atmosphere Watch programme. Its data help scientists track concentrations and investigate changes in sources and removal processes.

The portal lists records from Anmyeondo and Jeju Gosan beginning in 1999, and from Ulleungdo–Dokdo beginning in 2014. South Korean station measurements also contribute to WMO's calculation of global average concentrations.

The observation history and forthcoming climate meeting provide a short timeline:

• 1999: Greenhouse gas data records begin at Anmyeondo and Jeju Gosan.
• 2007: Continuous SF6 observations begin at Anmyeondo.
• 2012: KMA begins operating the WMO World Calibration Centre for SF6.
• 2014: The portal's Ulleungdo–Dokdo greenhouse gas record begins.
• 2017: Continuous SF6 observations expand to Jeju Gosan and Ulleungdo.
• November 9–20, 2026: COP31 is scheduled in Antalya, Turkey.

The SF6 centre conducts international comparison exercises, trains observers and assesses whether observations meet measurement requirements. These activities help different countries produce records that can be compared reliably.

KMA's portal says the previous year's data are updated each July and may later change under revised quality control standards. Blank entries indicate missing observations, including those caused by unusual readings, equipment repairs or inspections.

More trapped heat meets a shortfall in emissions cuts

The warming influence of greenhouse gases that persist for long periods increased by 51% between 1990 and 2025, according to the figures presented with the bulletin. Scientists describe this influence as radiative forcing: a change in the balance between energy reaching Earth and energy escaping to space.

The United Nations Environment Programme estimates that fully meeting current national emissions targets would cut global emissions in 2030 by only 5% to 8% compared with 2025. That falls short of the 18% reduction it identifies for a pathway giving a 50% chance of limiting warming around the middle of the century to 1.7°C–1.8°C and returning below 1.5°C by 2100.

The same pathway calls for reductions of 45% by 2035 and 69% by 2040, both against 2025 emissions. These are reductions in annual releases, while the WMO measurements track the gases accumulating in the atmosphere.

Tarasova warned that continued fossil fuel burning and a developing strong El Niño could push concentrations higher in 2026 by affecting land carbon uptake. Countries heading to COP31 therefore face pressure to address both continuing carbon emissions and leaks associated with new energy infrastructure.

KMA Commissioner Lee Mi-seon said the agency would use its observation record to support South Korea's climate response:

We will deepen scientific understanding of greenhouse gas changes both globally and in South Korea, and support the country's carbon neutrality policy,

Key Points

• Global carbon dioxide, methane and nitrous oxide concentrations all reached records in 2025.
• Carbon dioxide reached 426.8 parts per million globally and 432.7 in South Korea.
• The global carbon dioxide increase slowed to 2.8 parts per million but remained above the 2016–2025 average of 2.62.
• South Korea recorded higher concentrations of all three gases, although its decade average methane growth was below the global rate.
• SF6 reached 12.24 parts per trillion, with its largest recorded annual increase.
• Hydrogen can indirectly increase warming by slowing methane removal; the cause of its recent atmospheric rise is unknown.
• South Korea's monitoring stations and SF6 calibration centre contribute to international greenhouse gas surveillance.