Population growth, intensified agricultural practices, increases in land use and deforestation, industrialization and associated energy use from fossil fuel sources have all contributed to increases in concentrations of greenhouse gases in the atmosphere since the industrial era, beginning in 1750.

Since 1990, there has been a 40% increase in total radiative forcing—the warming effect on the climate—by all long-lived greenhouse gases, and a 2.5% increase from 2015 to 2016 alone, according to figures from the US National Oceanic and Atmospheric Administration quoted in the bulletin.

The WMO Greenhouse Gas Bulletin reports on atmospheric concentrations of greenhouse gases. Emissions represent what goes into the atmosphere. Concentrations represent what remains in the atmosphere after the complex system of interactions between the atmosphere, biosphere, cryosphere and the oceans. About a quarter of the total emissions is taken up by the oceans and another quarter by the biosphere, reducing in this way the amount of CO₂ in the atmosphere.

A separate Emissions Gap Report by UN Environment, to be released today, tracks the policy commitments made by countries to reduce greenhouse gas emissions and analyses how these policies will translate into emissions reductions through 2030, clearly outlining the emissions gap and what it would take to bridge it.

Together, the Greenhouse Gas Bulletin and Emissions Gap Report will provide a base for decision-making at the UN climate change negotiations, which will be held from 7-17 November in Bonn, Germany.

WMO, UN Environment and other partners are working towards an Integrated Global Greenhouse Gas Information System to provide information that can help nations to track the progress toward implementation of their national emission pledges, improve national emission reporting and inform additional mitigation actions. This system builds on the long-term experience of WMO in greenhouse gas instrumental measurements and atmospheric modelling.

WMO is also striving to improve weather and climate services for the renewable energy sector and to support the Green Economy and sustainable development. To optimize the use of solar, wind and hydropower production, new types of weather, climate and hydrological services are needed.

Key findings of the Greenhouse Gas Bulletin:

Carbon dioxide CO₂ is the most important anthropogenic long-lived greenhouse gas. Globally averaged concentrations for CO₂ reached 403.3 parts per million in 2016, up from 400.00 ppm in 2015. This record annual increase of 3.3 ppm was partly due to the strong 2015/2016 El Niño, which triggered droughts in tropical regions and reduced the capacity of “sinks” such as forests, vegetation and the oceans to absorb CO2. Concentrations of CO₂ are now 145% of pre-industrial (before 1750) levels.

The rate of increase of atmospheric CO₂ over the past 70 years is nearly 100 times larger than that at the end of the last ice age. As far as direct and proxy observations can tell, such abrupt changes in the atmospheric levels of CO₂ have never before been seen.

Geological records show that the current levels of CO₂ correspond to an “equilibrium” climate last observed in the mid-Pliocene (3–5 million years ago), a climate that was 2–3 °C warmer, where the Greenland and West Antarctic ice sheets melted and even some of the East Antarctic ice was lost, leading to sea levels that were 10–20 m higher than those today.

Methane. Methane (CH₄) is the second-most important long-lived greenhouse gas and contributes about 17% of radiative forcing. Approximately 40% of methane is emitted into the atmosphere by natural sources (e.g., wetlands and termites), and about 60% comes from human activities like cattle breeding, rice agriculture, fossil fuel exploitation, landfills and biomass burning.

Atmospheric methane reached a new high of about 1,853 parts per billion (ppb) in 2016 and is now 257% of the pre-industrial level.

Nitrous Oxide. Nitrous oxide (N₂O) is emitted into the atmosphere from both natural (about 60%) and anthropogenic sources (approximately 40%), including oceans, soil, biomass burning, fertilizer use, and various industrial processes.

Its atmospheric concentration in 2016 was 328.9 parts per billion. This is 122% of pre-industrial levels. It also plays an important role in the destruction of the stratospheric ozone layer which protects us from the harmful ultraviolet rays of the sun. It accounts for about 6% of radiative forcing by long-lived greenhouse gases.

The annual bulletin is based on observations from the WMO Global Atmosphere Watch Program, which coordinates systematic observations and analysis of greenhouse gases and other trace species. Fifty one countries contributed data for the Greenhouse Gas Bulletin. Measurement data are reported by participating countries and archived and distributed by the World Data Centre for Greenhouse Gases (WDCGG) at the Japan Meteorological Agency.