'Another Year. Another Record.': Levels of Key Climate-Heating Gases Hit New Highs in 2018, UN Reveals

In yet another signal to global governments that greater ambition is needed to combat the climate crisis, an annual United Nations report released Monday revealed that levels of long-lived greenhouse gases in the atmosphere reached record highs last year.

“We face a stark choice: set in motion the radical transformations we need now, or face the consequences of a planet radically altered by climate change.”
—Inger Andersen, UNEP

The latest World Meteorological Organization (WMO) Greenhouse Gas Bulletin (pdf) provided figures for globally averaged concentrations of three key climate-heating gases in 2018:

• Carbon dioxide (CO₂), which reached 407.8 parts per million;
• Methane (CH₄), which reached 1869 parts per billion; and
• Nitrous oxide (N₂O), which reached 331.1 parts per billion.

“These values represent, respectively, 147%, 259%, and 123% of pre-industrial (before 1750) levels,” the bulletin noted. In terms of contributions to warming the climate, “carbon dioxide is the single most important anthropogenic GHG in the atmosphere” among all long-lived greenhouse gases, the primary focus of the report.

Both methane and nitrious oxide are emitted by natural sources, but about 60 percent of CH₄ emitted into the atmosphere comes from human activities such as biomass burning, cattle farming, fossil fuel exploitation, landfills, and rice agriculture, according to the bulletin. About 40 percent of N₂O comes from human sources, including fertilizer use and various industrial processes.

From 2017 to 2018, concentrations of all three gases surged by higher amounts than the yearly increases documented over the past decade.

“Since 1990, there has been a 43% increase in total radiative forcing—the warming effect on the climate—by long-lived greenhouse gases,” the WMO said in a statement announcing the new bulletin.

The U.N. agency warned that “this continuing long-term trend means that future generations will be confronted with increasingly severe impacts of climate change, including rising temperatures, more extreme weather, water stress, sea level rise, and disruption to marine and land ecosystems.”

The bulletin was released a week before the next U.N. Climate Change Conference, COP 25, is scheduled to start. Representatives from across the globe will meet at the conference in Madrid to discuss governments’ commitments to tackling the human-caused climate emergency, including obligations under the 2015 Paris accord.

WMO Secretary-General Petteri Taalas, in the agency’s statement, tied the bulletin’s findings to the necessity of bolder climate action on a global scale.