U.S. cuts emissions, but global CO2 hits record level

By EPN Staff

Atmospheric carbon dioxide concentrations measured at the Mauna Loa Observatory in Hawaii reached a new record: a monthly average above 430 parts per million.

This is the highest level recorded since systematic measurements began in 1958 and reflects the continued global rise in greenhouse gas accumulation, even as U.S. carbon emissions have declined for years.

Why it matters

The milestone of 430 ppm marks a continued increase in global atmospheric CO2, up from approximately 426 ppm in May 2024.

According to NOAA and the Scripps Institution of Oceanography, this rise reflects ongoing emissions from human activities worldwide, including fossil fuel combustion and land-use changes.

While U.S. emissions have declined over the past decade – due in part to shifts in the power sector, energy efficiency improvements and state and federal climate policies – total global CO2 emissions have continued to increase.

Recent data from the Global Carbon Project shows that emissions from countries such as China and India have grown in line with industrial development and energy demand.

Emissions from China and India are largely driven by coal-fired power generation, expanding manufacturing sectors, and growing transportation demand.

China remains the world’s largest emitter, accounting for nearly one-third of annual global CO2 emissions. India’s emissions continue to rise with its rapidly expanding energy use and economic development.

Both China and India have set long-term climate targets, but their near-term emissions trajectories remain upward.

The bigger picture

For state-level policymakers in the U.S., the latest CO2 data presents a dual challenge: the persistence of global emissions growth and the limited influence any single jurisdiction may have on global atmospheric concentrations.

While many U.S. states have adopted carbon reduction targets, clean energy mandates, and vehicle emissions rules, their cumulative effect represents only a portion of global emissions trends.

The International Energy Agency reports that rising carbon dioxide emissions are primarily being driven by developing and emerging economies, as emissions in regions like North America and Europe have gradually decreased.

The data raise questions about the impacts of state-based climate and emissions-related policies in a global context. These efforts are being overwhelmed by developing countries’ emissions growth.

More details

Measurements at Mauna Loa are used as a global benchmark because of the station’s consistent methodology and relatively isolated location. Monthly averages typically peak in May before declining during the Northern Hemisphere’s growing season.

Scientists note that CO2 remains in the atmosphere for hundreds of years, meaning that today’s levels are shaped by cumulative historical emissions.

As global climate negotiations continue under the UN Framework Convention on Climate Change, the data from Mauna Loa serves as a quantitative indicator of progress – or lack thereof – toward global climate stabilization goals.