CO2 Hits Record 431 ppm as NOAA Faces Funding Cuts That Threaten Mauna Loa Monitoring

**TL;DR Atmospheric CO2 reached a record 431 parts per million last month, according to NOAA’s Mauna Loa Observatory. Meanwhile, a 2027 budget proposal would cut funding for the same monitoring network, and U.S. emissions rose again in 2025 after a brief dip, driven partly by data center energy use.

Context The Mauna Loa Observatory sits at 11,141 feet above sea level on Hawaii’s big island. Its high elevation and remote Pacific location let it sample air that has mixed over thousands of miles, providing a baseline that reflects global greenhouse gas levels rather than local pollution.

Since 1958, scientists have recorded CO2 there continuously, creating the Keeling Curve that shows a steady upward trend. To guard against instrument error, both NOAA’s Global Monitoring Laboratory and the Scripps Institution of Oceanography run independent measurement programs at the site, using separate instruments and sampling methods.

Data are filtered to remove spikes from volcanic activity and daily plant cycles, keeping only hourly values that meet strict background air criteria before computing daily averages.

Scientists integrate Mauna Loa data with the Global Greenhouse Gas Reference Network to produce a worldwide trend. They use bookkeeping models such as BLUE, OSCAR and LUCE to estimate net CO2 from land‑use change and forestry, and tools like CarbonTracker to trace atmospheric signals back to regional sources and sinks.

Key Facts Last month’s average CO2 concentration was about 431 ppm, the highest value in the observational record. Compared with the 1958 starting point of roughly 320 ppm, this represents an increase of about 35 percent. Pre‑industrial levels were near 280 ppm or less.

NOAA data show that the average monthly CO2 amount has risen each year since 2021, with the latest reading continuing that upward trajectory.

The NOAA 2027 fiscal year budget proposal includes reductions for several climate monitoring facilities, explicitly naming Mauna Loa as a site at risk of reduced support.

In the United States, emissions declined slightly in 2023 and 2024 but climbed again in 2025; analysts attribute the rebound in part to growing electricity demand from data centers.

What It Means The Mauna Loa record is a cornerstone for tracking global carbon trends; any interruption could weaken the ability to verify whether atmospheric CO2 continues to rise at the observed rate. Dual measurements by NOAA and Scripps provide some redundancy, but sustained cuts could compromise long‑term consistency and delay detection of shifts in carbon sources or sinks.

Policymakers will need to weigh the cost of maintaining these observations against the value of an uninterrupted climate data stream.

Watch for congressional decisions on the NOAA budget and for changes in data center energy consumption that could influence future U.S. emissions trajectories.