A climate science milestone on Colorado’s Continental Divide

On January 16, 1968, in a bracing chill at 11,568 feet above sea level, a Colorado researcher collected an air sample at Niwot Ridge, on the doorstep of the Indian Peaks mountain range. The sample was carried down the mountain and then measured for carbon dioxide at a lab in Boulder, Colorado. The result: 322.4 parts per million.

NOAA was not officially established until 1970, but this air sample produced the first measurement for NOAA’s Global Greenhouse Gas Reference Network. In the 50 years since, more than 274,000 air samples have been collected at over 60 sites around the globe, including more than 9,000 at Niwot Ridge. All have been transported to what is now NOAA’s Global Monitoring Division labs in Boulder for measurements of carbon cycle gases, like carbon dioxide, methane, carbon monoxide and other gases.

From this inauspicious start, NOAA’s Global Greenhouse Gas Reference Network has evolved into one of the international climate science community’s most valuable resources - a long, uninterrupted and highly accurate accounting of Earth’s changing atmosphere.  

Air samples are collected on a weekly basis from locations spanning the Canadian Arctic to the South Pole - continental sites ranging from deserts to tropical forests to barren ice caps, on small islands, and on ships crossing the oceans, by scientists and technicians, as well as soldiers, ranchers, mariners, school teachers, lighthouse keepers, a monk, and a host of other volunteers. One dedicated group of volunteers in Mongolia sends a hearty soul on a 12-hour overnight train ride once a month to deliver air samples to a shipping destination.  

Over the years measurements were refined and added, and now samples are analyzed for as many as 60 different trace gases, some at a resolution of parts per trillion. Collection and measurement methods have changed over the decades, but extraordinary steps taken to ensure accuracy mean that historical data are valid and continue to be used by researchers around the world to understand the carbon cycle.  

Thanks to that 1968 Niwot Ridge sample, NOAA’s Global Greenhouse Gas Reference Network database is the third-longest continuous carbon dioxide record in the world, behind the Scripps Institution of Oceanography’s Mauna Loa, Hawaii, and Antarctic records. NOAA maintains independent sampling stations at Mauna Loa and the South Pole as well.

On January 15, 2018, almost 50 years to to the day since the first sample was collected, a researcher sampled the air at Niwot Ridge. This time, instruments measured 410.24 ppm of carbon dioxide, an increase of 27 percent over that first sample.

For more information on NOAA's Global Greenhouse Gas Reference Network, contact Theo Stein: theo.stein@noaa.gov.