Doyle Rice

USA TODAY

One of the planet's top dipsticks is in trouble.

The "Keeling curve," the most famous measurement of the world's rising levels of carbon dioxide for the past six decades, is in jeopardy from funding shortfalls.

The Keeling curve, run by the Scripps Institution of Oceanography in San Diego, is the longest continuous record of carbon dioxide measurements on the planet. The measurements were begun in 1958 by Scripps climate scientist Charles David Keeling and are taken near the top of Mauna Loa on the Big Island of Hawaii.

Keeling died in 2005, and his son, Ralph, is now the keeper of the "curve." A physicist himself, he says the ongoing measurements at Mauna Loa are on the "cutting edge of discovering what we're doing to the planet."

Carbon dioxide (CO2) is the greenhouse gas responsible for most of the warming attributable to such gases, according to the National Oceanic and Atmospheric Administration's (NOAA) Earth System Research Lab, which also measures carbon dioxide levels at Mauna Loa and other locations.

Increasing amounts of CO2 and other gases caused by the burning of the oil, gas and coal that power our world are enhancing the natural "greenhouse effect," causing the planet to warm to levels that climate scientists say can't be linked to natural forces.

Carbon dioxide levels were around 280 "parts per million" (ppm) before the Industrial Revolution, when humans first began releasing large amounts into the atmosphere by burning fossil fuels. They're now near 400 ppm.

"The programs have been supported over the years almost entirely through a bundle of federal grants, typically each lasting three years or so, with several grants running at one time," Keeling said on the Scripps blog. Calling the process "haphazard," he added that the past year was especially difficult because several grants expired.

A recent crowdsourcing appeal has brought in some money, he said, but more will be needed to keep the $1 million per year project going. Increased awareness of the funding issues, brought about by the crowdsourcing request, has spurred new funding opportunities from private sources.

"The situation is still very uncertain, but more hopeful," Keeling said. "Still, we don't know yet how these are going to turn out, and the immediate funding situation is still very urgent."

All of this comes against the backdrop of last week's CO2 rise above 400 ppm at Mauna Loa for the second straight year. (CO2 levels peak in the spring when plants come alive, then decrease when the plants die in the autumn.)

Keeling says that within the next two to three years, the measurement will stay above 400 ppm permanently. "It's just a matter of time before it stays over 400 forever," he said. Consistent levels above 400 ppm haven't been seen in human history and perhaps as long as millions of years.

"We are living in extraordinary times," Keeling said.