NASA - A Year in the Life of Earth's CO2

New and troubling carbon threshold passed, researchers say

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Scott Sutherland

Meteorologist/Science Writer

Friday, May 8, 2015, 8:26 AM - Global carbon dioxide concentrations have reached a new "benchmark" of 400 parts per million, a level unprecedented in at least a million years.

"Reaching 400 parts per million as a global average is a significant milestone," Pieter Tans, lead scientist of NOAA’s Global Greenhouse Gas Reference Network, said in a press release this week. "This marks the fact that humans burning fossil fuels have caused global carbon dioxide concentrations to rise more than 120 parts per million since pre-industrial times. Half of that rise has occurred since 1980."

Unprecedented in millions of years

These values aren't just high when compared to recent history, or even human history. The release of tens of billions of metric tons of CO 2 into the atmosphere every year, through the burning of fossil fuels, has increased carbon dioxide levels in the atmosphere to levels the planet hasn't experienced in millions to tens of millions of years.

"Current [atmospheric] CO 2 values are more than 100 ppm higher than at any time in the last one million years, and maybe higher than any time in the last 25 million years," says Dr. Charles Miller, the principal investigator of NASA's Carbon in Arctic Reservoirs Vulnerability Experiment (CARVE) mission.

"These increases in atmospheric CO 2 are causing real, significant changes in the Earth system now, not in some distant future climate, and will continue to be felt for centuries to come," added Miller. "We can study these impacts to better understand the way the Earth will respond to future changes, but unless serious actions are taken immediately, we risk the next threshold being a point of no return in mankind's unintended global-scale geoengineering experiment."

An alarming rate of change

While reaching 400 ppm does not represent any known tipping point, or specific danger level, when it comes to the climate system, it is a definite warning sign that we are on a path that is going to get riskier the further along it we travel.

More important than this value, though, is the fact that the current rate of increase in CO 2 levels is over 100 times higher than it was at the end of the last ice age, and rates like this haven't been seen in millions of years.

"Reaching the 400 ppm mark should be a reminder for us that carbon dioxide levels have been shooting up at an alarming rate in the recent past due to human activity," says Dr. Carmen Boening, a scientist in the Climate Physics Group at NASA's Jet Propulsion Laboratory. "Levels that high have only been reached during the Pliocene era, when temperatures and sea level were higher. However, Earth's climate had never had to deal with such a drastic change as the current increase, which is, therefore, likely to have unexpected implications for our environment."

It was "only a matter of time that we would average 400 parts per million globally," Tans said.

2012: Researchers capture carbon dioxide levels of 400 parts per million (ppm) at their Arctic monitoring sites.

2013: The Keeling Curve, using data from atop Mauna Loa, Hawaii, records a May 9 daily average CO 2 concentration of over 400 ppm - a first since monitoring began there in the 1950s, and the very first weekly concentration in excess of 400 ppm.

2014: Mauna Loa records the very first monthly average CO 2 concentration exceeding 400 ppm, in April. Daily averages top 400 ppm for over three and a half months - from the end of March to the middle of July. This equates to 16 weekly averages above 400 ppm, with May logging the highest monthly average (just shy of 402 ppm) ever, since records began there.

Furthermore, based on ice-core data, this is also the first time those levels have been reached in at least 800,000 years, and other research points to the fact that records would need to stretch back to 15 million years or more before those levels would be seen again.



Credit: Scripps Institution of Oceanography

2015: With the Keeling Curve already showing Mauna Loa CO2 averages that leave 2014 levels far behind - monthly averages since Feb exceeding 400 ppm, April topping last year's maximum by nearly 2 ppm and levels still rising - a new report released by NOAA this week expands the view globally, and the news is not good.

After collecting data from a network of 40 sites around the globe, NOAA scientists found that March 2015 logged the first 400+ ppm global monthly average carbon dioxide concentration.

Credit: NOAA, with notation added by author.

Sources: NOAA | Scripps Institution of Oceanography | NASA