During 2014, human CO2 forcing continued its long march toward ever-more dangerous and climate-damaging levels. By the peak month of May, global CO2 had ranged well above the 400 parts per million threshold, catapulting Earth at raging velocity toward climate and atmospheric states not seen in at least 3 million years.
According to May readings from the Mauna Loa Observatory, the more volatile hourly measures jumped as high as 404 parts per million while daily and weekly averages tended to settle between 401.4 and 402.3 parts per million. Given these trends, overall CO2 levels for May of 2014 are likely to peak at near or just below the astronomical 402 ppm threshold.
(Atmospheric CO2 levels measured by the Mauna Loa Observatory over the past two years. Peak values for 2012 hit near 397 ppm, peak for 2013 hit near 400 ppm, and peak for 2014 is likely to hit near 402 ppm. Image source: The Keeling Curve.)
CO2 levels near 400 parts per million are enough, according to our developed understanding of paleoclimates, to increase global temperatures by between 2 and 3 degrees Celsius, to melt Greenland, West Antarctica and a portion of East Antarctica, and to raise sea levels by 75 feet if sustained over a long term. According to recent glacial research, these very high levels, when combined with additional greenhouse gas forcing and concurrent ocean and atmospheric warming have already been enough to destabilize or push large portions of these major ice systems into irreversible collapse.
(A history of atmospheric carbon dioxide through early this year provided by CIRES and compared to the entire ice core record of the past 800,000 years. Video source: CIRES.)
36 Billion Tons of CO2 Emission per Year and Counting
Measured from peak to peak, the rate of atmospheric increase is likely near 2.5 to 3.0 parts per million per year over the two year period. Averages over the whole range of the past two years show increases on the order of 2.4 parts per million per year — a challenge to recent rates of increase near 2.2 parts per million a year since 2000.
Steadily ramping rates of atmospheric CO2 accumulation are driven by extreme global industrial, agricultural, and land-use emissions. According to the Global Carbon Project, 2013 saw total global CO2 emissions in the range of 36 billion metric tons. This emission was 2.1 percent higher than the 2012 level and about 60 percent higher than the 1990 level at around 22 billion metric tons of CO2. Such an extraordinary pace of emissions puts severe strain on both atmospheric carbon levels and on carbon sinks around the globe. The resulting risk of such a strong continued emission is that global sinks and stores may soon become sources (see methane monster below). An issue of amplifying feedbacks that grows ever more perilous with each passing year.
Rapidly Increasing CO2 Acting in Concert With Ramping Methane, other Greenhouse Gasses
Unfortunately, CO2 is not the only human emission forcing global temperatures rapidly higher. In addition, methane, nitrous oxide, and numerous other greenhouse gasses also make their way into the atmosphere each year through industrial sources. If we combine all these other greenhouse gasses, the total CO2 equivalent carbon emission is now at around 50 billion metric tons each year. A veritable mountain of greenhouse gasses dumped at a pace more than 150 times that of volcanic emissions each and every year.
Overall, the total greenhouse gas forcing from all these sources is now likely in the range of 481 parts per million of CO2 equivalent. This immense heat forcing, were it to remain in the atmosphere long-term, is enough to raise global temperatures by 3-4 C and to melt enough ice to raise sea levels by at least 120 feet. It is also enough, with only two more years of current emissions, to likely lock in an inevitable, irreversible and extraordinarily disruptive increase of 2 C in global temperatures for this century alone.
First Glimpses of the Methane Monster
The most potent and troubling of these additional greenhouse gasses is methane. Over the course of 20 years, methane is about 80 times as powerful a heat trapping gas as CO2 by volume. And though atmospheric methane levels are far less than comparable CO2 levels (at around 1.8 parts per million, or 1/3 the total atmospheric heat forcing of CO2), there is cause for serious concern.
For not only is the industrial emission of methane increasing, primarily through the use of very damaging hydraulic fracturing technologies (fracking), the global emission of methane from the Earth System also appears to be ramping higher. Over recent years, rapidly thawing permafrost and warming oceans both around the world and, particularly, in the Arctic show signs of venting an increasing volume of methane into the atmosphere from terrestrial sources. Though annual official tracking of total Arctic methane emissions at this point is practically non-existent, recent research allows for rational estimation.
Taking into account known emissions from permafrost and the East Siberian Arctic Shelf, and adding in expected emissions from the rest of the thawing Arctic, methane emissions for the entire region are likely around 40 teragrams per year, or about 7% of the global total. This emission is equivalent to that of a major industrial nation and initial indications are that it is growing.
(Atmospheric methane increase since 2007 as measured at the Mauna Loa Observatory. Note the more rapid pace of increase from 2013 through the first quarter of 2014. Image source: NOAA/ESRL.)
The result of combined increases in the human methane emission and in the Earth System emission has been enough to continue to push global levels higher with Mauna Loa readings breaching the 1840 part per billion average by early 2014. What is even more troubling is that the Earth System methane store, composed of both permafrost methane and methane hydrate at the bottom of the world ocean system, is immense.
In total, more than 3,000 gigatons of carbon in the form of methane may be at risk to eventually hit the atmosphere as the Earth continues to warm under the current human forcing. A very large store that could easily multiply the current rate of Earth System methane release many times over. One that represents a clear and present danger for a potentially very powerful amplifying heat feedback to an equally extraordinary initial human forcing.