Climate scientists watching atmospheric concentrations of greenhouse gases are warning that levels of methane - the second most-harmful greenhouse gas - are rapidly rising.

The report in the journal Environmental Research Letters notes that atmospheric methane rose by 12.5 parts per billion in 2014 and 9.9 parts per billion in 2015.  That is a significant increase from the early 2000s, when concentrations were rising only at about .5 parts per billion per year.  "Looking at the scenarios for future emissions, methane is starting to approach the most greenhouse gas-intensive scenarios," said Stanford University earth scientist Rob Jackson, who co-wrote the study.  "That’s bad news. We’re going in the wrong direction."

Methane is the main component of natural gas, and can leak from drilling and fracking operations.  It's also a result from fermentation in rice paddies and landfills, and flatulence (come up with your own fart joke here).  Dr. Jackson believes at least part of the spike is "almost certainly" coming from livestock and specifically cattle.  More broadly, increased levels of methane are the result of human activity:  Atmospheric concentrations of methane have grown from about 700 parts per billion in the pre-industrial era to more than 1,840 parts per billion today. 

As a greenhouse gas, methane acts more quickly than carbon monoxide:  Additional amounts of it will cause global temperatures to increase faster in the coming decades, threatening to break the threshold agreed upon in the Paris Climate Accord, 2 C degrees over the pre-industrial average.  On the plus side, temperatures would also return just as quickly as methane levels decrease, making this facet of the global warming crisis easier to manage - IF nations deicde to act.