Washington ? Carbon dioxide isn’t the only greenhouse gas that worries climate scientists. Airborne levels of two other potent gases – one from ancient plants, the other from flat-panel screen technology – are on the rise, too.

And that’s got scientists concerned about accelerated global warming.

The gases are methane and nitrogen trifluoride. Both pale in comparison to the global warming effects of carbon dioxide, produced by the burning of coal, oil and other fossil fuels. In the past couple of years, however, these other two gases have been on the rise, according to two new studies. The increase is not accounted for in predictions for future global warming and comes as a nasty surprise to climate watchers.

Methane is by far the bigger worry. It is considered the No. 2 greenhouse gas based on the amount of warming it causes and the amount in the atmosphere.

Methane comes from landfills, natural gas, coal mining, animal waste, and decaying plants. But it’s the decaying plants that worry scientists most. That’s because thousands of years ago billions of tons of methane were created by decaying Arctic plants. It lies frozen in permafrost wetlands and trapped in the ocean floor. As the Arctic warms, the concern is this methane will be freed and worsen warming. Scientists have been trying to figure out how they would know if this process is starting.

The other gas, nitrogen trifluoride, is used as a cleaning agent during the manufacture of liquid crystal display television and computer monitors and for thin-film solar panels.

Nitrogen trifluoride levels – measured in parts per trillion – have quadrupled in the last decade and increased 30-fold since 1978, according to the studies.

The studies will be published in the journal Geophysical Research Letters next Friday.