Nitrous oxide is best known as the mild anesthetic laughing gas, but making people feel a bit loopy during dental surgery is the least of its effects. The gas can warm our planet 300 times faster than carbon dioxide.
The good news is that the amount of nitrous oxide in the atmosphere is totally insignificant compared to the amount of carbon dioxide. The bad news is that could soon change, as a "pulse" of nitrous oxide sometime later this century could send global warming into overdrive. That's what happened in Europe about 14,500 years ago, right at the end of the most recent ice age, and there's reason to think that the environment processes needed for it to happen again have already been set into motion.
As New Scientist reports, a team led by Mirjam Pfeiffer of the Swiss Federal Institute of Technology has discovered that the plants that prospered as the Ice Age began to thaw were ones that converted nitrogen into necessary nutrients, releasing nitrous oxide as a byproduct. In particular, a nitrogen-consuming shrub known as sea-buckthorn totally dominated ancient Europe. The uptick in nitrous oxide wasn't all that much — they estimate an extra 1.6 milligrams of the gas per year in each square meter covered by the shrub — but over time, that was enough to leave a noticeable impact in the geological record, and all that laughing gas might well have accelerated the end of the Ice Age.
It's harder to know what impact all this could have today, but the researchers point out that Arctic ice is receding all the time, exposing land that would make the perfect environment for plants like sea-buckthorn. This could prove a serious problem in the second half of the 21st century, although it's still too early to know for sure just how much impact the gas could have on global temperatures.