Atmospheric oxygen has dropped, according to a study published in the journal Science. Analysis show that oxygen has declined by up to 0.7 percent over the past 800,000 years.

The study involved analyzing air bubbles trapped in ice from Antarctica and Greenland. According to Princeton University geologist Daniel Stolper, they were not expecting the results but this should not alarm anyone as there is still enough oxygen around.

Ecosystems are not expected to be affected by this minute decline in oxygen level but the research team cannot explain what exactly caused it. They plan to find out what caused the drop so we could also predict what would happen to oxygen levels in the future.

Nevertheless, several theories that seek to explain this phenomenon have been raised. Among them speculates that it has something to do with geology.

More erosion causes fresh rocks to be exposed to the air. Apparently, these rocks can absorb oxygen through a process known as oxification.

Experts have also theorized that this oxygen level drop might have been caused by climate change. Our planet’s average temperature drop, that happened millions of years before the global warming we experience now, might have increased oxygen’s solubility in the oceans.

Stolper explains, “Alternatively, when the ocean cools, as it has done over the past 15 million years, before fossil fuel burning, the solubility of oxygen in the ocean increases. That is, the oceans can store more oxygen at colder temperatures for a given concentration of oxygen in the atmosphere.”

Stolper adds that oxygen-dependent microbes in the ocean and in sediments can be more active and use oxygen. Consequently, this leaves less oxygen in the atmosphere.

Although the temperature has increased now, this still cannot help oxygen. Experts say that this is because we are using oxygen at a rate much faster than before.

The research team says further research is still required.