Climate scientists warned that levels of atmospheric carbon dioxide (CO2) is going to be at its highest this year.

Contrary to what experts have previously estimated, CO2 levels will exceed a benchmark of 400 parts per million (ppm) for the entire year, as measured atop Hawaii's famous Mauna Loa volcano.

As explained in the report published in the journal Nature Climate Change, the dramatic escalation can be blamed to El Niño conditions.

El Niño, as defined by Pacific Marine Environmental Laboratory, is characterized by unusually warm ocean temperatures in the Equatorial Pacific. The temperature anomaly affects the weather patterns in different parts of the world. It can result to increased rainfall across the southern tier of the U.S. and in Peru, and drought in the West Pacific.

For the past months, El Niño has warmed and dried the tropics, limiting the ability of forests to eliminate CO2. At the start of the year, El Niño pushed the temperature at its highest, reaching 1.13°C above the 1951-1980 average.

Furthermore, El Niño has triggered huge wildfires around the world, injecting more CO2 in the air. When drought develops, vegetations are dried out, providing ample fuel for the fires. Wildfires will ignite very easily under such dry conditions and can spread quickly, as explained by North Carolina State University.

While naturally occuring, the El Niño can be intensified by human-induced climate change.

"The atmospheric carbon dioxide concentration is rising year-on-year due to human emissions, but this year it is getting an extra boost due to the recent El Niño event--changes in the sea-surface temperature of the tropical Pacific Ocean. This warms and dries tropical ecosystems, reducing their uptake of carbon, and exacerbating forest fires. Since human emissions are now 25 per cent greater than in the last big El Niño in 1997/98, this all adds up to a record CO2 rise this year." Lead author Professor Richard Betts, of the Met Office Hadley Centre and University of Exeter explained to Science Daily.

The report provides further warning and serves as a reminder that people must do something to ease carbon dioxide emissions. BBC noted that the last time CO2 was regularly above 400 ppm was three to five million years ago, before modern humans existed. 

The research was done as collaboration between the Met Office Hadley Centre for Climate Science and Services in England and UC San Diego's Scripps Institution of Oceanography.