Carbon dioxide emission
Smoke rises from a chimney of a steel plant next to residential buildings on a hazy day in Fengnan district of Tangshan, Hebei province in this February 18, 2014 file photo. Reuters/Petar Kujundzic/Files

For the first time in history, the monthly average of carbon dioxide levels in the northern hemisphere has exceeded 400 parts per million (ppm) in April, according to the World Meteorological Organization (WMO).

In its news information, the WMO, a specialized agency of the United Nations, cited this symbolic occurrence "is a wakeup call about the constantly rising levels of this greenhouse gas, which is released into the atmosphere by burning fossil fuel and other human activities. This is also believed as the main driver of climate change. Carbon dioxide remains in the atmosphere for thousands of years, trapping heat and causing our planet to warm further, impacting in all aspects of life on earth.

Several Global Atmosphere Watch stations, including the U.S. National Oceanic and Atmospheric Administration, the oldest measurement station in the world have recorded carbon dioxide concentrations topping the threshold.

The WMO explained since pre-industrial times, CO2 levels in our atmosphere have increased by over 40 percent from around 278 ppm. CO2 is the most important greenhouse gas emitted by human activity and responsible for 85 percent of the increase in radioactive force causing the global warming effect in our climate.

"This should serve as yet another wakeup call about the constantly rising levels of greenhouse gases which are driving climate change. If we are to preserve our planet for future generations, we need urgent action to curb new emissions of these heat trapping gases," WMO Secretary-General Michel Jarraud said in a statement.

"Time is running out," he added.

This is becoming a global phenomenon with the same increasing trend even at lower latitudes. WHO noted global observing stations in Cape Verde, Germany, Ireland, Japan, Spain (Tenerife) and Switzerland all reported monthly mean concentrations above 400 ppm in March and April. This should serve as a stark reminder of the urgent need to curb the rapidly rising greenhouse gas emissions.

For more information, a summary of current climate change findings and figures is available here.