Atmospheric levels of carbon dioxide (CO2) have hit a new threshold that hasn't been seen in at least the last 3 million years. In 2015, global average temperatures were 400 parts per million (ppm), but increased to 403.3 ppm in 2016 — caused by emissions from human activities and in parallel with a strong El Niño event in 2015/2016. The data, collected by the World Meteorological Organisation's (WMO) Global Atmosphere Watch program, indicate that atmospheric CO2 levels are now 145 percent higher than pre-industrial levels, while methane and nitrous oxide are sitting at 257 percent and 122 percent, respectively. The contribution to the record-breaking increase from El Niño is unknown, as the event triggers droughts that reduce the ability of natural carbon sinks like forests and oceans to absorb CO2. To find out more check out The State of Greenhouse Gases in the Atmosphere Based on Global Observations through 2016.