On May 9, the daily mean concentration of carbon dioxide in the atmosphere of Mauna Loa, Hawaii, surpassed 400 parts per million (ppm) for the first time since measurements began in 1958. Independent measurements made by both NOAA and the Scripps Institution of Oceanography have been approaching this level during the past week. It marks an important milestone because Mauna Loa, as the oldest continuous carbon dioxide (CO2) measurement station in the world, is the primary global benchmark site for monitoring the increase of this potent heat-trapping gas.The agency put the current atmospheric concentration of carbon dioxide in historical context:
Before the Industrial Revolution in the 19th century, global average CO2 was about 280 ppm. During the last 800,000 years, CO2 fluctuated between about 180 ppm during ice ages and 280 ppm during interglacial warm periods. Today’s rate of increase is more than 100 times faster than the increase that occurred when the last ice age ended.The announcement by NOAA ended with a sobering warning:
Once emitted, CO2 added to the atmosphere and oceans remains for thousands of years. Thus, climate changes forced by CO2 depend primarily on cumulative emissions, making it progressively more and more difficult to avoid further substantial climate change.
Some like it hot, so they should be happy. However, those who prefer a more temperate earth may not feel like celebrating this new record.
