keeling curve

GENEVA, May 26 (Reuters) - Carbon dioxide levels throughout the northern hemisphere hit 400 parts per million (ppm) for the first time in human history in April, an ominous threshold for climate change, the World Meteorological Organization said on Monday.
By Tom Miles GENEVA, May 26 (Reuters) - Carbon dioxide levels throughout the northern hemisphere hit 400 parts per million
The 400 ppm threshold should be a sobering wake-up call. It is time for us -- individuals, business leaders, and our policy makers -- to accept the science and face the civilization challenging issue of climate change.
The late Charles David Keeling, a renowned scientist affiliated with the University of California, San Diego, began keeping
Atmospheric concentrations of carbon dioxide surpassed a notable milestone this week.