Atmospheric carbon dioxide levels have hit their highest level in 800,000 years, with the Mauna Loa Observatory in Hawaii recording concentrations of 410 parts per million (ppm) for an entire month in April for the first time in recorded history.
The last time atmospheric CO2 levels were this high, U.S. meteorologist and climate hawk Eric Holthaus notes, “humans didn’t exist”.
“It’s another milestone in the upward increase in CO2 over time. It’s up closer to some targets we don’t really want to get to, like getting over 450 or 500 ppm,” said Ralph Keeling, director of the Scripps Institution of Oceanography CO2 program. “That’s pretty much dangerous territory.”
“As a scientist, what concerns me the most is what this continued rise actually means: that we are continuing full speed ahead with an unprecedented experiment with our planet, the only home we have,” tweeted climate scientist Katharine Hayhoe.
“The latest reading shows a 30% increase in carbon dioxide concentration in the global atmosphere since recording began in 1958. The first measurement was recorded as 315 ppm,” The Independent notes. “Prior to 1800, atmospheric CO2 averaged about 280 ppm, which demonstrates the effect of manmade emissions since the industrial revolution. Scientists believe the world has never experienced a rise in CO2 levels as quick or intense as this.”
Last year, the World Meteorological Organization said concentrations above 400 ppm—a threshold recorded in 2013—“exceed the natural variability seen over hundreds of thousands of years.” CO2 last reached that level three to five million years ago, during the mid-Pliocene era, the WMO added.
“During that period, global mean surface temperatures were two degrees warmer than today, ice sheets in Greenland and West Antarctica melted, and even parts of East Antarctica’s ice retreated, causing the sea level to rise 10 to 20 metres higher than that today.”
In a Climate Desk post picked up by National Observer, Holthaus warns that “the increases are increasing”, with atmospheric CO2 concentrations rising faster now than they were 50 years ago.
“That’s happening for several reasons, most important of which is that we’re still burning a larger amount of fossil fuels each year,” he writes. “Last year, humanity emitted the highest level of greenhouse gas emissions in history—even after factoring in the expansion of renewable energy. At the same time, the world’s most important carbon sinks—our forests—are dying, and therefore losing their ability to pull carbon dioxide out of the air and store it safely in the soil. The combination of these effects means we are losing ground, and fast.”