Courting disaster

The news last week that the amount of carbon dioxide in the atmosphere produced by the burning of fossil fuels had passed the symbolic milestone of 400 parts per million was a stark reminder that global warming poses the greatest long-term challenge facing humankind, and that we are failing to meet it.

As it turned out, the reading later was revised, as CO2 readings often are, downward to 399.89 ppm, but the point was made: We are courting planetary disaster.

At the beginning of the industrial era, in the 18th century, when humans began burning fossil fuels in earnest, the level was 280 ppm. For the previous 800,000 years, CO2 levels never exceeded 300 ppm, and there is no known geologic period in which rates of increase have been so sharp.

In 1958, a scientist named Charles David Keeling began measuring CO2 levels at the Mauna Loa Observatory, high up on an extinct Hawaiian volcano where local sources have little effect on the air. His initial reading was 313 ppm.

Since then, Keeling and his successors have been charting the increases in CO2 on a daily basis. “I wish it weren’t true, but it looks like the world is going to blow through the 400-ppm level without losing a beat,” said Ralph Keeling, a geochemist who has taken over the measurements from his late father. “At this pace we’ll hit 450 ppm within a few decades.”

Most scientists believe that, while life on Earth can survive an overheated planet, many of its creatures, including humans, will suffer the consequences of drought, disease, conflict over resources such as water, rising sea levels, heat waves and other forms of extreme weather.

Right now we’re in denial about global warming. Even those of us who accept it as reality aren’t changing our ways. But if we don’t change them, nature will change them for us.