Seasonal CO2 Minimum May Have Passed

In addition to a steady, long-term climb, the level of CO2 in the atmosphere varies by season - dropping in summer and climbing in winter. It looks like we have passed the seasonal minimum and the level is climbing again. The Keeling Curve, the plot of measurements taken at Mauna Loa, Hawaii, normally turns upwards around the beginning of October and is now doing so. The latest daily measurement was 395.58 ppm on October 5. Here is a plot of the measurements for the last two years:

Source: SIO

You can see how the curve has turned upwards as well as the year-to-year increase. What is disturbing about this plot is how much it is climbing. Last year, it made news when the level topped 400 ppm. This year, that level was passed for three months in a row. This coming year will see it passed for at least five months. I believe it will be only another three years before we reach the point when the minimum will not drop below 400 ppm. By the end of 2017, we will never again see the level drop below 400 ppm.

Here is the plot of the long-term data:

Source: SIO

The 395 ppm level was first touched just three years ago. That means prior to 2011 the CO2 level had not reached 395 ppm at anytime in at least the last 800,000 years. Now, it doesn't drop below that level.

In mean time, contrarians and the denial industry will tell you we don't need to do anything.