Surprising information about CO2 concentrations–something important here… but it’s halfway down the post…

In yesterday’s post I briefly mentioned Alexander Cockburn’s writing about the lack of correlation between CO2 emissions and concentrations (hat tip to pottereaton, who flagged this up in a comment to a previous post). Cockburn wrote, “Now imagine two lines on a piece of graph paper. The first rises to a crest, then slopes sharply down, levels off and rises slowly once more. The other has no undulations. It rises in a smooth, slow arc. The first wavy line is the worldwide CO2 tonnage produced by humans burning coal, oil and natural gas. It starts in 1928, at 1.1 gigatons (i.e., 1.1 billion metric tons), and peaks in 1929 at 1.17 gigatons. The world, led by its mightiest power, plummets into the Great Depression and by 1932, human CO2 production has fallen to 0.88 gigatons a year, a 30 percent drop. Then, in 1933, the line climbs slowly again, up to 0.9 gigatons.

“And the other line, the one ascending so evenly? That’s the concentration of CO2 in the atmosphere, parts per million (ppm) by volume, moving in 1928 from just under 306, hitting 306 in 1929, 307 in 1932 and on up. Boom and bust, the line heads up steadily. These days it’s at 380. The two lines on that graph proclaim that a whopping 30 percent cut in manmade CO2 emissions didn’t even cause a 1 ppm drop in the atmosphere’s CO2. It is thus impossible to assert that the increase in atmospheric CO2 stems from people burning fossil fuels.”

Although Cockburn didn’t extend his research to more recent times, it’s relatively easy to do. The NOAA publishes annual mean CO2 concentrations and the DOE’s CDIAC publishes annual emissions data. And in fact, the lack of 1 to 1 correlation between emissions and concentrations is surprising.

CO2 concentrations have climbed from 338.68 parts per million in 1980 to the current level of 398.55, a rise of about 60 ppm in 35 years, or a bit under 20%. However, although CO2 emissions have varied significantly, the rise in concentrations has in fact been very steady. The average annual rise has been 1.76 ppm (but hold that fact in mind as you read below. It’s important.)

The years with the largest increases in emissions also had most of the largest increase in concentrations, which is a bit reassuring given what follows. The highest increase in concentrations was in 1998, 2.94 ppm and the lowest was in 1993, 0.69 ppm.

We noted yesterday that in 9 years since 1980 that emissions actually fell. In none of those years did concentrations drop. What Cockburn noted about the Great Depression is also true today. In 2009 during the Great Recession, emission declined by 43 million metric tons, due to energy consumption falling by 5 quads and GDP falling by $3 trillion dollars. But concentrations rose by 1.78 ppm, higher than average. In fact, in four of the nine years when emissions fell, concentrations rose by an amount higher than the average.

The beginning of the 80’s was marked by four consecutive years when emissions fell. During those four years CO2 concentrations rose by 6.25 ppm, 10% of the entire rise in concentrations during the period we’re looking at. I find this surprising–I can understand a one-year disconnect between emissions and concentrations, but four? That’s odd.

However, I noticed something else odd in the data that troubles me even more. When a journalist ‘buries the lede’, it means that the most important information in an article is not at the top of the story, but buried deep inside. To an extent, that’s what I’ve done here.

Because looking at the data, I notice that the mean rise in concentrations from 1980 to 1993 has a fairly modest average of 1.45 ppm. However, the average from 1993 to 2013 jumps to 1.96 ppm. Early in the data series, there is only one year over 1.6 ppm increase. In 1994 the increase jumps to 1.75 ppm and from 1994 to 2013 there are only two years with an increase below 1.6 ppm.

Although concentrations have not shown much, if any, effect on surface mean temperatures (the pause is real, after all, even if James Hansen prefers to say temperatures have stalled), the fact that we are emitting very high levels of CO2 is showing up in concentrations.

Here’s the data: