Say What? CO2 Emissions Down. Atmospheric CO2 Up.

March 21, 2016


Joe Romm at ClimateProgress:

Last year saw the biggest jump in global CO2 levels ever measured, as NOAA reported on March 9. Yet in 2015 the world economy grew while energy-related CO2 emissions were flat — for the second year in a row — according to the International Energy Agency, as ClimateProgress reported last week.

This puzzled more than one reader. One emailed me the following: “the IEA is saying that emissions have gone flat, while, at the same time, NOAA is announcing that we just had the largest-ever jump in CO2 [levels]. Logic would seem to dictate that someone has their figures wrong. Flat emissions should not translate into record CO2 jumps.”

What’s going on? Two things:

  • Annual CO2 emissions are very different from global CO2 levels.
  • CO2 levels tend to have big jumps in El Niño years.

Let’s go through those two, especially since this discussion gets to the heart of what I call “the biggest source of confusion in the public climate discussion” in my recent book, “Climate Change: What Everyone Needs to Know.” It also goes to the heart of why delaying action is so dangerous and costly.

The CO2 Bathtub Analogy

Avoiding catastrophic warming requires stabilizing CO2 concentrations (or levels) in the atmosphere, not annual emissions. Studies find that many, if not most, people are confused about this, including highly informed people, mistakenly believing that if we stop increasing emissions, then global warming will stop. In fact, very deep reductions in greenhouse gas emissions are needed to stop global warming.

One study by MIT grad students found that “most subjects believe atmospheric GHG concentrations can be stabilized while emissions into the atmosphere continuously exceed the removal of GHGs from it.” The author, Dr. John Sterman from MIT’s Sloan School of Management, notes that these beliefs “support wait-and-see policies but violate conservation of matter” and are “analogous to arguing a bathtub filled faster than it drains will never overflow.”



While atmospheric concentrations (the total stock of CO2 already in the air) might be thought of as the water level in the bathtub, emissions (the yearly new flow into the air) are the rate of water flowing into a bathtub from the faucet. There is also a bathtub drain, which is analogous to the so-called carbon “sinks” such as the oceans and the soils. The water level won’t drop until the flow through the faucet is less than the flow through the drain.

Similarly, carbon dioxide levels won’t stabilize until human-caused emissions are so low that the carbon sinks can essentially absorb them all. Under many scenarios, that requires more than an 80 percent drop in CO2 emissions. And if the goal is stabilization of temperature near or below the 2°C (3.6 °F) threshold for dangerous climate change that scientists and governments have identified, then CO2 emissions need to approach zero by 2100.

So the first key point is that CO2 levels will continue rising if we merely keep annual CO2 emissions flat. In fact, they will keep rising at a faster and faster rate because the land and ocean carbon sinks are weakening (see below).

The Temporary Impact Of El Niño

NOAA reported two weeks ago that the CO2 concentrations “measured at NOAA’s Mauna Loa Observatory in Hawaii jumped by 3.05 parts per million during 2015, the largest year-to-year increase in 56 years of research.” That is a big jump compared to the average annual rise at Mauna Loa from 2005 to 2014 of 2.11 ppm per year.

But the second-highest single-year growth rate for CO2 levels was back in 1998, which saw a jump of 2.93 ppm (whereas the average annual rise from 1995 to 2004 was 1.87 ppm per year).

You may notice a pattern here — big jumps during big El Niño years.

“El Niño years tend to be bad years for plant growth, due to things like widespread drought or other extreme weather,” Stefan Rahmstorf, co-chair of Earth System Analysis at the Potsdam Institute for Climate Impact Research, explained in an email. “So the biosphere loses some carbon. You see that happening in 1998 as well. Below is a diagram from the AR5, you see from the squiggly line how variable the land sink is, it dominates interannual variability in the carbon budget.”

CO2 emissions

Annual manmade CO2 emissions and where they end up. The partitioning is between the ocean sink (dark blue), the atmosphere (light blue) and the land sink (green).


A crucial point is that, based on actual observations and measurements, the world’s top carbon cycle experts have determined that the land and oceans are becoming steadily less effective at removing excess CO2 from the atmosphere, as I reported last year. This makes it more urgent for us to start cutting carbon pollution ASAP, since it will become progressively harder and harder for us to do so effectively in the coming decades.

In particular, the defrosting permafrost and the resultant release of CO2 and methane turns part of the land sink into a source of airborne greenhouse gases. Similarly, as global warming increases forest and peatland fires — burning trees and vegetation — that also turns one part of the land carbon sink into a source of atmospheric CO2. So does ever-worsening droughts that scientists are observing in the United States southwest and other parts of the world.

We are destroying nature’s ability to help us stave off catastrophic climate change. “Clearly nature is helping us” deal with atmospheric CO2 right now much more than it will be decades to come, as Dr. Josep (Pep) Canadell, executive director of the Global Carbon Project, told me last year. Ultimately this is one more reason why delaying action to cut carbon pollution is a costly and dangerous mistake.


7 Responses to “Say What? CO2 Emissions Down. Atmospheric CO2 Up.”

  1. (1) Complicated systems have lags between forcings and responses.

    (2) CO2 is not the only greenhouse gas: While not at historical highs, atmospheric concentrations in methane (CH4) have trended significantly upwards in recent years. These have been tied in no small measure to oil and natural gas production in North America and Europe.

  2. grindupbaker Says:

    I assumed it would be more warmer tropical Pacific Ocean surface CO2 release with no more polar, sub-polar CO2. Shows how useless my hunches are. I dislike the dangerous bath-tub analogy, saw Dr. Sarah Gilles nearly drown explaining it in a South Polar oceans talk. Nobody wants to hear my superior constipated atmosphere analogy even though it resonates well. It isn’t really a “climate lag” in the sense that I’ve ever used “lag”, it’s a “convolution”. A lag is a convolution with a spike filter only (with zeros prior to the spike creating a lag. This is a complex filter determined by thermal inertia and ocean mixing and whatnot (especially whatnot is a big part of climate). Some increasing %age is realized after 1, 2, 5, 10, 20, 50, 100 years (and the ones between). The classic “lag” I know is that between impressed A.C. voltage and resulting A.C. current in a circuit with inductive or capacitive load. If one ~sine wave is shifted by he lag then it almost perfectly overlays the other ~sine wave.

  3. rabiddoomsayer Says:

    Inevitable and well understood for a long time. This is not new science. The slowing of the sinks was always going to happen and the reversal of the drain is also going to happen. The natural systems will become a source of CO2. Happened every time in the past, at the end of every ice age, and will happen again.

    Mankind’s control of the leavers is close to ending, exactly when is an unknown.

  4. redskylite Says:

    The speed/rate at which we have loaded up our atmosphere with CO2 is the most terrifying aspect, a recent study can find no analog/parallel in nature.

    A few years back, an authoritative symposium calculated at 450 ppm CO2 there was only a 50% chance we would stay under 2 degrees Celsius of warming. We must be getting very close to the mark now.

    There is good reason for alarm.

    “The rate of carbon emissions during a period of abrupt warming 56 million years ago was ten times slower than current emissions from the burning of fossil fuels and other human activities, according to a new study published in Nature Geoscience. The study shows that the current rate at which carbon is being released into the atmosphere is unprecedented in at least the past 66 million years.

    Evidence found in sediment cores from the seafloor shows that 56 million years ago, massive emissions of greenhouse gases, possibly triggered by volcanism, caused a global warming of at least 5 degrees Celsius. Climate scientists have considered this episode, known as the Paleocene-Eocene Thermal Maximum (PETM), the closest analogue to current climate change. But the actual magnitude and rate of carbon emissions during the PETM have been difficult to determine.”

  5. Julian Bond Says:

    – Large quantities of salt are needed and a sceptical mind
    – The IEA has skin in the game
    – It’s “energy related emissions” which basically means electricity.
    – So it probably ignores construction, manufacturing, agriculture and shipping
    – The figures are heavily dependent on accurate reporting from China.
    – Looking for 0.1% changes in global figures that are apt to be adjusted later by 17% by China is a problem.
    – Same goes for global GDP figures. So be sceptical of uncoupling stories
    – CO2 emissions are at their highest ever level. But they only stayed at the same highest level for 2 years instead of increasing. Hooray!

    It would be better to see accurate reporting of accurate statistics prepared by neutral parties who don’t have skin in the game. Explained by accurate and non-sensational journalism that doesn’t try to sell advertising by hyping a questionable conclusion. But that’s all too much to hope for, right. Hence the need for large grains of salt and a bit of fact checking. 😉

    And especially, beware stories that say it’s not quite as bad as we thought it might be. Dig a bit deeper and it often turns out it’s just as bad as we thought it was.

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