One study .. found “most subjects believe atmospheric GHG concentrations can be stabilized while emissions into atmosphere continuously exceed removal of GHGs from it.” The author, Dr. John Sterman…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.

…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.”

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): IPCC

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… 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.

>more> ClimateProgress/Joe Romm