Leif Svalgard writes:
In 2006 less CO2 was added to the atmosphere than in 1983. In 1980 more CO2 was added to the atmosphere than in 2004. Why is that? Im sure that the worlds human population has increased its output of CO2 significantly since the 1980s. Where did it go? Why does the growth rate change from year to year? Biology? Algae in the sea? I dont know, just asking. And why does nobody else ask this?
I don’t think that it’s accurate to say that “nobody” asks this. The CO2 “sink” has worried many people. Needless to say, this has already led to many responses. This is a topic that many readers are interested in and I’m re-threading the comments to avoid the other thread from getting over-ridden. I do not want the thread to get involved in discussion of the problems with the Beck paper. That’s been amply done. NO discussion of CO2 measurement methods. Just the narrow issue of the sentence above.
It is not a topic that I’ve spent time, but I do not believe that there are any substantive issues as to the existence of increased CO2 levels.
Here are some sensible comments on the matter by Ferdinand Engelbeen on this.
As a result of a lot of discussions about the reliability of CO2 measurements, and the man-made part of the increase, I have made a web page about the basics of CO2 “background” levels and the increase at http://www.ferdinand-engelbeen.be/klimaat/co2_measurements.html, already mentioned by Hans Erren and others in this discussion. Unfortunately, that page is not yet complete, and several arguments which indicate that most of the increase is man-made are not yet in the page. Another part to come is a discussion of Beck’s data/paper, to be added after the base discussion.
That the increase of CO2, at least in the past 50 years, is mainly man-made already follows out of the mass balance (CO2 expressed as gigaton carbon, 1 ppmv change in the atmosphere is about 2.1 GtC in the total air mass):
Csources + Cemissions = Csinks + dCair
where Cemissions = 2.5-6.5 GtC/yr (emissions are increasing over the 50 years)
and dCair = 1-6 GtC/yr (the yearly change of CO2 concentration in the atmosphere in average is increasing over the 50 years)
and Csinks = Csources + 3 GtC +/- 2.5 GtC
That means that, at least over the past 50 years, in every year the increase in the atmosphere was smaller than the emissions. Thus the sum of all possible natural influences (mainly due to temperature variability) in every year was more sink than source. Thus oceans + vegetation can’t be huge sources of CO2, except for a longer term temperature increase/decrease. Theoretically, the oceans or vegetation could be net sources, but then the other one need to be a larger sink to receive the excess CO2 + a part of the emissions.
As already given by Hans Erren, the plot of global lower atmosphere temperatures (UAH) and global CO2 increase rates show a good correlation. As CO2 increase rates follow temperature changes, the main driver is the temperature. For short-term changes (like El Niño 1998, Pinatubo 1992), the change in increase is about 4 ppmv/K. To be noted, that is a change in increase speed, still with a continuous increase in atmospheric CO2.
On longer terms, the ratio is about 8 ppmv/K (Vostok ice core 420,000 years), be it with hundreds to thousands years smoothing, due to the time needed to close the bubbles in firn and the number of layers needed for one CO2 measurement sample. The ratio is about 10 ppmv/K in high accumulation ice cores like Law Dome, with a 60 years smoothing over relative shorter time frames (past 10,000 years). The latter shows about 10 ppmv decrease for the about 1 K temperature decline between the MWP and the LIA. If nothing has changed in the CO2/temperature ratio (there is no indication for that), then the temperature change LIA-current times of about 1 K should have added about 10 ppmv since the LIA. The rest of the 100 ppmv is quite certainly man-made. Or in the time frame since Mauna Loa accurate measurements, about 70% of the emissions were made, which again are responsible for most the increase of CO2 in the atmosphere.
More evidence for man-made increase is in the following:
- CO2 levels in the upper oceans follow the air measurements
- pH levels in the upper oceans are decreasing
- d13C ratios are declining in the atmosphere and with some delay in the upper oceans
This is a good indication that the (deep) oceans are not the source of the extra CO2, as the (deep) oceans have a higher d13C ratio than the atmosphere.
- oxygen levels are declining in near ratio with fossil fuel use.
As there is a small deficiency in oxygen use, that indicates that vegetation is not a net source of CO2, but a net sink (about 2 GtC/yr), as oxygen is produced by CO2 uptake.
The combined observations can be shown in the following graph (made by Bert Bolin) for the last decade of the 1900′s:
That the temperature has a huge influence on CO2 levels is eminent in the seasonal flows: a general exchange of about 100 GtC between oceans and atmosphere occurs over the seasons. For the seasonal exchange between atmosphere and vegetation, the seasonal exchange is about 50 GtC (see e.g. Battle ea. for estimates of seasonal flows between oceans, atmosphere and vegetation). These are huge flows of additions/sinks itself, but the net result at the end of one seasonal cycle doesn’t show much variation: +/- 3 GtC/yr. The net seasonal change in the atmosphere is the result of oceanic release and vegetation uptake in summer and the opposite in winter. This is visible in all 10 base stations which measure CO2 (and all other 400+ stations in the world). The yearly variation is higher in the NH (more land, less ocean) than in the SH, and there is a altitude gradient (Barrow at 7 m: +/- 10 ppmv, Mauna Loa 3,000 m: +/- 5 ppmv), as the main exchanges are at gound level. The SH follows the NH trend with a 6-12 months delay (and increasing). This indicates that the main source is in the NH (where 90% of the emissions are). The ITCZ forms a barrier, which delays the exchange of air (and CO2 and aerosols) between the NH and SH.
The global change in ocean/air/vegetation temperature over the seasons is about 0.2 K (hard to detect in the noise!), I didn’t look at NH alone in a quick search, but if we assume that the NH has a larger winter-summer temperature difference (about 0.5 K, any better bid accepted), then we are back at our long-term estimate of 10 ppmv/K if we take the Mauna Loa data as base. Thus we can safely assume that the variation in increase of CO2 in the atmosphere is due to a quick response of nature (upper oceans and vegetation) to temperature changes.