How do We Know the Rise in Atmospheric Carbon Dioxide Comes from Us?

by Daniel Bailey
(Michigan, United States)

To start with, scientists have a pretty good understanding of what the Earth's climate has been throughout its history, why it has changed over time and what specific factors have caused the climate to change.

In truth, the only factor that fully explains all the changes we can see and measure in temperatures, ocean salinity, atmospheric composition, loss of Arctic sea ice volume, and species habitats & ranges is due to the warming from human-derived fossil fuel, mainly CO₂, that we have put back into the carbon cycle.

Negative Natural Flux

We have accurate, reliable data for the growth of atmospheric CO₂ and for anthropogenic emissions (for details, see Cawley, 2011).

The fact that the net natural flux is negative clearly shows that natural uptake has exceeded natural emissions every year for the last fifty years at least, and hence has been opposing, rather than causing the observed rise in atmospheric CO₂.

• pubs.acs.org

More Carbon Dioxide is Entering the Ocean

It is true that the fluxes between the oceans and atmosphere depend on temperature, so all things being equal, one would expect atmospheric CO₂ to rise in a warming world.

However, the thing the fake-skeptics normally ignore is that CO₂ solubility increases with increasing difference in the partial pressures of CO₂ between atmosphere and surface waters.

In the real world, all things are not equal, our emissions have caused a difference in partial pressures, which is increasing the oceanic uptake, which more than compensates for the temperature driven change in fluxes.

• www.nature.com

Evidence that it is Caused by Mankind

The human-caused (anthropogenic) origin of the measured increase in atmospheric concentrations of CO₂ is a cornerstone of predictions of future temperature rises.

As such, it has come under frequent attack by people who challenge the science of global warming. One thing noteworthy about those attacks is that the full range of evidence supporting the anthropogenic nature of the CO₂ increase seems to slip from sight. So what is the full range of supporting evidence?

There are ten main lines of evidence to be considered:

1. The start of the growth in CO₂ concentration coincides with the start of the industrial revolution, hence anthropogenic;
   
   • radioviceonline.com


2. Increase in CO₂ concentration over the long term almost exactly correlates with cumulative anthropogenic emissions, hence anthropogenic;
   
   • scrippsco2.ucsd.edu
   
   
3. Annual CO₂ concentration growth is less than Annual CO₂ emissions, hence anthropogenic;
   
   • www.globalcarbonproject.org
   
   
   • pubs.acs.org


4. Declining C14 ratio indicates the source is very old, hence fossil fuel or volcanic (ie, not oceanic outgassing or a recent biological source);
   
   • archiv.ub.uni-heidelberg.de


5. Declining C13 ratio indicates a biological source, hence not volcanic;
   


6. Declining O₂ concentration indicate combustion, hence not volcanic;
   


7. Partial pressure of CO₂ in the ocean is increasing, hence not oceanic outgassing;
   
   • serc.carleton.edu


8. Measured CO₂ emissions from all (surface and beneath the sea) volcanoes are one-hundredth of anthropogenic CO₂ emissions; hence not volcanic;
   


9. Known changes in biomass too small by a factor of 10, hence not deforestation;
   
   • www.globalcarbonproject.org
   • web.archive.org


10. Known changes of CO₂ concentration with temperature are too small by a factor of 10, hence not ocean outgassing.
    
    • en.wikipedia.org

Incontrovertible Evidence

The current, and ongoing, increase in atmospheric carbon dioxide concentration is due to human industrial activities.

In scientific circles this is the climatological equivalent of the Earth being round - a fact so plainly obvious and supported by such a vast body of scientific evidence that to question its reality is absurd.

It quickly becomes clear that it is the humans who have caused the rise in CO₂ levels, by burning fossil fuels in the twentieth century. Every other hypothesis makes a host of predictions that do not pass the test of the evidence.