As has been widely reported, the concentration of CO2 in the atmosphere from all sources reached 400 ppm this last week. A variety of people have suggested that passing this “milestone” signals our failure to deal with climate change. Actually, reaching this milestone does something quite different. Since there has been no significant warming for seventeen years[i] and none predicted by the UK Met Office until after 2017[ii]; since, according to the IPCC, there is no connection between extreme weather events and climate change[iii]; and since the population has continued to grow as C02 increases, this milestone really signals that the simplistic theory that man-made greenhouse gas “causes” global warming is not as viable a theory as many once thought it was.
The planet has had much higher levels of CO2 before – twenty times higher than the current concentration[iv]. The difference this time is that humans are a dominant species and we have been encouraged to see CO2 as “problematic” rather than the life force that it really is. CO2 at 400 ppm will accelerate plant growth, enabling faster absorption of CO2. It is likely that the average CO2 for 2013 will be not much different from that of 2012 – around 393 ppm.
The ice core samples and other evidence all suggest that, as the temperature rises, more CO2 is produced causing further warming. What we have here is something different. CO2 levels have risen significantly since 1900 but the temperature rise has not been linear. Between 1900 and the present, warming is thought to be around 0.7C. A recent peer reviewed study suggests that if, as some now predict, CO2 reaches 560 ppm by 2100 total warming over two centuries would be around 1.1 degrees – 0.4C warmer than the present[v]. A doubling of CO2 will not produce a massive shift in climate.
There is also a view among some scientists that the sensitivity of the climate to CO2 is much less than previously thought. Stephen Schwartz of Brookhaven National Lab concludes that the Earth’s climate is only about one-third as sensitive to carbon dioxide as the IPCC (Intergovernmental Panel on Climate Change) assumes, suggesting that the 400 ppm milestone is of very little significance.
Much of the science that sees 400 ppm as problematic is what we refer to as “virtual science” – science by model and machine. Dr. Jim Renwick, formerly a top UN IPCC scientist, has suggested that climate models do not account for half the variability in nature and thus are not reliable. "Half of the variability in the climate system is not predictable, so we don’t expect to do terrifically well”, he has said[vi]. Others point to the last seventeen years of no significant warming and point out that none of the twenty one climate models predicted this or can explain this.
Now that, using observation and evidence, we can see that high levels of CO2 are not leading to “catastrophic warming” – observations we can connect to related observations in science (e.g. the medieval warm period was warmer than the present, extended from Europe as far as Antarctica when C02 was considerably less than at present[vii]) - it is time to revisit the theory which is informing our understanding of the climate.
Keynes, speaking to an opponent during Bretton Woods, said “When the facts change, I change my mind. What do you do, sir?” - seems like an appropriate quote here. We are at 400 ppm. There is only modest warming in over a century and none for almost twenty years and none forecast for another 4. CO2 is rising faster than anticipated. What do you do sir?
[iv] Nasif Nahle. 2007. Cycles of Global Climate Change. Biology Cabinet Journal Online. Article no. 295. http://www.biocab.org/Climate_Geologic_Timescale.html, and http://www.biocab.org/Carbon_Dioxide_Geological_Timescale.html. (But also see Vandenbroucke, T.R.A., Armstrong, H.A., Williams, M., Paris, F., Zalasiewicz, J.A., Sabbe, K., Nolvak, J., Challands, T.J., Verniers, J. & Servais, T. 2010. Polar front shift and atmospheric CO2 during the glacial maximum of the Early Paleozoic Icehouse. PNAS doi/10.1073/pnas.1003220107).