Climate Change Caused by Humans
Fiction: CO2 Lags Temperature

Fiction: CO2 Lags Temperature

The claim: Historically, temperature warms first and then CO2 follows (600 years later) so increasing CO2 does not cause global warming.

Figure 1 (Woods Hole Research Center, 2009) shows 400,000 years of carbon dioxide concentrations and temperature change taken from ice core data.

CO2 vs. Temperature Change from Ice Cores
Figure 1: 400,000 years of carbon dioxide concentrations and temperature change

Upon close examination of this record, it appears that temperature warmed first and was then followed by increases in CO2. This is ONLY true BEFORE the Industrial Revolution (IR). Before the IR, humans were not emitting CO2 to the atmosphere so only natural changes could have caused CO2 changes and these changes occurred over thousands of years. As shown in Natural Causes of Climate Change: Orbital-Scale Changes, changes in the orbit of the Earth around the sun (eccentricity) combined with changes in the tilt of the earth (obliquity) caused the 100,000 year cycle of warming and cooling. Once the earth warmed, the warmer oceans outgassed more CO2 and warmer soils outgassed methane which then caused more greenhouse warming. As more and more ice melted, the earth's albedo (reflectivity) decreased which further exacerbated the warming. CO2 may not have caused the initial warming but it definitely drove the climate later on.

Today human activities are driving the CO2 change on very short time scales. CO2 concentrations are known accurately for the past 650,000 years. During that time, they varied between 180 ppm and 300 ppm. As of 10/2009, CO2 is 385 ppm which took about 100 years to increase. For comparison, it took over 5,000 years for an 80 ppm rise after the last glacial period. Higher values than today have only occurred over many millions of years so it is foolish to consider that the natural cycle has any bearing on what is happening today.

CO2 Lags Not Leads CrockPeter Sinclair's Climate Crock of the Week: The "Temp Leads Carbon" Crock
Watch this video which shows why the "CO2 lags temperature" argument is moot today.

Scott A. Mandia
Professor - Physical Sciences
T-202 Smithtown Sciences Bldg.
533 College Rd.
Selden, NY 11784
(631) 451-4104

Last updated: 11/23/09