The Azimuth Project
Global warming and greenhouse gas concentrations (Rev #1)


Global warming and GHG concentrations refers to an ongoing increase in the global average annual temperature in comparision to concentrations of Green house gases (GHG). This page documents a discussion about the corresponding findings.


In a comment in the Azimuth Forum John Baez mentioned the article:

• Ole Humluma, Kjell Stordahlc, Jan-Erik Solheimd, The phase relation between atmospheric carbon dioxide and global temperature, Global and Planetary Change 100 (2013), 51–69,

which claims to show temperature changes precede changes in carbon dioxide concentration.

The article has a response on the blog realclimate:

El Nino’s effect on CO2 causes confusion about CO2′s role for climate change — rasmus @ 11 September 2012

which critizeses the findings.


The article by Ole Humluma et al. provides the following chart

humlum co2 temperature phase

which was sort of reproduced by realclimate:


where it was sofar not clear to the author of this Azimuth entry what DIFF12 means.

The US based “National climatic data center NOAA” provides the following chart in this context:

Temperature change and carbon dioxide change

NOAA chart temperature vs co2

which displays that co2 concentrations are sometimes lagging behind and sometimes precede temperature changes.

The data is here however not directly measured (since the data goes back to 450 000 ys), which may explain why the the “lagging behind” or “preceding” looks as being sometimes in the range of 10000-30000 years.

In this context it was pointed out that it would also be interesting to see charts of other green house gases vs. temperature. In particular the co2 concentration seems to be connected with the methane concentrations. On the wikipedia page: Atmospheric methane it was pointed out (23.02.2013) that:

Methane is created near the Earth’s surface, primarily by microorganisms by the process of methanogenesis. It is carried into the stratosphere by rising air in the tropics. Uncontrolled build-up of methane in the atmosphere is naturally checked — although human influence can upset this natural regulation — by methane’s reaction with hydroxyl radicals formed from singlet oxygen atoms and with water vapor. It has a net lifetime of about 10 years, (39) and is primarily removed by conversion to carbon dioxide and water.

where the reference (39) is:

Boucher, Olivier; Friedlingstein, Pierre; Collins, Bill; Shine, Keith P (2009). “The indirect global warming potential and global temperature change potential due to methane oxidation”. Environmental Research Letters 4 (4): 044007. Bibcode 2009ERL…..4d4007B. doi:10.1088/1748-9326/4/4/044007.