Paper Reviewed
Liu, X. and Chen, J. 2017. CO2 seasonal variation and global change: Test global warming from another point of view. Sciences in Cold and Arid Regions 9: 0046-0053, DOI: 103724/SP.J.1226.2017.00046.

In this posting we review the work of two Chinese scientists, Liu and Chen (2017), who performed a significant and thorough investigation of the relationship between atmospheric carbon dioxide and temperature, challenging the fundamental argument of the IPCC that rising atmospheric CO2 is causing rising global temperature. For the past year and a half a printout of this article has remained buried under a pile of papers on a desk in our office intended for review and posting on CO2 Science. Now, after a long wait (and overdue cleaning of our office), this important work gets the attention it deserves.

Setting the stage for their work, Liu and Chen note that "the core theory of CO2-caused global warming proposed by the IPCC is based on three assumptions: (1) The Earth acts like a greenhouse, and the greenhouse effect of increasing CO2 is capable of raising temperature. (2) The available instrumental temperature records over the last century accurately reflect global temperature trends. (3) The rising atmospheric CO2 is the result of the increasing consumption of fossil fuel." And they go on to say that "the conclusions by IPCC are logical deductions that should be tested and proven (or challenged) by facts."

As their contribution to science, the two scientists thus proceed to present just such a challenge by examining the relationship between temperature and CO2 using data from Mauna Loa, Hawaii and other observing stations across the globe. Their analyses revealed several important findings, which are discussed in detail below, often using direct quotes from the authors' paper.

Finding #1. "The monthly variations in CO2 and temperature at Mauna Loa, Hawaii, do not correlate with each other (R² = 0.0355). From 1958-2013, CO2 rose while temperature remained flat. Hence, we seriously question whether CO2 is the driving force behind temperature variation."

Finding #2. "Both the instrumental CO2 and temperature records at the Mauna Loa, Hawaii, station show seasonal rises and falls. But there is a 6-month difference in seasonal CO2 and temperature fluctuations between the records in the Northern Hemisphere and the Southern Hemisphere. As we know, the reversal of seasons is determined by the changes in solar radiation. Thus, it is most likely that these seasonal rises and falls of both CO2 and temperature are driven by changes in solar radiation."

Finding #3. "By studying the monthly relationship between CO2 and temperature over several decades, we established a theoretical transfer function between CO2 and temperature. Using this function, the rise of 81.86 [ppm] in CO2 at Mauna Loa, Hawaii, between 1958 and 2012 should have resulted in a 72.86 °C rise in temperature, when in fact the temperature only rose -0.62 °C. Thus, we submit that changes in atmospheric CO2 may not be the cause of global temperature changes."

Finding #4. "In contrast to [the] IPCC's suggestion that global temperature rose 0.85 °C over the last century, from 1958 to 2012, temperatures at Mauna Loa, Hawaii, did not rise over this period. Mauna Loa is far from cities, where temperature variations are most affected by the urban heat island effect. Independent studies in North America, Europe, Australia, and China have shown that the urban heat island effect could lead to recorded temperature rises <1 °C. Thus, we suggest that the IPCC's 0.85 °C temperature rise over the last century could be sufficiently explained by the urban island heat effect."

Finding #5. "The global monthly mean temperature produced by GISS (2013) shows a high correlation with Hawaii CO2 (R² = 0.7655). However, R² = 0.024 is obtained by 188 selected records from individual stations around the world. This test indicated global monthly mean temperature showing high correlation with Hawaii CO2 (R² = 0.7655) was inappropriately corrected and calculated during data process[ing]."

In light of all the important findings listed above, Liu and Chen conclude their paper by writing "an untrue picture is therefore created [based on global monthly mean temperature], that CO2 emission by human activity drives global warming."