Review article Global warming and carbon dioxide through sciences Georgios A. Florides ⁎, Paul Christodoulides Faculty of Engineering and Technology, Cyprus University of Technology, P.O. Box 50329, 3603 Limassol, Cyprus abstract article info Article history: Received 17 March 2008 Accepted 15 July 2008 Available online 28 August 2008 Keywords: Carbon dioxide Global warming Palaeoclimate Greenhouse gas Increased atmospheric CO 2 -concentration is widely being considered as the main driving factor that causes the phenomenon of global warming. This paper attempts to shed more light on the role of atmospheric CO 2 in relation to temperature-increase and, more generally, in relation to Earth's life through the geological aeons, based on a review-assessment of existing related studies. It is pointed out that there has been a debate on the accuracy of temperature reconstructions as well as on the exact impact that CO 2 has on global warming. Moreover, using three independent sets of data (collected from ice-cores and chemistry) we perform a specific regression analysis which concludes that forecasts about the correlation between CO 2 - concentration and temperature rely heavily on the choice of data used, and one cannot be positive that indeed such a correlation exists (for chemistry data) or even, if existing (for ice-cores data), whether it leads to a “severe” or a “gentle” global warming. A very recent development on the greenhouse phenomenon is a validated adiabatic model, based on laws of physics, forecasting a maximum temperature-increase of 0.01– 0.03 °C for a value doubling the present concentration of atmospheric CO 2 . Through a further review of related studies and facts from disciplines like biology and geology, where CO 2 -change is viewed from a different perspective, it is suggested that CO 2 -change is not necessarily always a negative factor for the environment. In fact it is shown that CO 2 -increase has stimulated the growth of plants, while the CO 2 -change history has altered the physiology of plants. Moreover, data from palaeoclimatology show that the CO 2 - content in the atmosphere is at a minimum in this geological aeon. Finally it is stressed that the understanding of the functioning of Earth's complex climate system (especially for water, solar radiation and so forth) is still poor and, hence, scientific knowledge is not at a level to give definite and precise answers for the causes of global warming. © 2008 Elsevier Ltd. All rights reserved. Contents 1. Introduction . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391 2. An analysis of the existing climate data . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391 2.1. Temperature-increase during the 20th century . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391 2.2. Carbon dioxide and temperature . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 391 2.3. The debate about the temperature reconstructions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 393 2.4. Dispute about CO 2 being the climate driving factor . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394 2.5. Atmospheric CO 2 -concentration. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 394 3. CO 2 and temperature: the assumed correlation . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 395 4. The adiabatic theory of the greenhouse effect . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 396 5. The geologic record . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 397 6. The CO 2 role in geology and biology . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398 6.1. Earth's atmosphere and the recorded role of CO 2 in geologic strata . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398 6.2. Biological changes due to the change of CO 2 in the atmosphere. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 398 6.3. Plant growth and CO 2 enrichment . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399 6.4. Seasonal variation of CO 2 -concentration related to plant life . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399 7. Conclusions . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 399 References. . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . . 400 Environment International 35 (2009) 390–401 ⁎ Corresponding author. Tel.: +357 25002623; fax: +357 25002769. E-mail address: georgios.florides@cut.ac.cy (G.A. Florides). 0160-4120/$ – see front matter © 2008 Elsevier Ltd. All rights reserved. doi:10.1016/j.envint.2008.07.007 Contents lists available at ScienceDirect Environment International journal homepage: www.elsevier.com/locate/envint