Like many people I often search for simple answers to complex problems, call it a typical human failing. Unfortunately human induced global warming defies such a simplistic approach but I have at least found a concise and accurate description of how it works.
“The way the greenhouse effect really works is that adding CO2 reduces the infrared out the top of the atmosphere, which means the planet receives more solar energy than it is getting rid of as infrared out the top. The only way to bring the system back into balance is for the whole troposphere to warm up. It is the corresponding warming of the low level air that drags the surface temperature along with it …” Ray Pierre January 2010.
How did we get to this concise definition? Years of hard work by thousands of dedicated scientists across the globe, that's how!
In 1908, Nobel Laureate Svante Arrhenius was the first scientist to predict that emissions of carbon dioxide from the burning of fossil fuels would cause global warming. Arrhenius estimated that a doubling of CO2 would cause a global temperature rise of 2.1°C.
At that time atmospheric CO2 levels were approximately 280 parts per million (ppm) and are now at 387.27ppm. Modern estimates are that a doubling of CO2 concentrations (against a 1900 baseline) would result in a global temperature rise of approximately 3°C and that a 2°C rise would occur at 450ppm. There are definitely alternative estimates but I take these to be 'mainstream' for the sake of this discussion.
Our modern understanding of the role of artificially produced CO2 in climate change is based on the work of many scientists including that of Guy Callender. A close reading of Callender's paper reveals a basic understanding of the process by which CO2 might impact on climate was in place more than 80 years ago!
To me Callender's paper is a strong reminder that, far from being a new topic, the likely effects of carbon dioxide on global climate have been recognized for many decades. Callender concluded that global temperature had already observably increased as a result of human activity way back in 1938! His findings were not widely accepted then, but the intervening 80 years of research and peer review has resulted in his basic concepts gaining wide acceptance.
In 1972 atmospheric scientist J. S. Sawyer published Man-made Carbon Dioxide and the “Greenhouse” Effect (Nature 239, 23-26; 1972). Sawyer summarized what was then known about the role of carbon dioxide in enhancing the natural greenhouse effect, and made a prediction of warming at the end of the twentieth century being an increase of 0.6 °C in world temperature. In fact the global surface temperature rose about 0.5 °C between the early 1970s and 2000 (N Nichols, Nature 448, 992 30 2007).
The scientific consensus on global warming as a result of increasing atmospheric carbon dioxide concentrations has developed over the past 100 years. Today, large amounts of data, improved models and analyses allow more informed and relevant discussion of man induced climate change.
Of course there are errors and false assumptions made along the way but, by enormous effort, the science has advanced and understanding has improved, and that is how science is supposed to work!
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Like many people I often search for simple answers to complex problems, call it a typical human failing. Unfortunately human induced global warming defies such a simplistic approach but I have at least found a concise and accurate description of how it works.
