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Who Or What Is The Real Culprit? 1 May , 2007

Posted by eugene in 6 Use Rights as Citizens & Consumers.

Mr Andy Ho, Senior Writer for The Straits Times, wrote an article today in the Review section titled, “Who or what is the real culprit?“, to debunk man-made global warming. I wrote a letter to the ST Forum on my views to explain why I disagree with him. I think my letter will not be published as it is too long, so I’m sharing the contents of my unpublished letter that I submitted.

I’m not an expert on global warming and my explanations are based on my limited knowledge. Most of the global warming science that I read comes from the IPCC report, RealClimate, and some published papers.


Man is the real culprit 

I refer to the article, ‘Who or what is the real culprit?’ by Mr Andy Ho (ST, May 1). 

Mr Ho discussed three main points to debunk man-made global warming. One, there is no scientific consensus. Two, there is contradictory evidence and other causes. Three, it is caused by the sun. He is entitled to his views but I will offer my views to explain why I disagree with him. 

In my opinion, there are two ways in which people reach consensus on global warming – after looking at the evidence or after hearing what other people say. To show that there is no consensus, Mr Ho quotes three scientists – Richard Lindzen, John Christy and Paul Reiter. Through their quotes in the press and the documentary, The Great Global Warming Swindle, Mr Ho suggests that there is no consensus among scientists and even within the IPCC.  

On the other hand, I can show scientific consensus by listing national science academies that agree with man-made global warming and they include: National Academy of Sciences (United States of America); Science Council of Japan; Russian Academy of Sciences; Australian Academy of Sciences; Royal Flemish Academy of Belgium for Sciences and the Arts; Brazilian Academy of Sciences; Royal Society of Canada; Caribbean Academy of Sciences; Chinese Academy of Sciences; French Academy of Sciences; German Academy of Natural Scientists Leopoldina; Indian National Science Academy; Indonesian Academy of Sciences; Royal Irish Academy; Accademia Nazionale dei Lincei (Italy); Academy of Sciences Malaysia; Academy Council of the Royal Society of New Zealand; Royal Swedish Academy of Sciences; and Royal Society (UK). 

Incidentally, the documentary has received complaints of being misleading and one-sided. In addition, a professor of physical oceanography at MIT who gave comments in the documentary, is considering legal action against the producers after saying his comments were taken out of context to mislead people that man-made global warming is not real. He believes that climate change is real, a major threat, and almost surely has a major human-induced component”. 

So who is right? People have different views on issues, therefore, consensus should not be based on who is saying what but should be based on scientific evidence. This brings me to Mr Ho’s second point. 

The evidence that Mr Ho presented says that temperature rise precede carbon rise by 800 years. Carbon dioxide is not causing global warming and the culprit could likely be water vapour, methane or nitrous oxide. Mr Ho’s point is that carbon dioxide is not causing higher temperatures, therefore humans are not the cause of global warming. 

What causes global warming? To answer that, we need to first understand the concept of radiative forcing and that carbon dioxide is not the only cause of global warming. According to the IPCC report, radiative forcing is “a measure of the influence that a factor has in altering the balance of incoming and outgoing energy in the Earth-atmosphere system and is an index of the importance of the factor as a potential climate change mechanism. Positive forcing tends to warm the surface while negative forcing tends to cool it”.

Different radiative forcing sources include carbon dioxide, mehane, nitrous oxide, ozone, surface albedo, aerosols and solar irradiance. Warming or cooling periods in the past are affected by the contribution from each forcing source, and is decided by the forcings that dominate or is amplified. Carbon dioxide is the dominant contribution to positive radiative forcing in recent times due to emissions from human activities, which is why it contributes mainly to global warming.  

The idea that temperature rise precede carbon rise is not new and can be found in several published papers. In a paper published in Science magazine by Caillon et al. (2003), it was stated that “the 800-year time lag is short in comparison with the total duration of the temperature and CO2 increases (~5000 years)”. It takes about 5000 years for glacial-interglacial warming to happen and if the first 800 years of temperature rise is not caused by carbon rise, we cannot conclude that the remaining 4,200 years is not caused by carbon rise. The first 800 years of warming could be due to one or more of the other radiative forces besides carbon dioxide, and then amplified by the radiative forcing due to carbon dioxide for the other 4,200 years. Therefore, the 800-year lag cannot conclude that carbon dioxide is not causing global warming.                                                                                                                                

Mr Ho suggest that the global warming culprit could be other gases because methane is 27 times more powerful than carbon dioxide as a greenhouse gas, and water vapour and nitrous oxide are each 380 times more powerful. According to the IPCC report, the atmospheric concentration of carbon dioxide in 2005 is 379ppm, methane is 1.774ppm, and nitrous oxide is 0.319ppm. Carbon dioxide still exerts greater radiative forcing than methane and nitrous oxide because it is in higher concentrations.                            

The IPCC includes water vapour in its climate models, although not as a radiative forcing but as a feedback. Although water vapour makes up the bulk of greenhouse gases, it is considered as a feedback because it has conflicting feedbacks on the greenhouse effect, and it also does not stay in the atmosphere for a long time. Water vapour has a positive feedback by acting as a greenhouse gas and causing warming but it also has a negative feedback when it becomes clouds and reflecting solar radiation, thus causing cooling.     

The third point by Mr Ho is that global warming is caused by the sun. He is partly right, global warming is caused by the sun and the associated water vapour and clouds, but they are not the dominant culprit. The Earth is warmed by the sun and has an effect on climate. According to the IPCC report, “changes in solar irradiance since 1750 are estimated to cause a radiative forcing of +0.12 W/m2”, compared to total net anthropogenic radiative forcing of +1.6 W/m2. Human activities still play a bigger role than the Sun. In addition, a review paper in Nature by Foukal et al. (2006) concluded that “brightening of the Sun is unlikely to have had a significant influence on global warming since the seventeenth century”.                                                                                             

The existing evidence and explanations available is sufficient to convince myself that recent global warming is caused by human activities. I hope that Mr Ho and other readers will not accept everything I say but to look at the scientific evidence and explanations, and then make up their mind on whether recent global warming is man-made and what actions to take.

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