But he sure could waste a lot of time, money and effort trying.
Some form of the graph below is probably what persuades most laymen that increased carbon dioxide in the atmosphere causes global warming. But what does it really tell us?

SOURCE:
Eye-opener on Global Warming
1) This graph does not prove causation. It could equally be said to prove that "global warming" causes increased atmospheric CO2. It could also be that both are caused by some other factor or factors.
2) The temperature anomaly (amount of "global warming") did not increase between 1960 and 1978. In fact, during that period, it would have been called "global cooling". But Atmospheric CO2 rose from 320 ppm to almost 340 ppm.
3) The temperature anomaly peaked in 1998 (ten years ago!), yet atmospheric CO2 continued to rise.
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CO2 is not the major "greenhouse gas". Water vapor is the most effective and by far most abundant "greenhouse gas", accounting for about 95% of the greenhouse effect, and it is 99.999% of natural origin.
There are LESS THAN 400 parts per million in our atmosphere. That is not much.
Not only that, but the great majority of carbon dioxide is NOT man made.
Source of two above graphs:
Global Warming: A Closer Look At the Numbers
In short, global warming, such as it is, is NOT caused by man or by carbon dioxide.
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It’s not even certain how much atmospheric carbon dioxide has increased. Scientists were directly measuring CO2 concentration all during the 19th century, as shown below.

SOURCE: http://www.john-daly.com/zjiceco2.htm
When you remember that atmospheric CO2 concentration today is below 380 ppm, maybe there really has NOT been a big increase.
Today, scientists use microscopic air bubbles trapped in ice cores to estimate past CO2 concentrations, which gives a lower estimate for the 19th century. However, this method has many possible flaws. According to Professor Jaworowski, this results in:
False Low Pre-industrial CO2 in the Atmosphere
Determinations of CO2 in polar ice cores are commonly used for estimations of the pre-industrial CO2 atmospheric levels. Perusal of these determinations convinced me that glaciological studies are not able to provide a reliable reconstruction of CO2 concentrations in the ancient atmosphere. This is because the ice cores do not fulfill the essential closed system criteria. One of them is a lack of liquid water in ice, which could dramatically change the chemical composition the air bubbles trapped between the ice crystals. This criterion, is not met, as even the coldest Antarctic ice (down to -73°C) contains liquid water[2]. More than 20 physico-chemical processes, mostly related to the presence of liquid water, contribute to the alteration of the original chemical composition of the air inclusions in polar ice[3].
SOURCE: Climate Change: Incorrect information on pre-industrial CO2
Statement written for the US Senate Committee on Commerce, Science, and Transportation March 2004
Statement of Prof. Zbigniew Jaworowski
Chairman, Scientific Council of Central Laboratory for Radiological Protection
Warsaw, Poland
See also CO2: The Greatest Scientific Scandal of Our Time
CONCLUSION: Let’s quit wasting our time demonizing carbon, and hold the global warming panic until we really know the cause of temperature fluctuations. There is also credible evidence that earthly temperature changes are synchronized with and caused by changes in solar radiation rather than changes in atmospheric composition.
-The truth about global warming - it’s the Sun that’s to blame