The emergence of climate change as a pivotal global issue has brought with it an array of assumptions and predictions, many of which evoke fear and guilt.
In my opinion, there is no conclusive proof that human emissions of carbon dioxide (CO2) are the dominant cause of the minor warming of the Earth’s atmosphere over the past 100 years. If there were such a proof it would be written down for all to see. No actual proof, as it is understood in science, exists.
The UN’s Intergovernmental Panel on Climate Change (IPCC) states: “It is extremely likely that human influence has been the dominant cause of the observed warming since the mid-20th century.”
“Extremely likely” is not a scientific term but rather a judgment. The IPCC defines “extremely likely” as a “95-100% probability”. But upon further examination it is clear that these numbers are not the result of any mathematical calculation or statistical analysis.
These judgments are based, almost entirely, on the results of sophisticated computer models designed to predict the future of global climate. A computer model is not a crystal ball.
Perhaps the simplest way to expose the fallacy of “extreme certainty” is to look at the historical record. When modern life evolved over 500 million years ago, CO2 was more than 10 times higher than today, yet life flourished at that time. Then an Ice Age occurred 450 million years ago when CO2 was still about 10 times higher than today. There is some correlation, but little evidence, to support a direct causal relationship between CO2 and global temperature through the millennia. The fact that there were both higher temperatures and an ice age at a time when CO2 emissions were 10 times higher than they are today fundamentally contradicts the certainty that human-caused CO2 emissions are the primary cause of climate change.
Today’s average global temperature is 14.5oC. This compares with a low of about 12oC during the periods of maximum glaciation in this Ice Age, to an average of 22oC during the Greenhouse Ages, one of which occurred prior to the most recent Ice Age. During the Greenhouse Ages, there was no ice on either pole and all the land was tropical and sub-tropical. As recently as 3 million years ago the Canadian Arctic islands were forested. Today, we live in an unusually cold period and there is no reason to believe that a warmer climate would be detrimental for humans and the majority of other species. There is reason to believe that a sharp cooling of the climate would be disastrous for human civilization.
The IPCC states that humans have been the dominant cause of warming “since the mid-20th century”. From 1910 to 1940 there was an increase in global average temperature of 0.5oC. There was then a 30-year “pause” until 1970, followed by an increase of 0.57oC during the 30-year period from 1970 to 2000. Since then there has been no increase in average global temperature. This in itself tends to negate the validity of the computer models, as CO2 emissions have continued to accelerate during this time.
The increase in temperature between 1910 and 1940 was virtually identical to the increase between 1970 and 2000. Yet the IPCC does not attribute the increase from 1910-1940 to “human influence.” They are clear in their belief that human emissions impact only the increase “since the mid-20th century”.
It is important to recognize, in the face of dire predictions about a 2oC rise in global average temperature, that humans are a tropical species. We evolved at the equator in a climate where freezing weather did not exist. The only reasons we can survive these cold climates are fire, clothing, and housing. It could be said that frost and ice are the enemies of life, except for those relatively few species that have evolved to adapt to freezing temperatures. It is “extremely likely” that a warmer temperature than today’s would be far better than a cooler one.
If we wish to preserve natural biodiversity, wildlife, and human well-being, we should simultaneously plan for both warming and cooling, recognizing that cooling would be the most damaging of the two trends. We do not know whether the present pause in temperature will remain for some time, or whether it will go up or down in the near future. What we do know with “extreme certainty” is that the climate is always changing, between pauses, and that we are not capable, with our limited knowledge, of predicting which way it will go next.