The subject of global warming has evoked differing opinions among scientists and citizens on the proposition that human activity is causing dangerous warming of planet earth. It is said by proponents of that proposition that the science is settled, and that there is a consensus of scientists in favor of the proposition.
Contrary to the assertion that the science is settled on this issue, there are numerous scientists who differ with the proposition. See, for example, the publications of the Nongovernmental International Panel on Climate Change (NIPCC) listed at http://climatechangereconsidered.org/
The lead authors and editors of a recent publication of NIPCC include forty-seven climate scientists. In 2015 the NIPCC published a book entitled Why Scientists Disagree About Global Warming. The book explains why there is no merit to the claim of scientific consensus on the causes and consequences of climate change. The authors rebut the surveys and studies used to support claims of a consensus. They then summarize evidence showing disagreement, identify four reasons why scientists disagree about global warming, and then provide a detailed survey of the physical science of global warming based on the authors’ previous work.
A “Global Warming Petition to Congress” was signed by 31,487 scientists, including 9,029 with Ph.Ds. The Petition begins with the following statement:
“We urge the United States Government to reject the global warming agreement that was written in Kyoto, Japan in December 1997, and any other similar proposals. The proposed limits on greenhouse gases would harm the environment, hinder the advance of science and technology, and damage the health and welfare of mankind.
“There is no convincing scientific evidence that human release of carbon dioxide, methane, or other greenhouse gases is causing or will, in the foreseeable future, cause catastrophic heating of the Earth’s atmosphere and disruption of the earth’s climate. Moreover, there is substantial scientific evidence that increases in atmospheric carbon dioxide produce many beneficial effects upon the natural plant and animal environments of the earth.” See http://www.petitionproject.org/
How can one evaluate these conflicting assertions? Very few people are in a position to check personally on the accuracy of data advanced by scientists on any aspect of the debate. Almost no one can independently measure global temperature changes, sea level rise, melting of ice in glaciers or at the North Pole or in Antarctica, etc. Even if one could check on these things for oneself, given that there are so many conflicting explanations of the phenomena, how could one know what conclusions to draw?
A comment of famed and garrulous baseball manager Casey Stengel could be helpful in this regard. He was fond of saying “you could look it up” to back up his phenomenal memory. This brief essay posits that there are some important facts about climate that an individual could look up to shed some light on this contentious issue.
Just a little knowledge of the geological, biological and anthropological history of planet earth would lead one to wonder about the idea that earth and its inhabitants are in danger from global warming caused by human activities. For example, the following are facts anybody could look up and that nobody disputes. Discovery of these facts is due to the continual accretion of knowledge in the physical and biological sciences.
- Earth is 4.57 billion years old
- There have been three different climates over this 4.57 billion year period:
The earliest when the climate was extremely hot and the planet was molten and volcanic, without life of any kind
The second when the planet cooled, water collected in the oceans and on land, and bacteria and early life forms appeared
The third, starting about 540 million years ago when the current climate of the earth developed and life as we know it now emerged
- There have been four ice ages affecting earth in the past three billion years. Within ice ages, there have been periods of more severe glacial conditions and more temperate conditions, known as glacial periods and interglacial periods; in interglacial periods earth warms up but is still in an ice age.
- Currently, earth is in a period of interglacial warmth in the Pleistocene ice age, which is the most recent ice age. The current interglacial warming period started about 11,700 years ago. It is during this warming period that human civilization evolved to what we know today.
- During interglacial periods, glaciers retreat. That has been happening since the end of the last period of glaciation 11,700 years ago. The current geological warming epoch is called the Holocene Epoch. It continues up to the present.
- Since the beginning of the Holocene warming, about 11,700 years ago, the human population of the earth has grown from less than 15 million to around 7 billion.
- During the last 12,000 years there have been alternating periods of cooling and warming over periods ranging from thousands of years to decades.
- During a period known as the Holocene maximum, from about 9,000 years ago to about 5,000 years ago, temperatures on earth were warmer than at present. Another warming period known as the medieval warming occurred from about 1,000 C.E. to 1,400 C.E. During the medieval warming, temperatures were warmer than at present.
- The medieval warming was followed by a cooling period known as the Little Ice Age that lasted from approximately the 14th century to around 1850.
- Since 1880 the average global temperature has risen by around 0.8 degrees Celsius, or about 1.4 degrees Fahrenheit.
- Within this recent warming trend there was a period of cooling, from 1940 to 1976.
- Earth warmed again from 1976 to 1998. In 1998 there was an El Niño warming event. The term El Niño refers to periodic warming in the ocean in tropical latitudes of the central and eastern Pacific Ocean.
- Since 1998 average global temperatures have neither warmed nor cooled to any significant degree.
- Carbon dioxide is not a pollutant, and not a harmful substance; it is plant food. Like water, energy from the sun, and the atmosphere, carbon dioxide is essential to life on earth. Every living thing on earth contains carbon.
We could write much more about this but will conclude these remarks by considering one phenomenon that is supposed to be circumstantial evidence of the danger of global warming to human beings and animals. That is the polar bears. According to Al Gore’s film An Inconvenient Truth (2006), polar bears face extinction due to melting of ice in the arctic. However, the polar bear population has actually increased from 5,000 to 25,000 in recent decades. The biggest threat to polar bears is human hunting of the bears. This subject is examined in detail in the book Cool It: The Skeptical Environmentalist’s Guide to Global Warming (2007) by Bjorn Lomborg.
[NOTE: In an Appendix to the Education chapter of the book portion of this website, under the title CRITICAL ANALYSIS AND THE SCIENTIFIC METHOD, there is a more detailed essay on the science involved in appraising the hypothesis that human activity is causing dangerous global warming.]