Geological science has long established that changes in the Earth’s temperature are not unique to our present.
Indeed, the temperature of the Earth has varied quite significantly over the long course of Earth’s history. The Earth has been cold enough to form ice sheets extending to the equator and it has also been warm enough for palm trees to grow on the Antarctic continent and warmer still. So, change in the Earth’s average temperature in itself is normal. However, the causation of the current warming is unique and the rapidity of the current warming poses the gravest threats to civilization and possibly the survival of our species.
Is the recorded recent warming just “cyclical” variability of “mother nature”? In 1975 climatologists concluded that the Earth was not cooling as was expected from the natural Milankovitch cycles, that have explained the instigation, i.e. initial temperature change, leading to the ice ages and interglacial periods (from 355-280, and 33 million years ago to the present). After cooling was ruled out climatologists proceeded to research the possibility of global warming - after an approximately 10,000 year period of minimal temperature variation around 57 degrees Fahrenheit and the rise of large scale cities “creating” civilization as we know it.
The uniqueness of our current period of global warming (as opposed to the natural global warming in interglacial periods instigated by the Milankovitch cycles) relies upon an understanding of the role of a planetary atmosphere and the particular composition of a planetary atmosphere, specifically the increase in our atmosphere of gases that absorb/retain radiant heat. The common source of heat energy for our entire solar system is solar radiation. However, why is it that at this point in time the average surface temperature of Mercury, receiving the greatest amount of solar energy, is 332 degrees Fahrenheit while the average temperature of Venus is 854! degrees Fahrenheit? The answer lies primarily in the ability of the Venusian planetary atmospheres to retain heat. While Mercury receives the greatest amount of solar radiation it lacks its own atmosphere that might retain more solar energy, Venus receives less radiant solar energy than Mercury but has an extremely dense atmosphere which is comprised 95+% of carbon dioxide (CO2) atoms which absorb and retain some of the solar radiation heat energy in the atmosphere. Until this contemporary relatively rapid warming period on Earth began, the temperature of the Earth (with a comparatively thin atmosphere compared to Venus and made up of 99% nitrogen and oxygen which are not warming gases and trace gases including CO2) was 57 degrees Fahrenheit as compared to 14 degrees Fahrenheit without an atmosphere.
After a “long summer” of about 10,000 years of a stable average Earth (near) surface temperature of about 57 degrees Fahrenheit, the Earth has been warming since the Industrial Revolution began in the 18th century by, approaching, 1 degree Centigrade (1.8 degrees Fahrenheit), increasingly rapidly after 1950 and even more rapidly after 1980. In 1988, Dr. James Hansen, the Director of the NASA Goddard Institute for Space Studies, testified before the Senate Energy and Natural Resources Committee that he was 99% certain that the Earth was warming beyond natural variation because of an increase in atmospheric warming gases as a result of human activity. In the same year the Intergovernmental Panel on Climate Change (IPCC) was formed and in 1990 it confirmed the warming trend and that emissions from human activities were partly responsible for the warming by increasing emissions of greenhouse, i.e. warming, gases into the atmosphere which, in turn, increased water vapor, the most abundant and powerful warming gas, in the atmosphere. By the 2001 report of the IPCC, stronger evidence had accumulated that most of the warming was attributable to human activity. In particular, in 1995 researchers led by Dr. Benjamin Santer found that the vertical structure of the atmosphere was graphically different from the structure produced by natural warming. Also, in 1997, Dr. David Easterling found that nighttime low temperature were rising twice as fast as daytime highs consistent with human induced warming as opposed to natural variation (Note, by 2012, record highs were 9 times record lows compared to the 50/50 pre-1950 1950 distribution). In 1998, Dr. Michael Mann concluded that scientists found that during the 20th century the effects of CO2 emissions swamped natural factors. By the 5th report in 2014, the IPCC found with a 95% level of confidence, i.e. comparable to the confidence level in the relationship between smoking tobacco and lung cancer, that warming due to human activity swamped natural temperature variation.
Today, the basic fact of global warming is unequivocal settled science in the world scientific community. Similarly, it is settled science that the most important factor driving the warming is human activity, primarily the burning of fossil fuels, i.e. coal, oil, and natural gas, to generate energy. The burning of fossil fuel has first and foremost changed the nature of our atmosphere by raising the level of CO2 in our atmosphere from 280 per million molecules to 400 per million. In addition to burning fossil fuels and agricultural activity, human activity has and is also promoting global warming by substantially reducing forests (which absorb CO2) as well as by increasing the amount of other heat trapping gases, e.g. methane, nitrous oxide, CFCs and HFCs, in the atmosphere. As a result of this changing atmospheric composition, average Earth temperature is steadily increasing resulting in continuous “climate change” and a host of consequences that are causing increased property loss, injury, disease and death as well as many other negative changes in human communities and ecological systems generally throughout the world.