Is Global Warming Due Mostly to Human Activities?

An article “Environmental Problems: Global Disasters Waiting to Happen” in the June 2018 release of this website discusses evidence that global warming (or climate change) is definitely occurring. The increase in the world’s average temperature will have tremendous impacts on the livelihood of essentially all localities across the globe.  If we don’t take appropriate actions now, these problems are serious and could become insurmountable 50, 100 years from now. These insurmountable problems will be faced by our children, grandchildren, and great grandchildren due to the actions or in-actions that our leaders adopt today. impacts such as:

  • More drought and flooding across the whole globe
  • Less ice and snow resulting in insufficient water for areas that depend on melting ice and snow from mountains
  • More extreme weather incidents resulting in more deadly heat waves, violent rainfalls, and severe storms
  • Rising sea level, resulting in massive flooding along every coast.

The 2015 Paris Climate Agreement is a symbol of hope that the leaders of the world are wise enough to recognize the problem and start to initiate actions to address the problem. [1]  Unfortunately, our current president of the U.S., Donald Trump, has already announced that the U.S. will withdraw from the Paris Climate Agreement.

The next critical question is whether global warming is due mostly to human activities.  In other words, if global warming is due mostly to natural phenomena or is a historical trend of our planetary system, then there may not be much we as humans can do about it.  This article discusses evidence from scientific analysis that global warming during the last 100+ years is primarily due to human activities.

What is global warming?  The sun radiates a lot of sunlight (in the visible wavelength) toward earth.  Part of the sunlight is reflected back to space, and part of the sunlight is absorbed by the atmosphere, and part of the sunlight passes through the atmosphere unchanged (i.e., transparently). When the sunlight hits the surface of the earth, it interacts with the surface of the earth, part of that energy is transferred to the molecules of the surface of the earth by increasing their molecular motion.  The earth’s surface then re-rediates that energy as heat (in the infrared wavelength) to the atmosphere.  Some of that heat energy is absorbed by the earth’s atmosphere, and the rest is radiated back to space.  The amount of the heat energy absorbed by the earth’s atmosphere depends on the types and amounts of material in the atmosphere.  That energy trapped by the atmosphere can warm up the atmosphere and the surface of the earth.  If we increase the amount of certain matter in the atmosphere, then the amount of energy absorbed by the atmosphere increases, thus increasing the temperature in the atmosphere and around the surface of the earth, including the water in the ocean.

This is like sunlight entering a greenhouse, and part of the reflected sunlight gets trapped by the glass of the greenhouse and increases the temperature in the greenhouse.  That is why global warming is also known as the greenhouse effect. because part of the energy re-radiated by the earth is absorbed by the earth’s atmosphere resulting in an increase in the temperature of the atmosphere and the surface of the earth.

History and Current Status of Global Warming Research:  Actually global warming research is not new.  It goes back to 1859 when the Irish physicist John Tyndall found that carbon dioxide absorbed heat and so variation in the composition of the atmosphere could create changes in climate. Using Tyndall’s findings, the Swedish chemist and future Nobel laureate Svante Arrhenius pointed out in 1896 that the combustion of coal and petroleum could raise global temperatures.  Numerous scientific research in the last 100 years have confirmed that the increasing amount of carbon dioxide in our atmosphere from burning coal, gas, and petroleum does contribute to global warming.  Scientists can correlate the increase of carbon dioxide and therefore its contribution to global warming in the last 150 years.  Besides carbon dioxide, our atmosphere contains other gases, such as water vapor, methane, nitrous oxide, ozone, chlorofluorocarbons, and hydrofluorocarbons.  Similarly, scientists can estimate the contribution to global warming (or sometime global cooling) from other influencers in the last 150 years.  Such research has repeatedly shown that over this extended period the contribution from carbon dioxide matches nicely with the increase in the earth’s surface temperature over the last 150 years.

There are other natural (i.e., not man-made) influencers that may contribute to global warming.  Here are the two most common examples of natural influencers:

  • Do changes to solar radiation contribute to global warming?  It is true that over long periods (millions of years), changes in solar radiation has contributed to earth’s climate change, e.g., ice ages.  However, all the research studies have shown that changes in the rate of solar heating over the last century cannot account for the magnitude of the rise in global mean temperature over this extended period.
  • Are volcano eruptions causing global warming?  Just the opposite, volcano eruptions inject sulphate aerosols high into the stratosphere, where they can remain aloft for a few years, but the sulphate aerosols will reflect incoming sunlight back into space, thus cooling the earth’s surface.  Furthermore, once the sulphates drift back down to the surface of the earth, the cooling effect of volcanoes goes away.  Both of these results are inconsistent with the observed data.

As a matter of fact, the contribution to global warming from carbon dioxide alone would have increased the earth’s temperature even more than the observed curve.  After taking into account that certain influencers actually decrease the earth’s temperature, such as volcano eruptions or man-made aerosol released into the atmosphere by various aerosol cans (e.g., for mosquito repellents), then the total contribution to global warming matches nicely with the observed increased in temperature over the last 150 years. [2]

Political History and Implications:  Actually fairly early top scientists and leaders of the U.S. government already realized the seriousness of the global warming problem.  For example, in 1974, the CIA already issued a classified report that climate change had begun around 1960 due to the carbon dioxide problem, and had “already caused major economic problems throughout the world.”  In 1978, Jason, the federal government’s premiere team of the most intelligent American scientists already issued a report that when the amount of carbon dioxide doubles in about 50+ years, disastrous climate changes would result, including rapid melting of the West Antarctic ice sheet.  In 1979, Dr. Jule Charney, the father of modern meteorology and a team of the nation’s top oceanographers, atmospheric scientists and climate modelers issued a report validating the seriousness of the global warming problem.  This study was commissioned by Dr. Frank Press, Scientific Advisor to President Carter.  In other words, almost 40 years ago, the scientific results were already fairly extensive and definitive that the overwhelming majority of climate scientists believe strongly that global warming is both a fact and is caused by human activities.

However, for various political reasons and the lobbying strength of the coal, gas, and oil industry. the necessary actions that can address and slow down the global warming problem were never implemented during the last almost 40 years.  We know that if we don’t act to reduce emissions of carbon dioxide, the problem may escalate to a point of no return.  The problem will be worse for our children, and become more worse for their children, and their children’s children.  It seems that based on our inactions, their lives don’t seem to mean anything to us.  We hope that at some point, the fears of our young people, will overcome the fears of the old, and a future generation will gather enough wisdom and power to act. [3]


[1]  The 2015 Paris Climate Agreement is a voluntary agreement, and almost all the countries of the world are not doing nearly as much as what were projected.  Nevertheless, its very existence is a recognition by the international community of the importance of this issue and the need to address it.

[2] See, e.g., the article “Analysis: Why scientists think 100% of global warming is due to humans“:  https://www.carbonbrief.org/analysis-why-scientists-think-100-of-global-warming-is-due-to-humans.

[3] The whole 60-page August 5, 2018 issue of the New York Times Magazine was about the global warming problem.

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2 Responses to “Is Global Warming Due Mostly to Human Activities?”

  1. Pamela Blunt says:

    Thank you, Don. Very well written. I agree 100%. Nice to have things laid out so well for when someone asks about global warming.

  2. Paul L Chang says:

    Agree with your viewpoint. There are supernatural forces, however, there are also human factors.
    But let it not be handled as tool for political gains. Citizens should have correct education in this regard.
    Taiwan is a worst example. If no correction in the very near future, the so-called Formosa will lose her beauty due to PM 2.5 corruption.

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