Addressing Global Warming Claims

Unless you are a new arrival from another planet, you have probably heard or read at least one of the following claims (among other possibilities):

  1. Global warming is occurring—or, conversely, is not occurring. (Presidential candidate Ted Cruz has, for example, referred to global warming believers as “alarmists,” and has “compared people who think that the climate is warming to ‘flat-Earthers’ and described himself as a modern-day Galileo in an interview with the Texas Tribune.”)
  1. Global warming is occurring, and is human-caused (i.e., anthropogenic)—by our burning of fossil fuels and our deforestation activities especially.
  1. The unusual weather that we have been experiencing during the past few years (e.g., the recent spate of tornadoes, and the flooding) is a consequence of the global warming that is occurring.
  1. Not only is global warming occurring, but is likely to render our species extinct within a matter of decades, if not years.

If you are anything like me (“I’m a “doubting Thompson”!), when you learn of unusual claims—even ones stated by “experts”—your reaction is: “Provide me with enough solid evidence to convince me that I should accept your claim.” I, in learning of the above claims, have tried to seek out evidence relevant to each one, and I use this essay to report on what I’ve found. In some cases the evidence is rather substantial, so that one can say with confidence that the claim either has, or lacks, a sound basis.

The last of the four claims listed above, however, probably cannot be given a definitive “answer”: Whereas the first three claims refer to the present, the last one references the future; in referring to the “not yet,” only reasoned (and “wild”!) guesses are possible, some more plausible than others. Because of the fact that the first three, of the above four claims, have a time reference that the fourth one lacks, below I discuss the first three claims together in the same section, and discuss the fourth one in a separate section that then follows.

Because the subject of “greenhouse” gases inevitably enters any discussion of global warming, I begin here with a section that briefly discusses those gases and their role. Before doing so, however, I should note that “global warming” is also referred to as “climate change” (among other possibilities); and that although I prefer the term “climate disintegration” (for reasons stated later) for this phenomenon, herein I will use the term “global warming.”

Greenhouse” Gases

A layer of “greenhouse” gases (such as carbon dioxide, CO2, water vapor, and nitrous oxide) surrounds the earth, and the presence of such gases is an enabler of human life. As the short-wave energy from the sun that reaches our planet strikes earth, that energy is either absorbed by the earth or it “bounces off.” The reflective tendencies of a given surface are referred to as its albedo, this being expressed on a scale from 0 to 1.0. A surface of fresh snow, for example, tends to reflect most of the sun’s rays that strike it, and therefore has a “high” albedo (a value of about 0.9.

Short-wave rays from the sun that strike dark surfaces tend to be absorbed, and to heat that area to a certain depth. That area, in turn, then re-radiates long-wave heat energy into the atmosphere, and it is the presence of greenhouse gases in the atmosphere that prevents that energy from simply escaping into the deep atmosphere. In a sense, those gases “trap” heat energy, much like the glass of a greenhouse does—which is why those gases are termed greenhouse gases. Another way of expressing this point is that the layer of greenhouse gases acts as a sort of “blanket.”

More will be said about these gases as the essay progresses, but my purpose in this brief section was simply to clarify, briefly, what they are and what they do. Let us next, then, turn to the first three of the claims stated above.

The First Three Claims

Is Global warming Occurring?

The graph below shows temperature variation—for the earth as a whole—during the past 1,000 years (source):

The red line shows temperature variation; and although the blue line depicts CO2 variation over that period of time, if we were to create a trend line for temperature, it would correspond rather closely to the CO2 line! Later I will comment on that matter.

Note that the temperature values depicted on this graph are not absolute values but, rather, are relative ones—relative to the temperatures of the 1956-1995 time period. Although the Y (temperature) axis of the graph contains no zero, if we were to draw a horizontal line on the graph at the 0 position, we would see that for much of the time during the past 1,000 years, although temperatures varied considerably, even at their warmest they were below the graph’s “normal.” Also note, however, that since about 1850 the trend has been upward; there has been variation from year to year, certainly, but it’s clear that the trend has been upward.

The first person to actually take temperature data and then determine whether or not global warming was occurring was Guy Stewart Callendar [1898-1964]:

In 1938, Callendar compiled measurements of temperatures from the 19th century on, and correlated these measurements with old measurements of atmospheric CO2 concentrations… He concluded that over the previous fifty years the global land temperatures had increased, and proposed that this increase could be explained as an effect of the increase in carbon dioxide.

(I should add here that before Callendar’s research, Svante Arrhenius [1859-1927] had done some important work:

Arrhenius developed a theory to explain the ice ages, and in 1896 he was the first scientist to attempt to calculate how changes in the levels of carbon dioxide in the atmosphere could alter the surface temperature through the greenhouse effect

Based on information from his colleague Arvid Högbom (sv), Arrhenius was the first person to predict that emissions of carbon dioxide from the burning of fossil fuels and other combustion processes were large enough to cause global warming.)

The fact that earth’s temperature increased by 0.85° C between 1880 and 2012 is further proof, of course, that global warming is occurring—i.e., that there is a trend of global warming. Thus, the claim that global warming is occurring has been rather well established.

Is Global Warming Anthropogenic (i.e., human-caused)?

GW2_DVIt’s been claimed that the global warming now occurring is of an anthropogenic nature—i.e., caused by the burning of fossil fuels and by deforestation activities. A reason for doubting this claim is implicit in this graph (source). It shows CO2 variation over the past 800,000 years. For most of that period there was important variation in CO2 level; and insofar as there was trend, it was one of little change. (However, since 1850, the trend has been one of increase, as I noted above.) Now given that anatomically modern humans have been in existence for only the past 200,000 years, of the past 800,000 years, it’s obvious that for most of the past 800,000 years, it is non-human factors that have affected CO2 levels. That fact gives one at least some reason to doubt the claim that the warming that is occurring at present is human-caused.

However, the fact that the CO2 line on the first graph depicted above is, simultaneously, a virtual trend line for temperature (as I noted earlier), combined with the fact that CO2 emissions are known to produce warming (as Arrhenius determined over a century ago), gives us a rather sound basis for accepting the thesis that the global warming that has been occurring does have a human cause. A question that arises here (and given some attention later), however, is whether or not non-human factors could come to the fore that would change the relationship that now exists between CO2 level and temperature.

Is Our Unusual Weather a Result of the Global Warming That’s Occurring?

I suspect that the term “global warming” goes back to Callendar’s research, because he limited his focus to temperature. However, since Callendar’s time researchers have come to realize that the heat energy being added to the atmosphere via an increased “greenhouse effect” (i.e., increased concentration of greenhouse gases) is causing not only a trend in increased global temperature, but (a) an increase in the number of storms, (b) an increase in their size and severity, and (c) an increase in weather variability (directly resulting from changes in the course of the jet stream, e.g., those changes caused by the added heat energy).

Thus, it is possible to say that the unusual weather that we have been experiencing is consistent with global warming, but that does not constitute proof that global warming is the cause of the unusual weather now occurring.

Will Global Warming Render Our Species Extinct “Soon”?

This question is inherently more difficult to grapple with, first, because it involves a projection into the future, and the future cannot be known with certainty. It is tempting for scientists to assume that the factors now acting (a) will continue to act, and that (b) no additional factors will enter the picture. The graph above that depicts CO2 variation over the past 800,000 years shows that during most of that period the level of concentration ranged from a low of about 175 ppm to a high of about 300 ppm.

Given that for most of that period, when it increased, it did so in response to “natural” factors, and the same for those periods when it decreased, this question arises: Is it not at least conceivable that some of the factors long before humans were present will enter the picture again, doing so in such a way as prevent earth from being rendered uninhabitable (with our species then becoming extinct)? If we knew why the level of CO2 in the atmosphere declined fairly steadily from a 300 ppm level to a 175 ppm level, is it not possible that geo-engineering measures could be developed that could replicate the earlier natural process?

Not myself being a scientist, I have no idea what the answers to those two questions might be. Nor do I know if it’s even meaningful to ask those questions. I pose them here, however, in the event that they might have some merit.

Not only is the question of whether global warming will render our species extinct one that is inherently difficult to grapple with because of its future orientation; unlike the other three questions, this one requires the presentation of an argument: A series of statements that are logically connected. This fact presents us with two problems: (a) Unless the statements constituting the argument have a solid basis, the conclusion “produced” by the statements will not be one that one can accept; (b) if the argument omits statements regarding factors that are, or will be, playing a role in affecting the conclusion, again the conclusion will be unacceptable. This second point has, however, the problem that one is likely to unaware of what one has omitted!

Because of these problems, I am not as sanguine as some are about our “inevitable” demise as a species within a few decades, or even years. I would like to think that my attitude here is not so much influenced by the fact that my wife and I have three children and five grandchildren (so far) but, rather by the “facts.” However, I am quick to add that as I now perceive the facts of which I am aware, I see little reason to believe that we humans will be able to escape near-term extinction. After all, we are now living in the period of the “sixth extinction,” so what makes us think that we are so “special” that we won’t be among those species now becoming extinct?!

Here is why I see little reason for hope, stated as a series of points:

1. The parts per million (ppm) level of CO2 that was in our atmosphere prior to the beginning of the Industrial Revolution—about 280 ppm—can be regarded as an appropriate level for human existence.

2. “The daily average concentration of atmospheric CO2 at Mauna Loa first exceeded 400 ppm on 10 May 2013.” There is every reason to believe that further increases in the ppm level will be forthcoming.

3. This increase has meant an increase in heat energy in the atmosphere, resulting in (a) a heating trend (about 0.85° C. since the beginning of the Industrial Revolution), (b) an increase in the number of storms, (c) an increase in their size and severity, and (d) increased variability in weather phenomena at any given location (the degree of that variability varying from place to place, of course). Presumably, these phenomena will intensify with a continuation of global warming.

4. Even with a cessation—tomorrow—in the burning of fossil fuels and deforestation activities, the atmospheric phenomena under point (3) above would continue, because the greenhouse gases would continue to be in the atmosphere, with the ppm level decreasing only gradually over time. One source states this: “Individual carbon dioxide molecules have a short life time of around 5 years in the atmosphere. However, when they leave the atmosphere, they’re simply swapping places with carbon dioxide in the ocean. The final amount of extra CO2 that remains in the atmosphere stays there on a time scale of centuries.” One site states that it would take even longer: “What would happen to the climate if we were to stop emitting carbon dioxide today, right now? Would we return to the climate of our elders? The simple answer is no. Once we release the carbon dioxide stored in the fossil fuels we burn, it accumulates in and moves amongst the atmosphere, the oceans, the land, and the plants and animals of the biosphere. The released carbon dioxide will remain in the atmosphere for thousands of years.”

5. As heating in particular increases, it’s likely that a point in time will be reached such that after that point (“tipping point”) the phenomena listed in point (3) above will begin to accelerate. The reason: Global warming is a process that tends to “feed upon itself.” That is, the initial effects of specifically warming cause changes (e.g., the melting of snow and ice) which result in further increases in temperature: (a) Less of the short-wave energy coming from the sun will be reflected back into space; (b) the amount of exposed bare ground will increase, it will absorb more short-wave heat energy, and therefore re-radiate more long-wave heat energy, producing heating; (c) the thawing of permafrost will release methane gas, a greenhouse gas far more potent than CO2 in “contributing” to more warming; (d) etc.

6. GW3_DVThe fact that global warming is a process that “feeds on itself” suggests that the global mean could at least reach an Eocene level. The graph below indicates that over the past 65 million years, temperatures were highest during the Eocene (source). (Note that on this graph the present is shown on the left, rather than right, side! Also, here’s a definition of “benthic.”) Presumably, human life could not exist in Eocene conditions.

7. Recognizing the above facts, it is important to cease those activities that will contribute to heating “long” before the tipping point is reached, because specifically of points (3) and (4).

8. It’s likely, however, that we have already passed that point; in fact, in 2013 Arctic climate scientist John B. Davies stated: “The world is probably at the start of a runaway Greenhouse Event which will end most human life on Earth before 2040.”

9. There are no signs that our leaders are taking global warming seriously—making Davies’s projection highly plausible. That is, even if we have not yet reached the tipping point, point (5) suggests that it’s likely that we will in the near future.

10. If it were possible, using geo-engineering measures, to prevent our near-term extinction (by, e.g., removing greenhouse gases from the atmosphere, reducing the amount of insolation reaching the Earth, etc.), we could “rest easy.” However:

  1. There’s no reason to believe that such measures will be developed.
  1. If they are, there is no reason to believe that they will be implemented.
  1. If such measures are implemented, there’s no reason to believe that they will “work”—with the possibility, even, that they will bring the time of our extinction even closer (than, e.g., 2040!). In fact, Guy McPherson is on record of declaring that our species will be extinct by 2030! Because any use of geo-engineering measures would be of an “experimental” nature, many scientists have expressed their opposition to such measures—and last year politician Al Gore declared the use of such measures as “insane”!


What we do know about global warming suggests that because global warming is a process that “feeds on itself,” unless its causes are removed long before a “tipping point” is reached, “runaway” may begin at some point, and it will be impossible to halt the process. The reason it’s essential to remove the causes far in advance of the arrival of the “tipping point,” is that the greenhouse gases that are directly responsible for global warming will remain in the atmosphere for centuries, perhaps much longer; and although their degree of presence in the atmosphere will diminish over time, while they are still present, they will contribute to continued heating.

It’s conceivable that certain geo-engineering measures could be developed that, because they emulated Nature’s past control of the CO2 presence, could be trusted “safely” to reduce the level of greenhouse gas concentration enough—and quickly enough—to prevent our extinction. However, given the points listed under point (9) above, it’s virtually impossible to believe that this will occur—and that if such measures are developed, they will be implemented, and in time.

I hate to end an essay on such a depressing note, and would therefore direct the reader to my “Explanations: Useless and Otherwise,” written about 6 months ago, for some ideas of a far more positive nature.

Al Thompson retired four years ago from an engineering (avionics) firm in Milwaukee. His e-mail address is: Read other articles by Alton.