“It remains unfortunate that the opinions of a handful of contrarians should be given the same weight in the press and the popular media as the studied conclusions of thousands of scientists.” —Astrophysicist Richard D. Schwartz

Back in 2012, the current occupant of the Oval Office, who is known for hyperbole, declared, “The concept of global warming was created by and for the Chinese in order to make U.S. manufacturing non-competitive.” And Trump knows, because “the hottest day ever was in 1890-something, 98.”  Trump also insisted that he has “a totally open mind.”

With the hacking of emails between scientists reportedly providing evidence that global warming and climate change is a hoax, it is important to understand at a minimum the rudimentary physics of the earth’s climate.  NASA and NOAA data indicate that, with 95 percent confidence, 2016 was the warmest year since 1880, when modern recordkeeping began, and, contrary to Trump’s assertion, the warmest periods have occurred over the last 35 years.  Presently, global mean temperature is 1° C (about 2° F) above the mid-twentieth century mean value.

Since recorded temperatures only go back to 1880, we should ask, how can scientists presume to discuss temperatures from 100,000 years ago or even 1,000?  It turns out there are several indirect methods of determining temperatures, such as examining ice cores, coral reefs and tree rings, and while not all the data are consistent, in most cases the inconsistencies can be resolved.  And the sheer volume of data from diverse sources corroborating the global temperature rise is hard to refute.  Nevertheless, some intelligent individuals remain stubbornly skeptical.

Looking back over the millennia, scientists have been able to see a pattern to the relative warm and cold periods on this fragile planet known as earth.  The period between successive peaks and valleys in global temperature is a rather consistent 100,000 years.  Over that period of time, the earth’s elliptical orbit around the sun oscillates between greater and lesser eccentricity. That is to say, the orbit becomes more like a circle at times and is more elliptical at others. 

As a result of these orbital fluctuations, which are caused by the gravitational influence of the planets Saturn and Jupiter, the earth is closer to the sun when the orbit is more elliptical and has a relatively warm period, while our planet is colder when the orbit becomes more circular.  The effect isn’t much of a change; there is only about a 3.4 percent variation in distance between the earth and the sun.  While this phenomenon is the primary driver of the earth’s normal climatic cycles, there are other mechanisms at work amplifying or negating the normal temperature trend.

Now here is the first worrying surprise.  Based on these long term temperature cycles, which are known as Milankovitch cycles after the Serbian scientist, Milutin Milankovitch, who first reported them, we are on the downward slope heading towards another ice age, and temperature records over the last thousand years confirm this.  The problem is that since 1900, scientists have noticed a persistent temperature increase going against the 450,000-year historical pattern. Likewise there is solid data indicating the carbon dioxide levels (CO2) since 1900 have increased dramatically as well. 

Scientists know that the water molecule, H2O, is the most important component in the earth’s delicate temperature balancing act, so how could CO2 be such an important factor in this counter-cyclical warming trend?  The simple answer is that the most abundant atmospheric gases, nitrogen and oxygen, do not absorb infrared (heat) rays, leaving only CO2 and a few other infrared-absorbing gases like methane (CH4) and ozone (O3) as the probable suspects in the recent sudden temperature rise. And copious amounts of CO2—currently around 22 billion tons each year—have been generated by mankind.

Historically, CO2 levels in the atmosphere have risen along with temperature levels, but there is another awaiting surprise: if we plot both on a time scale, we note that there is roughly an 800-year lag in CO2 buildup from the onset of higher mean temperatures.  Some skeptics have used this fact to dispute the premise that the currently observed higher levels of atmospheric CO2, mainly produced from carbon-based energy sources, is causing an increase in mean global temperature.  This lag, in their contrarian view, shows that the anthropogenic global warming (AGW) theory is false.

However, the temperature rise scientists have seen in the post-1900 data is anomalous.  Based on the Milankovitch cycles as previously noted, the global temperature trend should be going down, not up.  Given that levels of atmospheric CO2 are steadily increasing, it appears to be the culprit. The physics of the CO2 molecule are well known, the so-called “greenhouse effect,” in which CO2 absorbs infrared (heat), becomes excited and transfers kinetic energy through collisions with adjacent molecules.  The average kinetic energy of the gas molecules is a measure of heat.

There is one more issue of grave concern to be considered.  The ocean indeed absorbs CO2 and acts as a “carbon” sink. In waters close to the surface, CO2 is absorbed rather quickly but the depths absorb it at a much slower rate, and it is the ocean depths that form the largest sink with ten times the capacity of all the others combined.  Atmospheric CO2 is transferred to shallow ocean waters rather quickly, reaching equilibrium in 10 to 20 years.

However, transfer to the ocean depths is much slower; the CO2 being dumped into our atmosphere today will not be absorbed in deep water for another hundred years.  So even if use of carbon-based energy were to be terminated tomorrow, the beneficial effects (if any, according to skeptics) would not be realized until the 22nd century.  So to act based upon available evidence of AGW is an economic non sequitur to corporate capitalism, with its emphasis on short term profit maximization. Nonetheless, failure to act involves criminal and immoral risk taking.

In deference to those learned skeptics who doubt that CO2 resulting from human activity is the cause of soaring temperatures, we are forced to concede that statistically, they have a 3 percent chance of being correct.  Yet it would seem morally reprehensible for us to act on the basis of such a flimsy margin given the potential for irreparable and irreversible harm to the earth’s ecosystem. If we choose to ignore the 97 percent scientific consensus and instead follow disdainfully the dissenting 3 percent, how will we be judged by future generations should the skeptics turn out to be wrong?

YAW/YAW