Natural variation and the greenhouse effect on air

The evidence clearly shows the global mean temperature at the Earth’s surface is hotter by 1.1 degrees Celsius (1.9 degrees Fahrenheit) than it was during the dawn of the Industrial Age in the mid-1700s. Remember: Mean means average and during that 270 or so-year span, there have been temperature variations (up and down). Overall, however, the global mean surface temperature or GMST has risen.

Trend-wise long-term, the Earth has experienced quite pronounced temperature swings – there have been periods of both warming and cooling. ”Interglacials” refer to times of warming, “glacials” being periods where cooling occurs, the back-and-forth switching between the two all part of a process called “natural variation,” from time to time such also referred to as “natural fluctuation” or “natural oscillation.” For the better part of the last 10,000 or so years, remarkably the Earth has been in a warming or interglacial phase, albeit somewhat different from those of times past. The most recent trend in warming has been truly unprecedented. That’s the difference.

Normally (a term used very loosely here) there is about a 10-degree-Celsius (C) shift, the change ranging from a low of -8 degrees Celsius to a high of +2 degrees C, the line of normalization being 0 degrees C. What’s extraordinary in the most recent case is the speed or time-frame of the latest almost 2-degree-C rise. It has occurred within just a couple of hundred years’ time, the greatest or sharpest or steepest increase taking place over the last half-century or so. Here again, it’s without precedent.

What people across the world have been seeing and/or feeling firsthand as of late are global warming’s effects. For more on this, see “Amplified by human impacts: Climate change.”

What is unknown or uncertain at this point is how long this current phase will last or just how hot the planet’s surface will get.

For some additional perspective, the previous record set for the most days in a year where daily high temperatures soared to 100 degrees Fahrenheit (F) or above in Fresno County (California) was in 1984 when there were 63. This year that record was broken, the new record being 68. That’s, in both cases, equivalent to more than 2 months’ worth. In fact, in 2021, the number of days when the temperature reached 100 degrees F or above would have been higher if not for smoke from area wildfires blanketing the county which helped on several days to keep temperatures below the century mark. What’s interesting is that in the winter before 1984’s so-called “hot-run,” 63-day record, California’s interior San Joaquin Valley received almost unheard of rainfall totals, 23 inches in Fresno County alone, well above from the normal or 11.5 inches annually!

The greenhouse effect – on air

The concept of the greenhouse effect – essentially heat being trapped in the air – is nothing new. According to Random House Webster’s College Dictionary, 1991 edition, Awareness of this phenomenon first came about in the years from 1935 to 1940.

If we assume – based on what is already known – that GMST will continue to rise and for some time to come, in what ways will this increase affect air pollution?

Considering what we already know about the impact of higher heat or temperature on weather, higher atmospheric heat results in increased evaporation rates from oceans and lakes, for example, which means higher precipitation levels if not more frequently occurring downpours of rain over land, and, if falling in the mountains at high enough elevations, snowstorms. As such, this could result in different areas across the globe being bereft of this type of weather, meaning for these places more drought and/or the extreme of desertification could be what’s in store. It could also lead to more incidences of blowing sand and dust. Blowing sand and dust being just one air-pollutant type.

Resulting also could be substantial loss in foliage and vegetation cover. As such, and when such die off, carbon is released into the atmosphere from that which has been stored in leaves, plants, trees, etc. – flora, in other words.

When we speak of Global Warming Potential (GWP) gases, when there is less flora, the carbon given up will need to seek alternative sinks such as in the air, in the seas and in land (soils). Some, invariably, involving human manipulation will be captured and injected deep in the ground, converted to other uses and interestingly if not ironically, captured and utilized to grow assorted crops and plants in what else?! Greenhouses.

Unlike some or even most kinds of pollutant emissions in our atmosphere which do not linger for appreciably long stretches of time, airborne carbon dioxide is different: It can stay aloft for decades. If, in fact, what is causing the Industrial Age’s GMST rise is the increase in carbon dioxide and other greenhouse-gas-emissions concentration in air and thus what’s fueling today’s climate anomaly which many experts believe to be the case, and, in turn, this creating a so-called “feedback loop”, one where each feeds the other, how we respond – or whether we respond at all – can have profound implications – good or bad – in terms of dealing with what is now being referred to by many as not only a climate crisis but an existential threat. Future life with a grossly altered climate could very well be what’s at stake.

That all said, at the same time, it bears repeating that roughly one-third of all carbon dioxide present in the atmosphere today can be attributed to human activity. The remaining two-thirds is naturally occurring.*

* Elizabeth Kolbert, “Under a White Sky: The Nature of the Future, 2021, pp. 147, 148

– Alan Kandel

All material copyright 2021.

The material in this press release comes from the originating research organization. Content may be edited for style and length. Want more? Sign up for our daily email.