Too late to forestall the carbon dioxide Tipping Point, but what does it portend for global climate change?

Beginning in 1958 an American scientist known as Charles David Keeling devoted his life to meticulously and regularly track precise levels of carbon dioxide in the atmosphere until his death in 2005. He monitored carbon dioxide that is present in the atmosphere (atmospheric carbon dioxide) from a laboratory located on an isolated island volcanic mountain in Hawaii known as Mauna Loa. The exact place where Keeling undertook this work was the Mauna Loa Observatory set up by the U.S. Weather Bureau (now a part of the National Oceanic and Atmospheric Administration, NOAA). 

In the course of this period, the Mauna Loa Observatory has generated data that scientists have been using to draw firm conclusions to the effect that carbon dioxide emission levels over the last four decades have been increased by human activities generally and the burning of fossil fuels specifically. This accumulated carbon dioxide together with other greenhouse gases is responsible for global warming which has resulted in global climate change.

During the early phase of his work at the Observatory, Keeling discovered that the proportion of carbon dioxide in the atmosphere followed a similar pattern as the four seasons of the Northern Hemisphere namely: spring, summer, fall (autumn) and winter. During the spring and summer months, the demand for carbon dioxide by plants for photosynthesis raises dramatically as plants regenerate and grow. This means that the lowest levels of carbon dioxide in the atmosphere are recorded during that period. September, in particular, is the month when atmospheric carbon dioxide is at its lowest. The low point had never reached 400 parts per million (ppm) of dry air until 2016.

Conversely, during the fall months, decomposing organic matter (mainly leaves) emits an equal level of carbon dioxide back into the atmosphere, through respiration. For thousands of years, this two levels of atmospheric carbon dioxide remained relatively stable. 45 per cent of carbon dioxide released remains trapped in the soil, rocks and in the ocean while 55 per cent goes to the atmosphere.

Over time, Keeling’s data showed a dramatic pattern that had never been seen before. For each subsequent year from 1960, the level of carbon dioxide remaining in the atmosphere each year (the airborne fraction) was steadily increasing, resulting into what is now known as the “Keeling curve”. 

Keeling’s techniques for measuring carbon dioxide levels were so precise that scientist finally determined with sufficient accuracy that the additional carbon dioxide was the result of human activity and more specifically the burning of fossil fuels namely petroleum, coal and natural gas.

The steady increase in the level of atmospheric carbon dioxide over the four decades 1960 – 2000 led scientists to fear that levels of carbon dioxide would reach and exceed 400 ppm, a level that had never been reached for the previous 800,000 years. This level has come to be known as the carbon dioxide Tipping Point.

Exceeding the Tipping Point
As noted above, atmospheric carbon dioxide levels finally reached the Tipping Point in September 2016. From that date, the Earth’s climate reached a state it had never been in over the previous 800,000 years. The implication of this momentous event on the world’s climate is not yet very clear. Conventionally, climate scientists have relied on past events to model future climate scenarios. Since the Tipping Point was crossed, it means that scientists are looking at a completely new reality. What seems to be certain however is that extreme events such as floods, heatwaves and droughts that have already been observed in recent decades will most likely become worse if the assumption is that more greenhouse gases in the atmosphere means more global warming.

The most worrying adverse outcome of crossing the atmospheric carbon dioxide Tipping Point might be the fate of low lying small island states. Quite literary, some of them maybe doomed. Also likely will be increased coastal flooding and mixing of sea and fresh water along river deltas due to rising sea levels as well as increased acidification of sea water, which will alter the marine ecosystem in unprecedented ways.

In the absence of effective artificial methods to remove (sequester) more carbon dioxide from the atmosphere to keep minimum levels below 400 ppm, the world may not have seen the worst manifestation of the adverse effects of climate change. The present decade may prove to be the time when the world learns whether man has finally set himself on a path to self-destruction as a result of his disruption of the climate system.  It may well also be the time that new technologies for climate mitigation might prove to be the answer needed to forestall such a fate. The coming few years will certainly provide a clearer yet to be experienced glimpse of the consequences of crossing the Tipping Point.




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