Global Warming: The Scariest Warning Yet

 Much has been written about the hazards of continuing to burn fossil fuels and drive up the amount of carbon dioxide (CO2) in the atmosphere, but few have dared to identify the end game should humans continue on their merry way.  Ultimately, global warming will trigger processes that release huge amounts of CO2 and methane from natural sources that are potentially larger than human emissions and a point of no return is reached.  What would that mean for mankind? 

Mark Lynas dares venture into such end-of-times scenarios in his book Our Final Warning: Six Degrees of Climate Emergency.  Lynas is a British journalist and activist who in 2007 produced a volume titled “Six Degrees.”  The current book was motivated by the need to update future projections with the results of the research that has been provided in recent years.  The dire title was generated by the recognition that just about all projections in the past have been superseded by ones indicating more rapid effects of global warming.  To make that point, Lynas provides this possible timeline. 

“If we stay on the current business-as-usual trajectory, we could see two degrees as soon as the early 2030s, three degrees around mid-century, and four degrees by 2075 or so.  If we’re unlucky with positive feedbacks,,,from thawing permafrost in the artic or collapsing tropical rainforests, then we could be in for five or even six degrees by the century’s end.”

A change of 1.0 degrees C is equal to 1.8 degrees F.  A temperature increase of 6 degrees C is then 10.8 F.  It might seem that a few degrees change in average temperature is too small to produce the effects predicted, but it is the change in the extent of the temperature extremes that is critical.  We are already experiencing deadly heat waves producing many thousands of deaths.  Some areas of Earth experience temperature and humidity combinations that are near the point where the human body can no longer maintain itself at a viable temperature.  A few more degrees at the extremes could render habitation impossible without air conditioning for all.  Climate scientists insist that higher temperatures will lead to more intense weather effects: more severe floods in areas threatened by floods and more severe droughts where they are now threats.  We, at only a bit over one degree C in change, are beginning to suspect that climate change is already upon us.  Some of our most important food crops are already at risk during heat waves in our current environment.  Adding a few degrees to the temperature extremes will make crop failures much more likely.  Increasing temperatures will decrease crop yields at a time when the planet’s population is still growing—not a promising trend.

George Keeling is the scientist who began measuring the CO2 concentration and demonstrating its seemingly inexorable growth.  Its time-dependence is referred to as the Keeling Curve.  For Lynas this data proves the ineffectiveness of humanity’s paltry efforts and sets the stage for what is to come.

“…the rate of CO2 accumulation in the atmosphere is steadily increasing, from roughly 1 ppm [parts per million] in the early years to about 2 ppm annually today.  There is no visible slowdown, no sudden downwards blip, to mark the implementation of the Kyoto Protocol, still less 2009’s Copenhagen ‘two degrees’ commitment or the landmark Paris Agreement of 2015.  All those smiling heads of state shaking hands, the diplomats hugging on the podium after marathon sessions of all-night negotiating—none of that actually made any identifiable difference to the Keeling Curve, which is the only thing that actually matters to the planet’s temperature.  All our solar panels, wind turbines, electric cars, lithium-ion batteries, LED lightbulbs, nuclear plants, biogas digesters, press conferences, declarations, pieces of paper; all our shouting and arguing, weeping and marching, reporting and ignoring, decrying and denying; all our speeches, movies, websites, lectures and books; our announcements, carbon-neutral targets, moments of joy and despair; none of these to date have so much as made the slightest dent in the steepening upward slope of the Keeling Curve.”

Combining the results of recent observational data and improved modeling with the lack of any effective human response, Lynas has no choice but to expect an accelerated progression to ever higher temperatures—and the consequences thereof.

“When I started writing this book I thought that we could probably survive climate change.  Now I am not so sure…we are already living in a world one degree warmer than that inhabited by our parents and grandparents.  Two degrees Celsius, which will stress human societies and destroy many natural ecosystems such as rainforests and coral reefs, looms on the near horizon.  At three degrees I now believe that the stability of human civilization will be seriously imperiled, while at four degrees a full-scale global collapse of human societies is probable, accompanied by a mass extinction of the biosphere that will be the worst on Earth for tens or even hundreds of million years.  By five degrees we will see massive positive feedbacks coming into play, driving further warming and climate impacts so extreme that they will leave most of the globe biologically uninhabitable, with humans reduced to a precarious existence in small refuges.  At six degrees we risk triggering a runaway warming process that could render the biosphere completely extinct and for ever destroy the capacity of this planet to support life.” 

That may seem to some to be an outrageously over-the-top assessment.  However, we need to consider the fact that the planet, despite our recent stable century or two, has always been in an unstable equilibrium at best.  There have already been at least five occasions in the past when the planet got so far out of equilibrium that it caused mass extinctions.  In one instance about 90% of species disappeared.  These were accomplishments realized without our human assistance.  We should not doubt that we are capable of generating another mass extinction.  As best as scientists can tell, all these events were characterized by some combination of high temperature, high atmospheric concentrations of CO2, and oxygen-starved ocean surfaces—all of which we are putting in play.

Critical to the scenario Lynas has laid out are the feedback mechanisms that will inject additional CO2 into the atmosphere from natural sources.  A little survey of the planet’s carbon cycle is helpful in providing credibility.

The CO2 human activity contributes to the overall tally is dwarfed by larger natural sources and sinks.  The major sinks are absorption by the oceans and by terrestrial plants.  The major source comes from the decomposition of plant life.  Human activities, mainly burning fossil fuels, contribute a source of about 40 billion tons of CO2 annually, of which a little less than half remains in the atmosphere.  Decomposition of organic materials in the soil contributes about 100 billion tons annually that are almost balanced by the plant sink.  We contribute to the CO2 content of the atmosphere directly, but we can also contribute by altering the balance of the natural sources and sinks. 

About 50% of live plant mass ends up contributing to soil mass.  This soil mass increases over time.  Scientists believe there is nearly twice as much carbon stored in the dead biomass as in the living biomass.  Microbes break down the organic compounds in the soil and produce CO2 if oxygen is present and methane if oxygen is not.  The rate of decomposition will increase with rising temperatures.  Over geologic times this buildup can become quite large, and in some situations the organic materials are sheltered from decomposition.  This has occurred in the frozen permafrost regions in the northern hemisphere and in the bogs that form and grow in wetlands where plant growth far exceeds the rate of decomposition.  A warming climate will gradually melt the permafrost and provide a significant new source of greenhouse gases.  A similar process will occur with the bogs.  

Climate change can also alter the efficiency of the CO2 sinks.  Currently, scientific projections suggest that the Amazon rainforest, a major sink, could “collapse” under a drier climate as the temperature rises and become a significant source.  The wildfires that are spanning the globe are eliminating sinks and creating sources at the significant rate of about 7 billion tons of CO2 per year.  One can argue that this CO2 will be recaptured with plant regrowth, but there is evidence that the incidence of fires is growing as higher temperatures cause more rapid drying of vegetation, and the time lag associated with regrowth may be too large given the rate at which the climate is changing. 

Raising the temperature with our emissions will eventually throw the system out of balance and the sources could overwhelm the sinks leading to a runaway condition where our contributions are no longer needed.

No one can predict the exact temperature trajectory the planet will follow, and no one can predict the exact sequence of events that will ensue.  Nevertheless, we should keep in mind those five previous instances of mass extinction.  Messing with the climate is extremely dangerous.

You can learn a little about a lot of things or you can learn a lot about a very few things. Guess which is the most fun.