Donald Trump has announced that the US will withdraw from the Paris Climate Agreement. The universal condemnation of this announcement has had the unintended consequence of bringing climate change to the top of America’s consciousness, which is a good thing, of course. Politicians from both parties have been critical of this decision, and the accelerating pace of reaction to this will certainly bring needed attention to the issue.
However, it’s important to recognize that anthropogenic climate change has been underway for more than one hundred years, primarily due to the burning of fossil fuels, but exacerbated by many other factors as well. We have been warned by experts for 50 years that if we didn’t address the causes, we would pass numerous tipping points, and there would be no second chances. For many reasons, it may be too late to do anything about climate change, other than prepare for a dystopian future.
Any engineer or mathematician can explain the concept of positive feedback. A system in equilibrium can be influenced toward a non-equilibrium state by external forces, and whether it returns to equilibrium depends on whether positive or negative feedback mechanisms are at work. Positive feedback tends to force the system further out of equilibrium, while negative feedback returns the system to equilibrium.
A pendulum at rest is a system in equilibrium. If it is pushed, gravity will cause the pendulum to return to its original position. Gravity is a negative feedback mechanism for this system. Friction will convert the energy from the initial push into heat, which causes the pendulum to come to rest, its equilibrium state.
A bowling ball on a table is a system in equilibrium. If it is pushed, gravity will accelerate the bowling ball toward the floor. Gravity is a positive feedback mechanism for this system. The ball will not return to its original equilibrium state, but will accelerate until the floor becomes its new equilibrium position.
The earth is a massive ecological system with many forces determining climate equilibrium, but unfortunately, anthropogenic global warming is an external force that has triggered numerous positive feedback mechanisms, and we have almost certainly passed the tipping points for many of them. Here are a few:
- Arctic ice: Once the earth starts to warm, arctic ice melts at an accelerated pace, which changes its albedo (ability to reflect light) from light to dark, thereby absorbing even more heat and accelerating the melting process until all the ice is gone. Without arctic ice, dark water will continue to absorb more heat, increasing ocean temperatures even more.
- Melting permafrost: Once the earth starts to warm, frozen permafrost regions in the northern hemisphere begin to melt, releasing trapped methane, resulting in more greenhouse gas in the atmosphere and further permafrost melting, accelerating the release of even more methane.
- Wetland peat: Once the earth starts to warm, wetlands dry out and peat fires become common, releasing CO2 into the atmosphere and accelerating global warming. Methane is also released from wetland peat bogs, resulting in more greenhouse gas in the atmosphere, accelerating the release of even more methane.
- Subsea floor: Once the oceans start to warm, sea floor methane hydrates begin to melt, releasing trapped methane, which vents to the surface, resulting in more greenhouse gas in the atmosphere, accelerating sea floor warming and the release of even more methane.
- Ocean sink: The oceans of the world can absorb large amounts of carbon dioxide, which makes them more acidic (ocean acidification is another severe climate issue, for another diary). However, as the ocean surface temperatures rise, CO2 solubility decreases, the transfer of CO2 from the atmosphere is inhibited, resulting in less absorption from the atmosphere, which accelerates the heating of the ocean surfaces even more.
- Rainforest die-off: The ability of the Amazon rainforests to absorb atmospheric CO2 may be decreasing. As the earth starts to warm, wildfires and drought increase in the rainforests, converting carbon stored in trees into CO2, which is released into the atmosphere, accelerating the heating of the earth even more. Fewer trees also mean less CO2 absorption, which removes one of the negative feedback mechanisms.
- Atmospheric CO2 levels: NASA scientist James Hansen has warned that atmospheric CO2 levels above 350 ppm, compared to pre-industrial levels around 280 ppm, would trigger melting of arctic sea ice and many of the other tipping points mentioned above. We passed 350 ppm in 1990, and we have continued to generate CO2 at an accelerating pace, resulting in continued increases in CO2 levels, assuring that the tipping points will not recover. In September 2016, we passed 400 ppm, permanently.
- IPCC climate scenarios: The only climate scenarios that the IPCC shows returning the planet to safe equilibrium levels involve removal of atmospheric CO2, not just reductions in CO2 production, i.e., negative emission technology. To date, no removal mechanisms are known to exist that can create the necessary CO2 removal rates.
Attention to anthropogenic global warming was an issue that needed to be addressed 50 years ago. It wasn’t. Now we all must prepare for the consequences, whatever those might be.
Do you agree or disagree? Take my poll.
Saturday, Jun 3, 2017 · 12:58:20 AM +00:00
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liberaldad2
I realize from some of the comments that I have caused a lot of consternation and despair out there. Although the story is depressing, many of us have come to live with this realization over several decades and have accepted its truth. The earth is headed for a new equilibrium. It will be different, but if it doesn’t kill us all, it may be an earth that we as a species can grow to love.
I owe all of you another diary to explain how one who understands and recognizes the consequences of human activity copes with day-to-day life. The quest for immortality is part of the human fiber. That will be a much harder diary to write, but I will try, because I think it’s important to keep this discussion hopeful. LA Times columnist Jack Smith famously said “The purpose of life is to keep on living and see what happens next.”