At the Cliff of Climate Catastrophe
With the release of a new report on climate change, Earth may be at a tipping point
On August 6, 2021 the Intergovernmental Panel on Climate Change (IPCC) published the first section of its sixth assessment report. Their findings were stark. 1.5 degrees Celsius of warming was envisioned as a red line of sorts, not to be crossed or the worst effects of warming would be felt, with the Earth permanently altered:
“Many changes due to past and future greenhouse gas emissions are irreversible for centuries to millennia, especially changes in the ocean, ice sheets and global sea level.” -Climate Change 2021: The Physical Science Basis (AR6)
However, we are currently on track to meet and exceed this upper limit:
“[The report] finds that averaged over the next 20 years, global temperature is expected to reach or exceed 1.5°C of warming.” -
In biology, the term ecological threshold is used to describe when an event can trigger drastic changes in an environment. Picture an ice cube sitting on a table. If the outside temperature rests at at below 0 degrees C, the ice cube remains a solid, frozen, orderly mass. Increasing the temperature past the freezing point shifts this ice cube into a new, liquid state. The liquid may be cooled down to freezing again, but unless it is placed in a cube-shaped container its shape will be permanently altered- it is no longer a cube as it once was.
Let’s extend this analogy to an complex environmental system, say a forest. Most ecosystems have resilience, an ability to maintain or recover its function after some disturbance. A natural wildfire may seem to be catastrophic to the casual observer. Tall trees are scorched and killed, untold thousands of animals and plants are consumed by the blaze. However, natural fires play a crucial role in recycling nutrients back into the soil, and can even serve as a mechanism for new growth. The steady state of a functioning forest is temporarily altered, and then over several years and decades, returned to and renewed.
Humans are notoriously good at creating conditions for crossing ecological thresholds. Say the same forest was cleared for agricultural land. Now, not only is the canopy gone, but so are dead trees and debris, vital for animal habitats. Introduced livestock strip the ground of small vegetation, and radically alter nutrient cycling from their manure. Native wildlife find themselves homeless or out-competed, and begin to move or die off, as food webs morph and degrade. Even with the humans gone, the landscape and community is changed forever. Even if we were to plant new trees, replace the soil, and reintroduce native species we could only attempt to approximate past conditions, never quite reaching them.
One such threshold with regards to climate is the melting of the Arctic permafrost. For tens of thousands of years, methane and carbon dioxide have been trapped under the ice and within the soil. It has acted as a carbon sink, absorbing and safely storing these greenhouse gases. But as the arctic thaws, these gases release, causing more warming and thawing. This could lead to a positive feedback loop- a runaway warming cataclysm. Even if we were to cut our emissions to zero, this effect may still be underway and unstoppable.
A similar process occurs the melting of snow and ice cover. Ice has a high albedo, or reflectivity. Sunlight hitting ice will have most of its energy reflected, and not absorbed. As more bare land or water is exposed, the albedo is decreased and more thermal energy is absorbed, causing more melting. From a combination of these feedback loops among other influences, global warming has a disproportionate impact on the arctic and Earth’s coldest regions.
Climate is confusing, abstract, and most in the news media lack formal scientific education. The result is a blip in the headlines for a few days. Natural disasters (such as the wildfires in California or flooding in China) receive some attention, and lip-service is given to climate change during its coverage, but this pales in comparison to political news, manufactured outrage and celebrity gossip. The latest environmental disaster becomes a conversation piece at the dinner table, and is quickly forgotten about. Because climate change effects the whole planet in often subtle ways, it can make for a poor story to drive ratings. Our leaders pass tepid laws and decades-long “solutions” when the problem requires urgent and concerted action.
Looking back at earth’s natural history reveals a startling fact: the concentration of carbon dioxide in the atmosphere not only corresponds to Earth’s average temperature, but climactic shifts shifts are a main cause of great extinction events. For instance, the Permian mass extinction, which may have wiped out as much as 90 percent of life, coincided with a seawater increase in temperature of as much as 6 degrees C.
Earth is now at its warmest in roughly three million years. When natural fluctuations in Earth’s temperature take place over thousands and millions of years, and human-induced climate change has occurred in several hundred, this is an unprecedented event in Earth’s history, and a major stress test for the flora and fauna that live here. Indeed, it is clear to many in the scientific community that we are living in the sixth mass extinction event, one that is caused not by some geological or astronomical phenomena, but by us, with climate change a main contributor. We are already peering down the edge of the climate cliff. What happens when we fall?
