Why 2 degrees is the number in the climate-change crisis
- Randi Pokladnik
- April 5, 2019
- 2134
Scientific consensus states we must maintain the earth’s global average temperature to just 2 degrees Celsius above what it was during the pre-industrial revolution era. In order to do this, Yale economist William Nordhaus said in 1975 we must keep our greenhouse gas emissions at an amount that is double what they were pre-industrial revolution.
The average global temperature on Earth has increased by about 0.8 C (1.4 F) since 1880, but places in the Arctic are 25 F higher today.
A 1990 report by the Stockholm Environmental Institute initially recommended only a 1-degree increase in the global average, but this was deemed unachievable, so 2 degrees became the new target.
Throughout the past 30 years, scientists have maintained this is the goal we need to achieve. They realized increases in temperature could rise exponentially not linearly and we may experience unprecedented high temperatures.
Many scientists feel we are reaching a tipping point when it comes to climate change. A tipping point happens when a small change can trigger a major change.
Think of it this way: Our blood pH is slightly alkaline at 7.35 -7.45. When it drifts just slightly in either direction from this range, major life-threatening health issues can occur. The website, CarbonBrief.org, has excellent graphs to show how a small 0.5-degree temperature increase can affect outcomes of climate change.
Earth’s climate is now dealing with positive feedback loops, where one variable will increase an affect, which in turn increases the affect of the first variable. Positive feedback loops in our climate include things like albedo effect, melting arctic methane hydrates, soil carbon and forest fires. These can push the planet toward the tipping point by accelerating the warming of our planet.
Albedo effect refers to the Earth’s reflection of sunlight. Similar to wearing white clothes in summer, the Earth’s Polar Regions act to reflect sunlight or solar radiation. Snow and ice reflect radiation while ocean water and soils absorb radiation.
Once the polar ice is melted by rising temperatures, land and oceans will absorb solar radiation rather than reflecting it. A positive feedback loop has begun; higher temperatures melt more ice, water and exposed land absorbs more heat, the atmosphere warms more, and then more ice melts.
Melting arctic methane hydrates are another positive feedback loop. The first time I heard the term “methane hydrates” it was in a story about ice catching fire. In actuality ice cannot catch fire; however, when methane hydrate is melted, it will release flammable methane gas. These substances are common in arctic ice, permafrost and the continental shelf around the world.
Methane hydrate is formed when organisms break down organic matter and the resulting methane molecule becomes encapsulated between frozen interlocking water molecules. It is like a methane cage of sorts.
As Earth’s temperature rises, more and more of our arctic ice and permafrost melts and releases yet more climate-changing methane gas. The thawing of permafrost is so bad that in some places trees no longer held by frozen soil are tilting like they are drunk.
Recently it was reported the Svalbard Norwegian Seed Vault 1,300 kilometers from the North Pole is being affected by melting permafrost.
Methane gas is an especially dangerous contributor to climate change. It is 86 times as potent as carbon dioxide when it comes to its heat-trapping ability, according to the Intergovernmental Panel on Climate Change.
NASA has reported man-made emissions of methane have increased significantly, and much of the increase is due to fugitive emissions (leaks) from the process of fracking.
Another positive feedback loop in our ecosystems is the terrestrial carbon cycle. This is the cycle of carbon as it passes from air as carbon dioxide to vegetation as a carbohydrate to soil as organic carbon and then back into the atmosphere as carbon dioxide via decay and respiration. The journal, Science, recently reported some alarming results from a 26-year study of carbon-soil cycling.
The experiment took place at the Harvard Forest located in Petersham, Massachusetts. For the carbon-soil cycling study, plots of soils were artificially heated to about 5 degrees warmer than surrounding soil. This was done with buried electric cables similar to the heat tape placed on pipes in the winter.
They found less carbon dioxide was absorbed by warmer soil plots. In a nutshell warmer soils hastened decay, leading to more carbon dioxide releases. The heat also affected the ability of microbial ecosystems in the soil to use carbon and keep it out of the atmosphere.
Another study just published in Nature magazine this year spoke about the effect of soil moisture on the ability of land masses to absorb man-made carbon dioxide emissions.
Currently 25 percent of our carbon dioxide emissions are absorbed by the terrestrial ecosystems. Increasing droughts and loss of vegetation could lower this number significantly.
The final positive feedback loop is the contribution of particulate matter and carbon from forest fires to the absorption of solar radiation. In the past 20 years forest fires in the Western U.S., Central Canada and parts of the Mediterranean have become much more frequent and more devastating.
The warming of the atmosphere is causing more fires, and coupled with the lack of snow melt in some regions, these fires have blackened millions of acres. The blackening of the once green land area is causing more solar radiation to be absorbed and less carbon dioxide to be sequestered.
Additionally particulate matter from fires can be found as far away as the Arctic or Greenland, where the soot in the form of extremely small (less than 2.5 microns) carbon particles also adds to heat absorption.
There are many other events occurring across the globe that also may play into the possibility of runaway, rapid climate change. Scientists can only use models to try and predict climate; there are no guarantees.
When it comes to the catastrophic weather events currently happening, like the flooding in Nebraska or Cyclone Idai in Mozambique, it is better to err on the side of releasing less carbon dioxide and methane.
We have the data, knowledge, technology and skills to turn climate change around before the 12-year deadline when we will see wide-ranging damage. But as long as we lack the political will and the ability to stop the continued expansion of fossil fuels, we will be playing Russian roulette with the tipping point.