The Call, Column 60 – A Reminder

15 01 2017

(December 4, 2016)

The Urban Farmer

A Reminder

The Earth’s climate is changing, and human activity is the primary cause.          

            This statement is scientific fact, with no reasonable evidence against it. But it is also a call to action. And with each day that passes, as another 207 billion pounds of carbon dioxide are released into the atmosphere by human activity, it becomes a more dire warning.

Climate change is one of the simplest-to-understand atmospheric phenomena that exist. The Earth’s atmosphere undergoes what is known as The Greenhouse Effect. This is where certain “greenhouse gases”, which make up a small part of the atmosphere, trap the sun’s light as heat, preventing it from escaping back into space and warming the planet in the process. This is directly observable by the fact that you are not currently frozen solid. The Greenhouse Effect holds the temperature of the Earth’s atmosphere stable around 58°F, quite a bit warmer than the -400°F of the surrounding space. It also prevents the temperature from changing significantly (by 100s of degrees) between the day and the night, as it does on the surface of the moon and celestial bodies without Earth’s type of atmosphere.

Despite being present in low concentrations, carbon dioxide has one of the most potent greenhouse gases in the atmosphere. Geological records indicate that the Earth’s average atmospheric temperature has moved in lockstep with its carbon dioxide concentration. This is due to another straightforward chemical mechanism: the molecular structure of carbon dioxide makes it very effective at absorbing heat energy.

Prior to the growth of human industrial activity, the atmospheric concentration of carbon dioxide would change by very, very small amounts, or on a very large timescale, and within a limited range if at all, so that it was effectively constant on a short time-scale, and cyclic on longer ones. There are natural events which produce carbon dioxide – like animals exhaling, decomposition of organic matter, volcanic activity – and those which sequester carbon dioxide – plants inhaling, the formation of topsoil, deposition of fossil carbon within the crust of the earth. In a stable, cyclic system like our Earth’s carbon cycle, these effects naturally balance each other over reasonable periods of time.

This is called a “steady state”, and the same, in fact, is true of the Earth’s atmospheric temperature. While temperature isn’t the same one day (or season) to the next, it has always moved cyclically and predictably; so for example, the temperature in the week around the summer solstice of 1000 BC would be expected to be roughly the same as it had been in 1001 BC, 1025 BC, and 8000 BC. And the same variation in carbon dioxide concentration and temperature is expected – and observed – through every Ice Age Cycle (take a look at this graph: https://en.wikipedia.org/wiki/File:Carbon_Dioxide_400kyr.png). A similar carbon dioxide concentration and temperature occur at the peak of every Ice Age Cycle, and at every trough.

As expected, historically any event that shifted the concentration of carbon dioxide in the Earth’s atmosphere, over any timescale, was met with a similar change in the average global temperature and, as a result, changes in the Earth’s climate.

Burning fossil fuels has increased the concentration of carbon dioxide in the Earth’s atmosphere. This is simple chemistry. When you burn any hydrocarbon – the type of chemicals that make up fossil fuels – it releases carbon dioxide as a direct result of combustion. In the past 150 or so years, we have burned the better part of all the fossil fuel stored beneath the Earth’s crust. The carbon stored in those hydrocarbons was taken out of the atmosphere millions of years ago, when the concentration was higher, the atmosphere was warmer, and the planet had a lot less animals. The Earth has since created a new steady-state with a lower concentration of carbon dioxide. By burning that stored fossil carbon, we are increasing the concentration of carbon dioxide in the atmosphere.

This fact is also demonstrated by empirical observations. Carbon dioxide made up 280 ppm (parts per million) of the Earth’s atmosphere prior to the start of the industrial revolution, and has since increased by over 40%, to 400 ppm. This is likely the highest concentration in the last 20 million years, also shown in that graph I linked to above.

And that increased concentration of carbon dioxide over the past 150 years occurred simultaneously with an increase in average global temperature in the same timeframe.

Let’s review: The Earth’s atmospheric temperature is regulated by the Greenhouse Effect, which is driven by atmospheric greenhouse gases. Carbon dioxide is one of the most important greenhouse gases. Global temperature has historically moved in lockstep with carbon dioxide concentration, which itself has moved cyclically and predictably over large timescales. Burning fossil fuels releases enormous amounts of carbon dioxide, which was out of circulation for long enough that the atmosphere adjusted to its absence. Our use of fossil fuels over the past 150 years has been accompanied with a significant increase in carbon dioxide concentration – a 20-million-year maximum, well beyond natural geological cycles – and a similar increase in average global temperature.

Ipso facto…the Earth’s climate is changing, and human activity is the primary cause. This is the only logical conclusion to all of the evidence we have. And it is bar none the biggest problem we face as a species. The time to act is now.

My column appears every other Sunday in The Woonsocket Call (also in areas where The Pawtucket Times is available). The above article is the property of The Woonsocket Call and The Pawtucket Times, and is reprinted here with permission from these publications. These are excellent newspapers, covering important local news topics with voices out of our own communities, and skillfully addressing statewide and national news. Click these links to subscribe to The Woonsocket Call or to The Pawtucket Times. To subscribe to the online editions, click here for The Call and here for The Times. They can also be found on Twitter, @WoonsocketCall and @Pawtuckettimes.

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