Sustainability 101: Climate Change (Part 2, Climate Chemistry)

In my last article I reviewed one of the tools that climate scientists use to understand what the Earth was like long before we were here. It's said that "history repeats itself," and we have a 100,000 year repeating cycle to prove it. If the planet maintains this heartbeat of warming to a final crash into an ice age, we have been on the precipice of a frozen world for quite a while. This is not normal.

Chemistry of Climate

So what happened? Through quite a bit of investigation and experimentation, scientists determined that carbon dioxide (CO2) is one of the main culprits. CO2 occurs naturally as a result of biological processes and is taken in by plants when they photosynthesize. It’s also released in large amounts through industrial processes like burning fossil fuels or agriculture.

There are other greenhouse gasses, but for this explanation I will focus on the most widespread – CO2.

Why CO2?

CO2 is somewhat unique when it comes to the behavior of natural atmospheric gasses. Unlike oxygen or nitrogen, which make up most of our atmosphere, CO2 can interact with infrared (IR) radiation – heat energy. The simplest analogy I can present is that a CO2 molecule exists like a miniature trampoline (simple animation here). Heat energy strikes the molecule, CO2 holds that energy for a brief second, then the energy bounces back away from it. We know CO2 behaves this way because it’s a measurable quality, observed through direct laboratory measurements.

CO2 reflects IR radiation in a very important band of energy, the peak of IR that is emitted from the Earth. Plus, it is environmentally stable, staying in the atmosphere unless there is a drawdown – like plant life – that removes it from the air.

What this all means is that a range of energy comes to our planet from the sun - UV radiation, light, some IR. At the surface of Earth this turns into IR energy. You experience this yourself when you're outside in the sun, feeling warmer in sunlight than in the shade, even though the air temperature is the same in both places. This is because you're feeling heat energy when light energy turns to IR (heat) energy. IR energy then bounces back, moving up through the atmosphere. Some of it naturally gets trapped, which is normal. However, if we have more and more of those tiny IR-reactive CO2 trampolines in the air we'll be trapping a lot more heat than what is normal.

OK so CO2 interacts with IR in the lab – but in the wild?

Scientists have made good use of the satellites that we have orbiting the planet. We can measure the energy spectrum coming from the sun, and the spectrum that hits the ground. The difference between the two is what the atmosphere filters out.

Likewise we can observe the energy leaving the Earth, and using satellites measure what of that energy is trapped by the atmosphere on its way out. Below is an annotated comparison of the blackbody radiation of the Earth (maximum amount of energy that would be emitted if nothing were blocking its escape), and the observed amount of energy reaching satellites. You can see that the greatest source of IR blocking at the peak is CO2. This energy is trapped within our atmosphere.

How Much CO2 Is there Today?

In the 1950s, an observatory on Mauna Loa in Hawaii began a consistent monitoring project of the Earth’s atmosphere. It’s the world’s oldest continual monitoring station for atmospheric CO2 levels. It is a great location to do this, as it’s on a mountain high above ground-level interference, and far from any continent where land-based influences are minimal.

If you have seen “An Inconvenient Truth”, or the many parodies or references out there of it (The Simpsons did it, of course), you know where I’m going with this. The Mauna Loa measurements of our background CO2 levels are way above the amounts you see in the ice cores. Note that below is a January 2017 graph from NASA. We’re now at 410 ppm CO2.

We’re in uncharted territory here, requiring reliance on climate models that take into account those longer-scale Milankovitch impacts, calculations of IR energy entrapment (heat energy stuck in the atmosphere) with increasing CO2 levels, and other weather impacts of increased temperature (humidity, energy available for storms, etc).

That being said, how bad can it get, really...?

To be Continued...

Thank you for joining me for this Sustainability 101 explanation. There is a lot of ground to cover in this series, so please join me for upcoming articles on subjects like climate change and science-based targets, the UN’s Sustainable Development Goals, and solutions like RECs, carbon offsets, and carbon taxes.