1/5/17

Climate Change #3 – Carbon, Temperature & Geologic History

Over my last two blogs, we discussed climate variation driven by natural phenomena such as the physics of the earth and sun, as well as greenhouse gases (GHGs). While both play key roles in climate change, it has hopefully become clear that on the time scale of present day climate change, it's GHGs and not natural phenomena that are steering the ship. This is the science. Not the politics.

In this blog, let’s look at the relationship of temperature and GHGs from past to present. First, let me remind you that GHGs aren’t new to the air. It’s in fact the presence of GHGs that have enabled a habitable temperature on earth by trapping solar energy. But don’t let this throw you off. It doesn’t take much GHG to have a warming effect. Throughout human history, GHGs have in fact made up only about a meager 0.03% of the atmosphere. Compared to the 21% oxygen we breathe, that’s basically a drop in the bucket! So what we’re talking about with present day climate change is a change in this very modest 0.03%. Over the last 200 years, the burning of fossil fuels have added enough GHG into the atmosphere to increase this to 0.04%. Yes, we’ve always been talking about small fractions. But the percent change from the old small fraction to the new small fraction is enormous—an increase of 33%! Actually, I’ve been rounding numbers; the true increase is over 40%.

If you added 40% more salt to your dinner, ate 40% more calories, or exercised 40% more often, there’s little doubt the change would be noticed. Change of course wouldn’t be instantaneous, but rather over the coming weeks or months. With earth, a 40% increase in GHGs is similarly a tremendous shift from the norm—a shift that will also bring no subtle change. Except, rather than noticing change over weeks or months, we’re talking years to decades. And as the years pass, we’re indeed observing this change. How much change will occur still depends on how quickly we adopt more modern energy technologies are reduce GHG emissions. But the sky is the limit (no pun intended!). Remember, an atmosphere with 0% compared to 0.03% GHGs has been the difference between a frozen earth and the comfortable earth on which our ancestors roamed. Moving then from 0.03% to 0.04%, as we’ve done over the past couple hundred years …well you can only imagine the possibilities! And 0.04% isn’t where it stops. Given the current rate of carbon emissions, this percentage will only continue to grow.

So you know that GHGs trap sunlight and thus warm the planet, and you know GHGs have been skyrocketing since the industrial revolution. But sometimes a picture (or graph) is worth a thousand words!



In the above graph, notice two key things. First, temperature and carbon dioxide (the major GHG) are indeed highly correlated through geological history. This isn’t a shocker given what we know about the warming effects of GHGs, but it’s nonetheless powerful to see the data. Second, modern day carbon dioxide is literally off the charts (top right of graph). If we extend the graph further to the left, as shown below, you’ll notice carbon dioxide concentrations are actually higher now than at any point in the last 800,000 years.



In short, we’re in completely uncharted territory in terms of climate—a planetary experiment if you will. Both graphs are worth a moment of pause and thought. The million dollar question being, how will the red line in the first graph ultimately respond to the blue line? There are many scientists whose careers are dedicated to answering this question. But I’ll save discussion of long term implications and temperature projections for a later post.

If you’ve taken the time to read this, congratulations! You now understand the climate change issue better than most. Now it's your turn to educate others. Please share!   

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Shahir Masri
Doctor of Science
Environmental Health Science


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