Teaching Global Warming #1

I'm researching global climate change, ill-structured problem solving, and constructivist methodology for a paper/project. I know a decent amount about climate change, but expect I will learn a lot more over the course of the next few months. I think I will post a series of posts on what I find.

As of now I am kind of torn over this issue and how to teach it. It is one of my favorite parts of the year for several reasons: I find it fascinating, and most of my students find it interesting as well. The problem is that climate change has become a partisan issue. Democrats and liberals tend to believe every word Al Gore says about global warming, while conservatives dismiss it as junk science. As usual, neither are correct. My dilemma is how to teach a nuanced view of climate change to my 9th graders, or rather, to have them arrive at a nuanced view through critical thinking.

I usually start our time on climate change with a viewing of Al Gore's An Inconvenient Truth. The reason is that Mr. Gore actually does a pretty good job explaining much of the science of global warming and its potential effects on Earth. The collection of images and animations are top notch, and Al Gore seems to sincerely care about our planet. Most students are impressed and come away totally convinced that anthropogenic (human-caused) global warming is real and that we must act swiftly or else the world will end. This sort of thinking is encouraged by junk science movies like The Day After Tomorrow. Al Gore isn't quite that far down the alarmist spectrum, but he's pretty close.

After the video (my students take notes) we summarize as a class the various current and future effects global warming may have on the only habitable planet that we know of. These include glacial ice caps melting (which are an important source of fresh water), sea levels rising, a redistribution of precipitation patterns, ocean current changing, and many others. We discuss the basic science of the greenhouse effect (various gases, including CO2, absorb infrared light radiated from Earth and warm the atmosphere) and that humans contribute around 6 gigatons of CO2 to the atmosphere each year (for reference, around 3 million fully loaded 747's would equal 1 gigaton). Then I go on to point out some of Gore's mistakes and/or glossed over complexities.

For example, Gore's first illustration of massive glacial retreat is atop Mt. Kilimanjaro. Unfortunately, studies published by reputable scientists in peer-reviewed journals have shown conclusively that global warming is not the cause of the retreat. Rather, it is a pre-industrial revolution change in atmospheric moisture patterns that is responsible (also, the temperatures at that altitude never rise above freezing). This is not to say that other glaciers are not retreating due to warming temperatures, but Mt. Kilimanjaro was a poor choice by Mr. Gore, and in the interest of truth I feel compelled to point this out.

One example of uncertainty/complexity that Gore overlooks is the relationship between past CO2 levels and temperature. We are shown the data from ice cores from Antarctica that show the past several ice ages and the correlation between CO2 and temperature over the past 650,000 years. When CO2 levels are high, temps are high, and when CO2 levels are low, temps are low. You see, says Gore, CO2 levels control climate, and he goes on to show how our current CO2 levels are rapidly going off the chart in a vertical direction. The problem is that the published studies of these ice cores show that historically temperatures always rise first, followed around 800 years later by a rise in CO2 levels. Also, it is fairly well accepted that these climate changes, the change from ice age to interglacial period and back again, are ultimately caused by variations in the Earth's orbit, known as Milankovitch cycles (though various other factors also come into play). Gore's point though, or so it seems to me, is that in these ice cores we have clear evidence that CO2 has caused drastic climate change in the past and that we are about to experience apocalyptic levels of change due to anthropogenic CO2 emissions. This, to me, is a gross misuse of the ice cores to argue for a valid point: that rising CO2 levels likely will contribute to global warming. How do you explain this to freshmen in high school?

More coming soon.