Basics of Climate Change

Over the next week or so I’ll be exploring some of the ideas and discussions generated from the UW Graduate Climate Conference.

Inevitably, whenever my field of study comes up in conversation I get the question, “So, is Global Warming real?”

It’s the kind of question that can’t really be explained in a two-minute party conversation. I usually try to emphasize the news media’s need to portray exactly two sides to every issue and the television ratings that are generated by a good controversy. I also point out that many of the issues debated in politics are different than the scientific discussion–there is some uncertainty as to the degree to which anthropogenic activity affects the climate, but the climate is certainly warming.

The climate system is immensely complex. The various biogeochemical cycles of the planet operate on timescales from days to millions of years; the earth’s climate has certainly had a rich and diverse climate history. Yet the basic mechanism of greenhouse warming is remarkably simple. Certain atmospheric gases–such as carbon dioxide, water vapor, and methane–are efficient absorbers and emitters of infrared radiation. If this effect were not in place (i.e., take all the water vapor, carbon dioxide, and methane out of the atmosphere) the temperature of the planet would plummet to -19 degrees Celsius (zero degrees Fahrenheit).

The atmosphere keeps the surface above freezing with this effect of absorbing radiation emitted by the surface and re-emitting it. With this same mechanism, if we increase the concentration of these greenhouse gases in the atmosphere, the temperature will increase–the math can be done at a high school level.

Since we know this fundamental relationship, we can then reason: if we emit carbon dioxide into the atmosphere, then it will have some effect on the surface temperature. The global carbon cycle is certainly robust, and we may very well not be able to account for all the sources and sinks of carbon, but emitting any amount of carbon dioxide will lead to some of it ending up in the atmosphere.

I’ve emphasized this point a bit because it is often confused or convoluted in the news media portrayal of the scientific discussion. There is certainly no question as to how human-induced activity could lead to warming surface temperatures. The uncertainties, rather, are 1) the magnitude of anthropogenic influence, and 2) the future projection of anthropogenic influence.

We can venture into these questions as well, though tentatively in some areas. We cannot claim to understand a system as complex as the climate, yet we also must face the things we can learn from it.