What We Talk About When We Talk About Global Warming
by Gabriel Cross
The term “global warming” has fallen from favor amongst environmentalists, even as climate change deniers have picked it up as the perfect straw man. Not that anyone in the deniers camp was too keen on hearing the term last summer, when record temperatures were causing crop failures, but it was all we heard from them this past winter, when record snow fall put the east coast out of business for weeks at a time.
Because of this simple semantic trick, attacking global warming every time the thermometer is below average, for some time now the leaders of the green movement have been trying to replace the words “global warming” with “climate change.” This new term has its own flaws, as climates do naturally change over time, but somehow it seems unlikely that the term “accelerated anthropogenic climate change”(which is what we are really talking about) is going to catch on. Also, the term “climate change” does not capture a fact that “global warming” does, which is that globally and regionally average, mean, and median temperatures are likely to go up. The benefit of saying “climate change” instead of “global warming” is simply that proponents of the theory will not be aggressively attacked every time the temperature drops a little. Okay, they still will, but not with that particularly powerful straw man argument of “where’s your ‘global warming’ now?”
Ultimately, the debate about which term to use is a PR issue, and the attacks on the theory of global warming based on what the thermometer says right now are meaningless. Global warming isn’t about steady or dramatic increases in day-to-day temperature, it is about an increase in average temperature over the entire world over a long period of time, which might be expressed as record highs in the summer and record lows in other seasons, or dramatic warming around the equator and little change at the poles, for example, as long as it averages out to a net increase of 0.25`C over 25 years (which is the lowest projection for anticipated global warming over the next century).
Still, the term “global warming” is tainted, and the term “climate change” can seem a bit too vague or watered down. Both of these terms are merely words; they are ideas which have been used to describe a real-world physical phenomenon, and understanding that phenomenon is really the point of the debate in the first place. That phenomenon, expressed as simply as possible, is that there is more energy in the system. The troposphere, which is the lowest level of the atmosphere—the level where we live and where all of our weather systems occur—is holding onto slightly more energy than it used to, and that amount of energy is gradually increasing. This fact, that there is more energy in our atmosphere every year, is what is meant by the term “global warming.”
The sun adds energy to the earth every day and every day the earth loses some energy to outer space. This results in a net gain in energy all spring and summer, and a net loss in the fall and winter. Overall, there has been a pretty remarkable balance between energy lost and energy gained for millennia, with a few regular patterns of highs and lows along the way. However, for the past 200 years or so there has been an unusual increase in the rate of energy gained, or in other words a slight decrease in the loss-rate of energy. This extra energy can be expressed in many ways in the climate and the weather, the most obvious being increased temperature readings. However, another potential expression is increased moisture retention.
When water evaporates it absorbs energy from the air and lowers the temperature. The more energy there is in the system, the more water vapor the air can hold at the same temperature. The atmosphere changes its characteristics when there is more water vapor, and weather events can be more intense and/or more frequent. So global warming might not be expressed solely in the thermometer, but also in record storms, record or unprecedented weather events, and changing weather patterns.
Another possible expression of increased energy is increased wind and movement of air. Solar energy is one of only two things that get the air moving in the first place (the other is the apparent force of the earth spinning). Where the sun is particularly well absorbed (less vegetated areas, densely developed cities, large exposed rock formations, etc.) the air heats up faster and becomes more buoyant. The hot air rises, creating low pressure zones which cause surrounding air to rush in. The movement of the air is in effect extra kinetic energy held in the air that does not necessarily express itself as an increase in temperature.
These two facts—more moisture and higher winds—taken together in the right circumstances mean more tornadoes, hurricanes, tropical storms, and other weather events. In short, more energy in the system means more severe weather, and new types of weather events in different places.
The past couple of decades have given us new records, both highs and lows, and unprecedented storm events all over the world. Some areas are affected positively, and some very negatively. There are of course many statistical anomalies and counter intuitive results; the atmosphere is a very complex system. But, ultimately, recent weather and climate patterns hold together very well with the theory of what would happen if there were more energy in the system. Call it climate change if you like, or global warming if you are open to attack, but the reality is unchanged; the atmosphere is holding a little more energy every year. That increase means rapid, almost unprecedented change in climates and weather systems around the world in largely unpredictable patterns.
One cold day does not negate global warming any more than a record snow storm somehow negates the theory of climate change. Both can be unexpected but perfectly explicable results of more energy in the system overall, which is the physical phenomenon that was, for better or worse, initially dubbed “global warming” so many years ago. When you hear the words “global warming” or “climate change,” think “more energy in the system,” and suddenly record snow storms fit rather perfectly within the theory.