Why Is It Getting Warmer?

Before we begin, let’s clarify a couple of points. First, weather is day-to-day changes. Climate tracks those changes over very long periods of time. Second, global warming is the result of greenhouse gas emissions. Climate change is the result of global warming. The two are not the same.

Over the long run, changing climates can become either drier or wetter, colder or hotter depending on where you are. Day-today weather is subject to even more variables, so just because you have a cooler winter doesn’t mean a damn thing in terms of the validity of climate change.

There are four basic agents of change that contribute to climate changes that lead either to warming or cooling. Each impacts the other, so the long-term trend line may be clear even as the points on the line zig-zag back and forth.

Green House Gases (GHG): These are the leading sources of global warming. About half of GHG is CO2. Methane (the sleeping giant), freons and other assorted gases make up the rest. Two things to remember. Tiny amounts of CO2 and methane can absorb infrared light, preventing it from leaving the atmosphere. This IS the greenhouse effect. Second, they last a long time - thousands of years -- once they are in the atmosphere.

You will hear a lot of talk about water vapor, which is indeed the single largest source of the greenhouse effect. In fact, we wouldn't be here if water vapor had not warmed the earth to a temperature favorable to life.

Here's the thing. There is a humongous amount of water vapor present in the atmosphere, so human activity in and of itself has little direct effect on the amount of water vapor. On the other hand, there are only very small amounts of carbon dioxide and methane in the atmosphere, so the little bit added by human activity has a disproportionate effect.

On top of that the GHG act as a multiplier by increasing the amount of water vapor in the air which makes the earth even warmer and also has effects on rainfall, making drier areas drier, wetter areas wetter and both more susceptible to heavier damaging rainfall events.

Sulfur Emissions From Burning Coal: The good news is that this can and does offset the warming affect of GHG. The bad news is that sulfurs are relatively short-lived, maybe a few years at best. The irony is that countries are working hard to reduce sulfur emissions, which is good for reducing acid rain but which could end up accelerating the pace of global warming (assuming that it is real, of course).

Volcanoes: In a way, this is just more of the same, in this case sulfur, which is injected into the atmosphere during an eruption. The cooling effect can be quite massive, but as has already been noted, relatively short-lived. And of course there is the fact that there is no way to know when a volcano will erupt.

Variations in the Intensity of the Sun: Despite all the recent talk, this has the least impact on climate change as compared to the other three. When sun spots are plentiful, the sun puts out more heat which amps up the ultraviolet rays which in turn amps up the ozone layer. When sun spots diminish, as is the case right now, the net effect is a cooling of the atmosphere, which offsets other warming factors.

My feeling is that it doesn't matter why the earth is getting warmer. And it is no help to say that this has happened many times in the planet's history. All of that is true. The difference maker is us, all 6.7 billion of us, nearly 1 in 10 of whom live in low-lying areas of the planet directly threatened by rising sea levels and extreme weather.

Never before has the planet been so crowded with people. Never before have we as a race faced so potentially grave and universal a crisis where so many of us will be competing for resources and a safe haven. That is why it matters.