“The Earth is warming,” a self-professed skeptic said last night when nine of us met to discuss the Gore movie, “but how do we know it is not from natural causes?” I’ve rephrased what he said as a question, but he didn’t actually have any questions, which may make him less a skeptic and more a denier.
So is there a way to differentiate, do the different causes of climate change have different fingerprints which can help us distinguish among them? Yes
For example, if increased solar activity had heated the Earth almost 1.5 F from 1900, which would be warming faster, day or night? winter or summer? Would the stratosphere be warming along with the troposphere (lower atmosphere)?
The results are different from what increased solar activity would produce: nights and winters are warming much faster. The stratosphere is cooling because the increase radiation from the sun is relatively small compared to the increase in the amount of heat that the Earth is holding onto.
Additionally the tropopause is rising. The tropopause is the boundary between the troposphere, where temperature goes down with altitude, and the stratosphere, where temperature goes up with altitude. The mixed in GHG have spread to the top of the troposphere and a little beyond, and now it’s larger, 200 meters higher than in 1979.
A lot of it is the decrease in atmospheric ozone — but look at the graphs a little over midway down to see the enormous effects of pollution (sulfate aerosols) on cooling the Earth — this is only temporary, if we stopped using coal today the pollution would go way down and the GHG would stay for much longer. Also coal power kills tens of thousands of Americans each year, and many many many more each year in China, and continuing to kill these people so we can continue to mask the effects of rising GHG doesn’t seem like such a wonderful solution.
The tropopause information is very detailed. The ozone depletion contribution is stronger in the southern hemisphere. The effect of sulfate aerosols is stronger where most people live, in the northern hemisphere. Because the data that allowed the tropopause conclusion is so detailed, it allowed scientists to identify another fingerprint of global warming caused by GHG.
The denier excepted, I was heartened so many came together with a desire to “do something”. An easy something to start with is to begin the conversation with people you know. I heard once, and it may even be true, that when 20% of a group changes its mind, the group begins to respond.
The argument here is very convincing, but there will still be some people who won’t accept it. Even if the denier is right, however, it doesn’t follow that we can continue burning fossil fuels at the rate we are burning them. Our overuse of fossil fuels has bad effects in addition to climate change, among them polluted air and water, destruction of water runoff by paving for automobiles, a man-made environment that is increasingly disheartening and ugly, and a great deal more. The remedy for these troubles is the same as the remedy for climate change: end or sharply reduce our dependence on fossil fuels.
That’s not to suggest that the denier is right, only that his implied conclusion is a non-sequitur. Whether one is concerned about pollution or about climate change, the end result is the same: we’ve got to stop burning fossil fuels.