Throught the last couple of decades there have been an enormous number of statements about how anthropogenic global warming (AGW) will bring about the “end of the world”, or the end of most life on earth, or at the least environmental Armageddon. I used to follow all of the “bad things” that were going to happen because of AGW, but it became to unwieldly and difficult to keep track of it all and once climate prognosticators started predicting the loss of nearly all life on earth – what would be the point of continuing the list? Besides, there seems to be a more comprehensive list here.
One of the more extreme predictions is that we will suffer a “run-away greenhouse effect” and end up like Venus, a toxic furnance of a planet.
This topic came up again in TechnologyReview, where James Hansen claims a runaway greenhouse effect is certain if we burn up all the fossil fuel on earth. Other physicists are not so certain, but leave the door open. Not me. I usually couch my predictions in the terms of likely or unlikley, very little chance or extremely probable. I hardly ever speak with 100% or 0% certainty on anything. With the “run-away greenhouse effect” I am very close to 100% certain it will not happen. 99.99% would probably capture the certitude.
There are many reasons why a run-away greenhouse effect is very unlikely. First of all, the use of fossil fuels is dynamic and self-limiting. There is less cheap fossil fuel available today and the price has gone up. The price will continue to rise in coming years. It is not getting any easier or cheaper to retrieve fossil fuels. We won’t end up burning all the oil in the world if the price rises to $200, $300, or $500 dollars a barrell. Economies will crash. Fossil fuel usage will decline in kind.
Secondly, the negative effects of AGW (if they happen) is self-limiting on the usage of fossil fuels. If food webs collapse and billions of people die before 2100 (which has been predicted), then how likely is it that human society will continue using and buring fossil fuels at an increasing rate? Near zero chance, wouldn’t you say. If some of the predicted effects of AGW would start to appear and more people begin to suffer then society as a whole would take more agressive measures to counteract AGW. I am not only talking about reducing fossil fuel usage, but actually taking carbon dioxide and other “greenhouse gasses” out of the air. It is possible with today’s technology (check the end of this blog entry) and it will become more practical in the future – if this mitigation effort is needed. Economically, socially, and technologically speaking, a runaway greenhouse effect would have to begin TODAY and wreak its devastation within years, not decades, in order for it to be plausible. Self-limiting factors would otherwise come into play on longer time scales.
On a more fundamental note, no one is for sure how Venus ended up the way it did. There is not enough information ab0ut the planet to know whether it was once “cool” like the earth, or if it suffered a runaway greenhouse effect. It is pure theory and speculation. Comparisons of Earth and Venus are rather tenuous.
In the TechnologyReview article linked above, it is stated that we cannot be too sure about a runaway greenhouse effect because “atmospheric physics is so complex that climate scientists only have a rudimentary understanding of how it works.” It kind-of makes one wonder how the “science is settled” in AGW predictions and why the “debate is over”.
In the end, the runaway greenhouse effect is an interesting mental excercise for theoretical physicists and climate scientists and we can probably gain some insight by thinking about it a little, but the odds of it happening are so low that we should be focusing a lot more brainpower on inventing a cleaner future.
Have a nice Friday! Meteorologist Justin Loew.
This post was written by jloew on January 13, 2012