Yes, global warming could kill one-sixth of all species. It could also kill six-sixths of all species. There is nothing global warming cannot do. It might even cause an increase in speciation. Think of that! We’d have new kinds of animals we could serve up for dinner, all because of global warming.
Fig 2 from the Urban (2015) paper, demonstrating the end of the world.
Today’s headline was prompted by Mark Urban’s peer-reviewed paper in Science “Accelerating extinction risk from climate change“, which assures us that if we don’t “do something”, this is the end for a good chunk of life on earth.
Commenting on Urban’s work, the New York Times said “the real toll may turn out to be even worse.”
Yes, global warming could kill one-sixth of all species. It could also kill six-sixths of all species. There is nothing global warming cannot do. Why, it might even kill a negative one-sixth of all species—meaning it could cause an increase in speciation.
Think of that! We’d have new kinds of animals we could serve up for dinner, all because of global warming.
That global warming could kill or create species is a logical truth. It is also a logical truth that without human-caused global warming various species might die. What we’re interested in is the likelihood that one-sixth will die given everything we know about the planet and this solar system. Since all probability is conditional, we can make the prediction sound as dire or trivial as we like by being careful how we select our evidence. How careful is Urban?
He opens his paper by worrying about “the biological costs of failing to curb climate change”. A more scientifically ignorant thing to say is difficult to imagine (but give it time: people are always inventing ways of making mistakes). There is no way for human beings to stop climate change. None. Even if all mankind and all his artifacts were tomorrow to be projected into space, the climate on earth would continue to change. Even if mankind never existed, the climate would continue to change. We know these things with as much or more certainty than we know any other scientific fact. Stopping or preventing climate change is nevergoing to happen.
Here’s another indisputable scientific truth: short of a planetary ejection, there is no way to minimize man’s influence on the climate. The minimum would be no influence, and that is impossible so long as man exists. The best we can hope for is to ascertain what might happen given we were to do this or we were to do that.
Now what Urban did was a “meta-analysis”, which I often say is a statistical technique used to “prove” what individual studies couldn’t. The problem with all meta-analyses is that, since all probability is conditional, and all probability models are also, combining studies is often an exercise in slamming disparate evidence together with a 50 lb. mallet. Urban used a pneumatic hammer. Admittedly, he wasn’t working with prime material. The quality of the papers he examined was (statistically) poor.
Urban says the majority of studies he selected for his meta-analysis “estimated correlations between current distributions and climate so as to predict suitable habitat under future climates.” But others relied only on things like “expert opinion (4%).”
A correlation between the distribution of a species and the climate is not a certainty. Meaning that if the climate were to change, the distribution of a species might not decrease and that it might even increase.