In agreement with the study authors, Pounds and Puschendorf say taking immediate steps to reduce greenhouse gas emissions is imperative to constrain global warming to the minimum predicted levels and thus prevent many of the extinctions from occurring.
"The threat to life on Earth is not just a problem for the future. It is part of the here and now," they write.
The researchers based their study on minimum, mid-range, and maximum future climate scenarios based on information released by the United Nation's Intergovernmental Panel on Climate Change (IPCC) in 2001.
According to the IPCC, temperatures are expected to rise from somewhere between 1.5 and more than 4 degrees Fahrenheit (0.8 and more than 2 degrees Celsius) by the year 2050.
"Few climate scientists around the world think that 2050 temperatures will fall outside those bounds," said Thomas. "In some respects, we have been conservative because almost all future climate projections expect more warming and hence more extinction between 2050 and 2100."
In addition, the researchers accounted for the ability of species to disperse or successfully move to a new area, thus preventing climate change-induced extinction. They used two alternatives: one where species couldn't move at all, the other assuming unlimited abilities for movement.
"We are trying to bracket the truth," said Peterson. "If you bracket the truth and look at the two endpoints and they give the same general message, then you can start to believe it."
Outside of the small group of researchers working directly on the impacts of climate change to species diversity, "the numbers will come as a huge shock," said Thomas.
The researchers point out that there is a significant gap between the low and high ends of the species predicted to be on the road to extinction by 2050. Taking action to ensure the climate ends up on the low end of the range is vital to prevent catastrophic extinctions.
"We need to start thinking about the fullest of costs involved with our activities, the real costs of what we do in modern society," said Peterson.
Thomas said that since there may be a large time lag between the climate changing and the last individual of a doomed species dying off, rapid reductions of greenhouse gas emissions may allow some of these species to hang on.
"The only conservation action that really makes sense, at a global scale, is for the international community to minimize warming through reduced emissions and the potential establishment of carbon-sequestration programs," he said.
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