The extinction risk of global warming is the risk species have of becoming extinct due to the effects of global warming. Many species are under threat, and when considered together this can be considered to be a potential mass extinction. Human extinction has also been predicted as an effect of global warming, although the adaptability of humans to widely varying climatic conditions reduces the risk of extinction compared to that of other species. James Lovelock has predicted only a 90% reduction in human populations due to global warming.
Climate change events in prehistoric times have been linked with mass extinctions. This may be directly due to the warming, as species become unable to adapt to new local climates and cannot move their ranges quickly enough (e.g. in the case of trees, which colonise new areas slowly) or at all (in the case of island-dwelling species). Extinctions may also due to the indirect effect of the warming on the chemical composition of the atmosphere or oceans. Such changes are a result of events caused by warming, such as an ocean anoxic event. An example of a mass extinction linked to climate change is the great dying.
The scientific consensus in the IPCC Fourth Assessment Report is that "Anthropogenic warming could lead to some impacts that are abrupt or irreversible, depending upon the rate and magnitude of the climate change." "There is medium confidence that approximately 20-30% of species assessed so far are likely to be at increased risk of extinction if increases in global average warming exceed 1.5-2.5°C (relative to 1980-1999). As global average temperature increase exceeds about 3.5°C, model projections suggest significant extinctions (40-70% of species assessed) around the globe."
In one study published in Nature in 2004, between 15 and 37% of known plant and animal species will be extinct or heading for eventual extinction by 2050. More properly, changes in habitat by 2050 will put them outside the survival range for the inhabitants, thus committing the species to extinction.
The abstract states:
Climate change over the past 30 years has produced numerous shifts in the distributions and abundances of species and has been implicated in one species-level extinction. Using projections of species' distributions for future climate scenarios, we assess extinction risks for sample regions that cover some 20% of the Earth's terrestrial surface. Exploring three approaches in which the estimated probability of extinction shows a power-law relationship with geographical range size, we predict, on the basis of mid-range climate-warming scenarios for 2050, that 15−37% of species in our sample of regions and taxa will be 'committed to extinction'. When the average of the three methods and two dispersal scenarios is taken, minimal climate-warming scenarios produce lower projections of species committed to extinction (18%) than mid-range (24%) and maximum-change (35%) scenarios. These estimates show the importance of rapid implementation of technologies to decrease greenhouse gas emissions and strategies for carbon sequestration.
Other researchers, such as Thuiller et al., Araújo et al. , Person et al., Buckley and Roughgarden, and Harte et al. have raised concern regarding uncertainty in Thomas et al.'s projections; some of these studies believe it is an overestimate, others believe the risk could be greater. Thomas et al. replied in Nature  addressing criticisms and concluding "Although further investigation is needed into each of these areas, it is unlikely to result in substantially reduced estimates of extinction. Anthropogenic climate change seems set to generate very large numbers of species-level extinctions." On the other hand, Daniel Botkin et al. state "... global estimates of extinctions due to climate change (Thomas et al. 2004) may have greatly overestimated the probability of extinction..."
Mechanistic studies are documenting extinctions due to recent climate change: McLaughlin et al. documented two populations of Bay checkerspot butterfly being threatened by precipitation change. Parmesan states, "Few studies have been conducted at a scale that encompasses an entire species" and McLaughlin et al. agreed "few mechanistic studies have linked extinctions to recent climate change."
The white lemuroid possum, only found in the mountain forests of northern Queensland, has been named as the first known mammal species to be driven extinct by man-made global warming. The White Possum has not been seen in over three years. These possums cannot survive extended temperatures over 30 °C, which occurred in 2005. A final expedition to uncover any surviving White Possums is scheduled for 2009.
- ↑ http://www.newscientist.com/article/mg20126921.500-one-last-chance-to-save-mankind.html?full=true
- ↑ Thomas, C.D.; Cameron, A.; Green, R.E.; Bakkenes, M.; Beaumont, L.J.; Collingham, Y.C.; Erasmus, B.F.N.; Siqueira, M.F.D.; Grainger, A.; Hannah, L. (2004). "Extinction risk from climate change" (PDF). Nature 427 (6970): 145–148. doi:10.1038/nature02121, http://www.mnp.nl/bibliotheek/digitaaldepot/20040108nature.pdf. Retrieved on 15 April 2008.
- ↑ Thuiller, W.; Araújo, M.B.; Pearson, R.G.; Whittaker, R.J.; Brotons, L.; Lavorel, S. (2004). "Biodiversity conservation: Uncertainty in predictions of extinction risk". Nature 430: 1. doi:10.1038/nature02716.
- ↑ Araújo, M.B.; Miguel B.; Whittaker, Robert J.; Ladle, Richard J.; Erhard, Markus (2005). "Reducing uncertainty in projections of extinction risk from climate change". Global Ecology & Biogeography, 14 (6): 529–538(10). doi:10.1111/j.1466-822X.2005.00182.x, http://www.ingentaconnect.com/content/bsc/geb/2005/00000014/00000006/art00004.
- ↑ Pearson, Richard G.; Richard G. Pearson, Wilfried Thuiller, Miguel B. Araujo, Enrique Martinez-Meyer, Lluıs Brotons, Colin McClean, Lera Miles, Pedro Segurado, Terence P. Dawson and David C. Lees (2006). "Model-based uncertainty in species range prediction" (PDF). Journal of Biogeography 33: 1704–1711. doi:10.1111/j.1365-2699.2006.01460.x, http://www.will.chez-alice.fr/pdf/PearsonJBI2006.pdf. Retrieved on 15 April 2008.
- ↑ Buckley, L. B; Roughgarden (2004). "Biodiversity conservation: Effects of changes in climate and land use". Nature 430. doi:10.1038/nature02717, http://www.nature.com/nature/journal/v430/n6995/abs/nature02717.html.
- ↑ John Harte; Annette Ostling, Jessica L. Green & Ann Kinzig (2004). "Biodiversity conservation: Climate change and extinction risk". Nature 430. doi:10.1038/nature02718, http://www.nature.com/nature/journal/v430/n6995/abs/nature02718.html.
- ↑ Thomas, C.D; Cameron, A.; Green, R.E.; Bakkenes, M.; Beaumont, L.J.; Collingham, Y.C.; Erasmus, B.F.N.; Siqueira, M.F.D.; Grainger, A.; Hannah, L. (2004). "Biodiversity conservation: Uncertainty in predictions of extinction risk/Effects of changes in climate and land use/Climate change and extinction risk (reply)". Nature 430, http://www.nature.com/nature/journal/v430/n6995/full/nature02719.html.
- ↑ Botkin, Daniel B.; et al. (March 2007). "Forecasting the Effects of Global Warming on Biodiversity". BioScience 57 (3): 227–236. doi:10.1641/B570306, http://www.imv.dk/Admin/Public/DWSDownload.aspx?File=%2FFiles%2FFiler%2FIMV%2FPublikationer%2FFagartikler%2F2007%2F050307_Botkin_et_al.pdf. Retrieved on 30 November 2007.
- ↑ 10.0 10.1 McLaughlin, John F.; et al. (2002-04-30). "Climate change hastens population extinctions" (PDF). PNAS 99 (9): 6070–6074. doi:10.1073/pnas.052131199, http://www.nd.edu/~hellmann/pnas.pdf. Retrieved on 29 March 2007.
- ↑ Permesan, Camille (2006-08-24). "Ecological and Evolutionary Responses to Recent Climate Change" (PDF). Annual Review of Ecology, Evolution, and Systematics 37: 637–669. doi:10.1146/annurev.ecolsys.37.091305.110100, http://cns.utexas.edu/communications/File/AnnRev_CCimpacts2006.pdf. Retrieved on 30 March 2007.
- ↑ http://web.archive.org/web/20081205100341/http://www.news.com.au/couriermail/story/0,23739,24742053-952,00.html White possum said to be first victim of global warming]