Within a century, half of the world鈥檚 climates as we know them will have vanished forever as a direct result of global warming, taking thousands of species with them.
These are the gloomy projections of John Williams at the University of Wisconsin at Madison, US, and colleagues, who have carried out the first global assessment of how all of the Earth鈥檚 local climates will be affected as the world heats up.
New, previously unseen types of climate will also emerge, they say, with hotter temperatures and more rain.
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鈥淚t鈥檚 the coldest climates that would be replaced,鈥� Williams says. 鈥淭hey would be similar, in 100 years time, but several degrees warmer, so glaciers would retreat and ice would disappear from mountains such as Kilimanjaro in Tanzania.鈥�
Space invaders
New types of climate would emerge in more tropical regions, particularly the Amazon and Indonesian rainforests. 鈥淲hat we鈥檙e concerned about is what happens to the species in these regions,鈥� says Williams. The only options are migrating or adapting, but some will have nowhere to migrate to, or will be out-competed by invading species.
Williams鈥檚 team assessed the effects of warming on local and global climates using the latest projections developed by the Intergovernmental Panel on Climate Change for high and low emissions of carbon dioxide, the main greenhouse gas.
Comparing best and worst outcomes, the team estimates that 20% to 39% of the world鈥檚 land would develop completely novel climates, and existing climates would vanish in 20% to 48% of land area. 鈥淭here鈥檚 a big difference, so reductions in carbon dioxide do give cause for hope,鈥� says Williams.
Tropical mountains
A previous study, carried out in 2004, estimated that 15% to 37% of the world鈥檚 species would be committed to extinction by the year 2050 (see Global warming threatens millions of species).
鈥淭he new study extends that [2004] analysis and uses the latest climate change projections to highlight areas where current climates might disappear and novel climates may arise,鈥� says Andrew Watkinson, a climate researcher at the University of East Anglia in the UK, who was not involved in the research.
鈥淎s expected, disappearing climates are likely to be concentrated in tropical mountain regions and towards the poles, while novel climates will develop primarily in the tropics and sub-tropics.鈥�
Watkinson says that protecting biodiversity in the face of a changing climate is an enormous challenge, especially as climate change is not the only stressor. 鈥淢any of the areas highlighted in this paper are also subject to some of the greatest land use changes, especially in terms of deforestation.鈥�
Journal reference: Proceedings of the National Academy of Sciences (DOI: 10.1073/pnas.0606292104)
