Global warming could mean more biodiversity on Earth, not less - just as long as we're prepared to wait several million years. In the short term, things don't look so good.
A study by British scientists of fossil and geological records for the last 540 million years suggests that biodiversity on Earth generally increases as the planet warms.
While warm periods have in the geological past brought more extinctions, they've also led to the rise of new species, increasing overall biodiversity.
Scientists had been surprised by the results of a previous study that analysed biodiversity over the same period, and concluded that a warming climate led to drops in overall diversity. But using an improved set of data, they found a slightly different picture.
The increase in biodiversity depends on the evolution of new species over millions of years, and is normally accompanied by extinctions of existing species.
Present trends of increasing temperature are unlikely to boost global biodiversity in the short term, therefore, because of the long timescales necessary for new forms to evolve.
"The improved data give us a more secure picture of the impact of warmer temperatures on marine biodiversity and they show that, as before, there is more extinction and origination in warm geological periods," says Dr Peter Mayhew of the Department of Biology at York.
"But, overall, warm climates seem to boost biodiversity in the very long run, rather than reducing it."
Ecological studies show that species richness consistently increases towards the equator, where it's warm, and the new findings fit with this pattern.
"Our results seem to show that temperature improves biodiversity through time as well as across space," says Professor Tim Benton of the University of Leeds.
"However, they do not suggest that current global warming is good for existing species. Increases in global diversity take millions of years, and in the meantime we expect extinctions to occur."
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