Critical Times

HUMAN-generated climate change is making flowers bloom sooner and autumn leaves fall later and is turning polar bears into cannibals and birds into early breeders, a global study has found.

Hundreds of previous studies had noted specific changes and most suggested a link to so-called anthropogenic (human-generated) global warming, but a new analysis published in the journal Nature correlated earlier studies with changes in temperature, the study’s lead author said.

The study found the early arrival of migratory birds in Australia, declining water levels in western Victoria and a 50 per cent decline in Antarctica’s Emperor Penguin population were linked to rising temperatures.

There was also a close relationship between temperature shifts between 1970 and 2004 and changes in plants, animals and the physical world, such as the retreat of glaciers and the water level in desert lakes.

“When you look at all of the glaciers and all of the snowpack and all of the birds laying eggs earlier and all of the plants having spring earlier across a continent, then we see we can detect anthropogenic signals,” said Cynthia Rosenzweig of NASA’s Goddard Institute for Space Studies.

Some of the observed changes in the natural world attributable to climate change were the early arrival of migratory birds to Australia and declining water levels in western Victoria; a 50 per cent decline in emperor penguins on the Antarctic Peninsula; cannibalism and decline in population of polar bears; glaciers melting in the European alps; and changes in 19 countries of leaf-unfolding and flowering of some plants; greater growth of Siberian pines in Mongolia; earlier break-up and thinning of river and lake ice there; changes in the freeze depth of permafrost in Russia; and melting Patagonian ice fields making sea levels rise.

The study’s authors ruled out observed changes that could have been caused by other factors besides anthropogenic climate change.

Ms Rosenzweig and her co-authors brought together nearly 30,000 sets of data about biological and physical changes around the world, then matched them with a detailed database of global temperature change.

The link between human-caused global warming – generated by industrial and vehicle emissions of carbon dioxide to produce a temperature-boosting greenhouse effect – and observed biological and physical changes was very strong, she said.

On a global scale, the correlation was more than 99 percent between the two factors; on a continental scale the correlation was between 90 and 99 percent.