A new study reveals that shrinking glaciers, plants blooming earlier across Europe and lakes declining in productivity in Africa can all be linked to human-caused climate change since 1970.

These findings were published in the journal Nature on 15 May 2008.

The IPCC Working Group II had previously found that anthropogenic warming (warming caused by human activities) is likely to have had an influence on many physical and biological systems.

This study goes further to link specific observed changes in nature, even on particular continents, to increased greenhouse gas concentrations over the last 50 years.

“We are seeing the impacts of human-caused climate change in many natural systems much earlier than previous studies had projected. Without urgent action to slow global warming, much larger changes will occur” said Professor David Karoly from the Department of Earth Sciences at the University of Melbourne.

Researchers from NASA, the University of Melbourne and several other international institutions built a database of over 29,000 observed changes (from over 80 research papers) in the natural world including physical features like melting permafrost and biological responses like bird migration.

A unique feature of the study is that it combined observed impacts in physical systems, such as shrinking glaciers, melting permafrost, earlier spring peak discharge, and warming lakes and rivers, and biological responses such as leaves unfolding and flowers blooming earlier in the spring, migrating birds arriving earlier, and ranges of plant and animal species moving towards the poles and higher up mountains finding that in oceans, lakes, and rivers, plankton and fish are shifting from cold-adapted to warm-adapted communities.

They analyzed the data to see whether the changes were attributable to climate change or could have been due to factors such as land-use change from forests to agriculture or from agriculture to urban areas.

Using a process called ‘joint attribution’ they showed, at the global scale, that observed changes in diverse physical and biological systems are consistent with warming, that the global agreement between the spatial patterns of observed impacts and of temperature trends is beyond the range of natural variability, and that the observed global-scale warming is very likely due to human causes.

The authors further demonstrated that the influence of anthropogenic climate change on physical and biological systems can be seen at continent scales.

The continents that show agreement between the spatial patterns of observed warming and impacts are Asia, North America, and Europe.

In the other continents – Africa, South America, and Australia –they found that the documentation of observed changes in physical and biological systems is still sparse despite warming trends attributable to human causes.

The authors concluded that environmental systems in these continents need to be better studied especially in tropical and subtropical areas where there is a general lack of data and published studies.

“It was a real challenge to separate the influence of human-caused temperature increases from natural climate variations or other confounding factors, such as land-use change or pollution” added Professor Karoly.

“This was only possible through the combined efforts of our multi-disciplinary team, which examined observed changes in many different systems around the globe, as well as global climate model simulations of temperature changes."

“Humans are influencing climate through increasing greenhouse gas emissions and the warming world is causing impacts on physical and biological systems that are now attributable at the global scale and in North America, Asia, and Europe” said Dr Cynthia Rosenzweig at NASA GISS in New York, the paper’s lead author.