Sydney, Sep 11 - Scientists have sounded the alarm bells over impending global catastrophe as existing governments and institutions are too powerless to head it off.

The world faces a compounding series of crises - from energy, food shortages, to climate change, to new diseases and increasing anti-biotic resistance - all driven by human activity, which is beyond the capacity of existing institutions to cope with, warns a group of eminent environmental scientists and economists.

There are few institutional structures to achieve co-operation globally on the sort of scales now essential to avoid very serious consequences, warns lead author Brian Walker of the Commonwealth Scientific and Industrial Research Organisation (CSIRO), on the occasion of the eighth anniversary of the 9/11 in the US.

'Energy, food and water crises, climate disruption, declining fisheries, ocean acidification, emerging diseases and increasing antibiotic resistance are examples of serious, intertwined global-scale challenges spawned by the accelerating scale of human activity,' say researchers from Australia, Sweden, the US, India, Greece and The Netherlands.

While there are signs of emerging global action on issues such as climate change, there is widespread inaction on others, such as the destruction of the world's forests to grow biofuels or the emergence of pandemic flu through lack of appropriate animal husbandry protocols where people, pigs and birds co-mingle.