The dangers of climate change

Hundreds of thousands were affected by flooding in Mozambique

Global warming may have played a part in floods in India that have destroyed the homes of millions of people and claimed hundreds of lives.

The devastating floods were triggered by heavy monsoon rains, which caused the Brahmaputra river and its tributaries to burst their banks.

India's Assam region has been badly hit

This is the second flood disaster in east India in two years; last year 30,000 people died after a massive cyclone hit the east Indian state of Orissa.

The past month has also seen lethal floods in China, Brazil and Russia. And earlier this year hundreds of thousands of people were stranded by floods that killed 48 people in Mozambique.

El Nino

At the same time, east Africa and Ethiopia are struggling through one of the worst droughts in living memory.

Bizarre global weather over the past two years has fuelled speculation that global warming is beginning to destabilise the Earth's climate.

A recent report by the United Nations Environment Programme, or Unep, said there was "little doubt that climate change is a major factor in making natural disasters nightly news".

But there are other factors involved; massive deforestation in many parts of the world has made way for new human settlements in flood-prone areas.

There is also the influence of the El Nino effect, a periodic weather disturbance which can lead to hot, dry weather in one part of the world, and heavy downpours and floods in another.

While aid agencies like the International Red Cross accept that the causes for the latest floods in India may be the result of a combination of all these factors, they say governments need to do more to prepare for bizarre weather before, not after, it arrives.

No single event can be ascribed to global warming.

The human factor

Some researchers still doubt that human activities are inducing rapid climate change.

They highlight the inconsistencies between the temperature records taken at the Earth's surface, which show rapid warming over the last two decades, and the data produced by satellite and balloon studies.

These show little if any warming of the low to mid-troposphere - the atmospheric layer extending up to about 8km from the Earth's surface.

Climate models generally predict that temperatures should increase in the upper air as well as at the surface if increased concentrations of greenhouse gases are causing the warming seen at the surface.