Mark Lynas is a journalist and a campaigner specializing in climate change. He spent the last three years travelling and investigating the impact of global warming worldwide. In his book High Tide: News from a Warming World Mark documents the devastation he's seen on his travels; from melting glaciers in Peru, to the emergence of new deserts in China. He insists global warming is a reality.

Increasing sea levels are threatening the very survival of some small islands across the globe. Tuvalu is under threat, one of many Pacific Islands facing climate change disaster as a result of sea level rise. These Pacific islands openly and continuously criticized the industrial nations for failure to take definitive steps to reduce pollution of the global atmosphere.

The Big Question visits Belize, where any rise in sea levels of the magnitude projected by the IPCC would put 90% of the country's beaches under water, create havoc on the barrier reef, and affect agricultural production and drinking water supplies. Carlos Fuller is the chief meteorologist and coordinator of the Belize Climate Change Project. He blames the rich nations of the world because they are the biggest emitters of greenhouse gases, which heat up the earth.

So what's being done to stop or slow down emissions of one of those greenhouse gases? In 1997 governments from around the world gathered in the Japanese city of Kyoto, and drafted what's known as the Kyoto Protocol. The terms of the Kyoto protocol commits industrialised nations to reduce their emissions of six greenhouse gases by an average of 5.2% from their 1990 levels within a decade. Scientists say it would take carbon cuts of 60% or more to prevent dangerous climatic instability, so Kyoto would be only a modest though necessary start.

So does a warmer world mean a sicker world? Sari Kovats is an epidemiologist at the London School of Hygiene and Tropical Medicine. She says global warming creates the ideal conditions for the spread of infectious diseases like malaria. The World Health Organisation is warning that not only could fresh water supplies be jeopardised, but disasters like floods and droughts could lead to an increase in other diseases.

But global warming can also have positive effects, since higher temperatures and higher carbon dioxide concentrations improve the ecosystem's productivity. David Westphal runs Penshurst Vineyards in Kent, in the South East of England. David set up his vineyard back in 1971. He says as the weather gradually became warmer, he's been able to grow varieties of grapes like Chardonnay and Pinot Noir - varieties that used to thrive only in countries with warmer climates. He says the quality of wine produced in England now is on a par with Australian, and even French, wine.

This edition of The Big Question was first broadcast on 31st July 2004

The BBC and the Open University are not responsible for the content of external websites