http://www.guardian.co.uk/environment/climatechange

Grim outlook for poor countries in climate report, David Adam, Peter Walker and Alison Benjamin September 18 2007

The Arctic is again highlighted as being among areas most at risk. Photograph: Corbis
The effects of climate change will be felt sooner than scientists realised and the world must learn to live with the effects, experts said today.

Professor Martin Parry, a climate scientist with the Met Office, said destructive changes in temperature, rainfall and agriculture were now forecast to occur several decades earlier than thought.

He said vulnerable people such as the old and poor would be the worst affected, and that world leaders had not yet accepted their countries would have to adapt to the likely consequences.

The professor was speaking in London at a meeting to launch the full report on the impacts of global warming by the UN's Intergovernmental Panel on Climate Change (IPCC).

The report – which had its executive summary released earlier this year – says hundreds of millions of people in developing nations will face natural disasters, water shortages and hunger due to the effects of climate change.

Today Professor Parry, co-chair of the IPCC working group that wrote the report, said: "We are all used to talking about these impacts coming in the lifetimes of our children and grandchildren. Now we know that it's us."

He said the international response to the problem had failed to grasp that serious consequences such as reduced crop yields and coastal flooding were now inevitable. "Mitigation has got all the attention but we cannot mitigate out of this problem. We now have a choice between a future with a damaged world or a severely damaged world."

Professor Martin Parry says the world must adapt to climate change Countries such as Britain need to focus on helping nations in the developing world cope with the predicted impacts, by helping them to introduce irrigation and water management technology, drought resistant crops and new building techniques.

Dr Rajendra Pachauri, chair of the IPCC, said: "Wheat production in India is already in decline, for no other reason than climate change."

The report says that "extreme weather events" are likely to become more intense and more frequent, while higher global temperatures could affect crops and water supplies and spread disease.

The effect on ecosystems could be equally severe, with up to 30% of plant and animal species at risk of extinction if the average rise in global temperatures exceeds 1.5-2.5C.

The 1,000-page document is part of the IPCC's fourth overall assessment of climate change, to be published in full later this year. It was put together by the so-called Working Group II, which examines global warming's impact on the environment and people.

The experts involved warn that the consequences of rising temperatures are already being felt on every continent, and sooner than expected. It is "probably too late" to avoid some impacts in developing countries because about 1C of warming is already in the climate system, they warn. If it is not kept below 2C – which "currently looks very unlikely to be achieved" – up to 3.2 billion people will face water shortages and up to 600 million will face hunger, they have predicted.

The trade and development minister, Gareth Thomas, told the launch of the report at the Royal Geographical Society: "Failing to tackle it [climate change] will lead to floods, droughts and natural disasters which can destroy poor people's lives as well as their livelihoods."

Professor Parry said today that he was pessimistic about the chances of keeping the increase in global average temperatures below 2C. "And it's evident from the work of the IPCC that even with a maximum of 2C we're not going to avoid some major impacts at the regional level."

In February the report of the IPCC's first working group, which looks at the scientific background of climate change, concluded that global warming was "very likely" – a probability of 90% or greater – to have been caused by human activity.

A report in May by the IPCC's Working Group III, which examines how climate change can be addressed, argued that devastating global warming can be avoided without excessive economic cost but only if the world begins acting immediately.

Today's report concludes that while the impact of a warmer globe will have mixed effects – for example, it notes that crop yields could increase in northern Europe – the overall impact will be deeply negative, particularly in Africa, in the so-called "mega-deltas" of south and east Asia, and on small islands and in polar regions.

By 2020, the report warns, up to 250 million Africans may be left short of water, while access to sufficient food is "projected to be severely compromised by climate variability and change".

"New studies confirm that Africa is one of the most vulnerable continents to climate variability and change because of multiple stresses and low adaptive capacity," says the document.