There is already so much excess carbon dioxide (CO2) in the atmosphere from our burning of fossil fuels that temperatures will rise and the climate change faster than at any other time in our history. This will have potentially devastating impacts. Sea level is set to rise for another 800 years as ice caps and glaciers melt and the oceans expand with the increased warmth. The debate among scientists is not whether climate change is happening, but how quickly it will happen, how bad its effects will be and what nasty surprises it holds in store. There are still those that say there is plenty of time to react, but there is increasing evidence that unless action is taken quickly global warming may run out of control. For civilisation to survive and prosper, action is essential.

"Climate change is the biggest challenge that we face in the world today. It is already leading to significant changes in the world's physical environment. Extreme weather events are becoming more frequent. Glaciers are melting. Sea ice and snow cover are declining. Animals and plants are responding to an earlier spring. Global warming has already driven up mean sea levels by 10-20 centimetres (4-8 inches) during the last 100 years, and this is forecast to rise by up to another 88 centimetres (35 inches) by 2100. It is a sobering fact that around 100 million people globally live less than 88 centimetres above sea level."

"By the end of this century, our planet may look very different from how it does today. Many small island nations might no longer exist, inundation of coastal areas could lead to the displacement of hundreds of millions of people, and former agricultural lands could become unable to support crops. While all countries are vulnerable to the consequences, developing countries are especially at risk. Their economies will suffer most from the heightened frequency of extreme droughts, floods and storms associated with climate change. There is a real risk that climate change could undermine human development. We must not let that happen."

"Throughout history, human beings understood that they were utterly dependent on nature. People knew that in this world everything is interconnected and thus, every action has repercussions and responsibilities. Over the past century, that sense has been shattered so we no longer see it with clarity. Today, we buy tropical food in winter without asking about the environmental effects of shipping it halfway around the planet; we buy clothes without asking where the materials were grown and under what conditions; we rush asthmatic children to hospitals in SUVs without linking our lifestyles with the respiratory crisis. We acknowledge climate change but turn a blind eye to the way it's altering our fragile ecosystems."

"Climate change is a subtle form of human rights violation. There is no direct persecution or threat, but combustion of fossil fuels in industrialised nations has jeopardised the ability of certain societies to maintain their traditional practices, diminishing their cultural identity and their connection with their natural environment. In 1998, the Intergovernmental Panel on Climate Change recognised that global warming could lead to a wave of environmental refugees: some suggest as many as 150 million by 2050."

"The Asian tsunami of December 2004 was one of the worst natural disasters of our lifetime. More often, disasters are man-made, a result of conflict or climate change. And it is most often poor people who are on the frontline of climate change. In a world where population is set to increase to around nine billion by 2050, the challenge of meeting food and water needs and rights is going to be monumental. By reducing our own greenhouse gas emissions we can push the climate change frontline back – and not wait for it to come knocking on our own doors."

"The interactions between climate and health are complex, and we can make only approximate estimates of the extent to which global climate change has affected disease in the past, or will do in the future. But our current knowledge suggests that climatic changes since the 1970s may already be causing over 150,000 deaths annually and that if left unmitigated, greenhouse gas emissions will increase disease burdens in the coming decades. This does not mean that we are powerless to respond. Choosing sustainable development paths can help protect us from the effects of a changing climate, while simultaneously addressing many of our greatest current health concerns."

"The most severe impacts of flooding and threats to public health from global climate change will be felt in our cities. Most dramatically of all, cities like New Orleans and Miami, or even parts of New York and Los Angeles, could end up routinely flooded. However, there are signs of hope, and cities are leading the way – Berlin, Los Angeles, Mexico City, London, Toronto, Melbourne, Portland and many others are instituting action plans to reduce their CO2 emissions. While our federal government fails to act in the United States, I urge individuals to ask their local leaders to purchase clean cars, build green facilities, and buy green power. Our actions may determine if we win or lose the war for a habitable planet."