The overnight transformation of Sir Nicholas Stern from grey bureaucrat to green crusader would do a chameleon proud. Until this week, few people would have been able to name the British Treasury's bespectacled and unassuming chief economist. But the stark warnings contained in his eponymous report have thrust Sir Nicholas into the forefront of the international debate on climate change. The Stern Review examines the evidence for global warming, assesses its potential impact on society, and sets out a strategy for tackling the problem. So far, so predictable. But what sets the report apart from previous studies is its calculation that climate change will cost the global economy a whopping GBP3.68 trillion (HK$54.34 trillion) if 1 per cent of world gross domestic product is not spent now on reducing damaging carbon emissions. That his dire warnings have been taken so seriously is testament to 60-year-old Sir Nicholas' academic pedigree. The author of a long list of textbooks dealing with developing economies, he graduated with a mathematics degree from Cambridge and a degree in economics from Oxford in the 1960s. He devoted more than 20 years to research and teaching posts - in Britain, the US, France, India and in China, at the People's University of China in Beijing - before becoming one of the foremost economic policy-makers of his generation. Sir Nicholas was plucked from the halls of academia in 1994 and appointed chief economist of the European Bank for Reconstruction and Development in London, a position he held until 2000, when he moved to Washington to take on the same job at the World Bank. He was lured away from Washington in 2003 by Britain's prime minister-in-waiting, Chancellor Gordon Brown, to take up his present role at the treasury. His behind-the-scenes contribution to policy-making was recognised in 2004, when a knighthood was bestowed on him for his services to economics. This week's climate change report was the second ambitious review the chancellor had commissioned Sir Nicholas to produce. Last year he published the findings of the Commission for Africa, which led to commitments by the Group of Eight leaders at their Gleneagles Summit to tackle third world poverty. Little is known about Sir Nicholas' personal life or views. Inquiries made about his early years and family were politely but firmly batted away this week by his colleagues at the treasury. What is known is that the married father of three is an avid sports fan and a founding member of minor league English soccer club AFC Wimbledon. His area of academic expertise and work on Oxfam and United Nations committees point to a keen social conscience. He spent eight months living in a remote Indian village in the 1970s while writing a book on the country's development, and has been reported in the British press recently as being unhappy with the adverse impact on poor nations of the World Bank's moves to crack down on corruption. Sir Nicholas is also known as a fearless number cruncher who comes up with economic solutions that do not always fit the policy framework of his political masters. But he is one of Mr Brown's closest advisers and his apocalyptic environmental scenario is widely seen as tailor-made for the chancellor to introduce an array of green taxes to a British voting public that is keen to save the planet but less keen on paying for the privilege. However, the target of the 575-page Stern Review extends far beyond the deep pockets of British taxpayers. Britain produces just 2 per cent of the world's carbon output while the world's biggest polluter - the US, which accounts for 20.6 per cent of emissions - remains unconvinced of the need for immediate action. Meanwhile, China - the world's second-worst polluter accounting for 14.8 per cent of emissions - has its own problems juggling runaway development with a growing awareness of its wider environmental responsibilities. British Prime Minister Tony Blair this week said the report represented 'the final piece of the jigsaw to convince every single leader, including those in America, China and India, that this must be top of their agenda'. Sir Nicholas sets out a four-point plan to redress the ecological balance: reducing demand for emission-producing goods and services, stemming deforestation, increasing efficiency, and adopting lower-carbon technology for heat, energy and transportation. 'Our actions over the coming few decades could create risks of major disruption to economic and social activity, later this century and in the next, on a scale similar to those associated with the great wars and the economic depression of the first half of the 20th century,' the report says. However, it adds: 'There is still time to avoid the worst impacts of climate change, if we act now and act internationally. 'Strong, deliberate policy choices by governments are essential to motivate change. But the task is urgent. Delaying action, even by a decade or two, will take us into dangerous territory. We must not let this window of opportunity close.'