Climate change is already contributing to the deaths of nearly 400,000 people a year and costing the world more than US$1.2 trillion (HK$9.3 trillion), wiping 1.6 per cent annually from global GDP, according to a new study.
The effects are being felt most keenly, according to the research, in developing countries, where damage to agricultural production from extreme weather linked to climate change is contributing to deaths from malnutrition, poverty and their associated diseases.
Air pollution caused by the use of fossil fuels is also separately contributing to the deaths of at least 4.5 million people a year, the report found.
The 331-page study, published last week and entitled "Climate Vulnerability Monitor: A Guide to the Cold Calculus of A Hot Planet", was carried out by the DARA group, a non-governmental body from Europe, and the global Climate Vulnerable Forum.
It was written by more than 50 scientists, economists and policy experts, and commissioned by 20 governments.
By 2030, the researchers estimate, the cost of climate change and air pollution combined will rise to 3.2 per cent of global GDP, with the world's least developed countries forecast to bear the brunt, suffering losses of up to 11 per cent of their GDP.
Sheikh Hasina, prime minister of Bangladesh, said: "A one degree Celsius rise in temperature [temperatures have already risen by 0.7 of a degree globally since the end of the 19th century] is associated with 10 per cent productivity loss in farming.
"For us, it means losing about four million tonnes of food grain, amounting to about US$2.5 billion. That is about two per cent of our GDP. Adding up the damages to property and other losses, we are faced with a total loss of about three to four per cent of GDP. Without these losses, we could have easily secured much higher growth."
But major economies will also take a hit, as extremes of weather and the associated damage - droughts, floods and more severe storms - could wipe two per cent off the GDP of the US by 2030, while similar effects could cost China US$1.2 trillion within the same time.
While many governments have taken the view that climate change is a long-term problem, there is a growing belief that the effects are already being felt. Scientists have been alarmed by the increasingly rapid melting of Arctic sea ice, which reached a new record minimum this year.
And, if the melting continues at similar rates, it could be ice-free in summer by the end of the decade. Some research suggests this melting could be linked to cold, dull and rainy summers in parts of Europe - as has been the predominant summer weather in the UK for the past six years. In the US, this year's drought has raised food prices and in India the disruption to the monsoon has caused widespread damage to farms.
Connie Hedegaard, the European Union's climate chief, said extreme weather was becoming more common as the effects of climate change take hold. "Climate change and weather extremes are not about a distant future," she wrote in a commentary for the Guardian last week. "Formerly one-off extreme weather episodes seem to be becoming the new normal."
Michael Zammit Cutajar, former executive secretary of the UN Framework Convention on Climate Change, said: "Climate change is not a distant threat but a present danger. Its economic impact is already with us."