London: Global warming is expected to take an increasing toll on the economy, food production, fresh water supplies and human health as the century progresses, according to a draft study for the United Nations.
A temperature increase of 2.5 degrees Celsius (4.5 degrees Fahrenheit) since industrialization may lead to losses of as much as 2% of global economic output, an analysis by the UNís Intergovernmental Panel on Climate Change showed. Temperatures have already risen by about 0.8 degrees.
The document, posted on the No Frakking Consensus blog, charts declining crop yields, increased coastal flooding and the migration of species toward the poles as the planet warms. Itís the second of three reports by the panel designed to inform lawmakers worldwide as they work toward a global treaty and devise domestic policies to cut greenhouse gases and protect against the effects of climate change.
Observed impacts of climate change are widespread and consequential, the researchers wrote. Recent changes in climate have caused impacts on natural and human systems on all continents and across the oceans.
The draft document, on impacts, adaptation and vulnerability due to climate change, is dated 28 October, and will be revised line-by-line by representatives of governments around the world at a meeting in Yokohama, Japan, from 25 March to 29 March.
The No Frakking Consensus blog, which uses the strap line Climate scepticism is free speech, is written by Donna Laframboise, a Canadian journalist who has authored a collection of essays critical of IPCC chairman Rajendra Pachauri.
ďThe IPCC believes this document should remain secret,Ē Laframboise wrote. ďI think the public has a right to examine it. Itís important to be able to compare what IPCC personnel have written in this draft to what the final, non-draft version will say when itís released to much fanfare next March.Ē
Jonathan Lynn, a spokesman for the panel, confirmed in an email that the final draft was sent to governments on 28 October. He declined to comment on its contents.
ďThis report is still a work in progress, so we donít have anything to say,Ē Lynn said. ďItís likely to undergo further changes in the approval plenary in March.Ē
The document says that climate change will reduce median crop yields by as much as 2% a decade for the rest of the century, compared to a baseline that assumes no warming. Tropical countries face the greatest risks, it said. At the same time, the researchers project crop demand to increase by 14% a decade through 2050.
The assessment is more alarming than the panelís report in 2007, which projected global food production to increase for temperature rises of 1 degree to 3 degrees.
Negative impacts of climate change on crop and terrestrial food production have been more common than positive impacts, the researchers said. Recent periods of rapid food and cereal price increases have indicated that current markets in key producing regions are sensitive to climate extremes.
Local temperature increases of a degree or more above pre-industrial levels are predicted to reduce yields of wheat, rice and corn in both tropical and temperate regions, with some more localized areas benefiting, according to the study.
Climate change is likely already harming human health, according to the paper. The researchers say with very high confidence that warming will worsen existing health problems between now and mid-century, and they have high confidence that it will increase ill-health in many regions through 2100, compared with a scenario without warming.
There will be a greater likelihood of injury, disease and death due to more intense heat waves and fires, a bigger chance of under-nutrition due to diminished food production, and increased risks of catching food- and water-borne diseases, according to the study. At the same time, there will be modest improvements in cold-related deaths.
The economic cost of warming of 2.5 degrees from pre-industrial levels may range from 0.2% to 2% of global output, according to the study. Little is known about the total cost of impacts above 3 degrees of warming, it said.
Throughout the 21st century, climate change impacts will slow down economic growth and poverty reduction, further erode food security and trigger new poverty traps, the latter particularly in urban areas and emerging hotspots of hunger.
In the UNís last summary report in 2007, researchers said 4 degrees of warming could cost the global economy 1% to 5% of output. They were less precise on costs associated with lower levels of warming that are more likely in the nearer term.
The report on impacts is the second in a trilogy of reports planned by the panel. The IPCC in September published a synopsis of the already observed physical changes in the Earthís climate, and in April will publish a third study examining the tools we have to fight climate change. An overarching summary is due for publication in October.
Other findings of the document include:
Climate change will indirectly increase risks of violent conflict due to civil war, inter-group violence and violent protests as resources become scarcer.
By 2100, hundreds of millions of people may be affected by coastal flooding due to climate change and development patterns that donít take into account the need for adaptation.
Animal and plant species are shifting their ranges and seasonal activities in response to warming temperatures. the tropics are likely to lose species diversity as creatures move their ranges away from the Equator.
A large fraction of land and freshwater species face increased risk of extinction at projected rates of warming.
At higher projected rates of warming, areas such as the tundra and the Amazon rainforest face a high risk of abrupt and irreversible changes in their ecosystems.
Climate change will cut available freshwater significantly in most dry subtropical regions.
Governments arenít standing still. Most national governments in Africa are starting efforts to adapt their economies and peoples to the changing climate. In Australasia, planning for sea-level rise is widespread, and local governments in North America are adapting public infrastructure to better cope with impacts.