A forthcoming United Nations report will warn climate change will displace hundreds of millions of people by the end of this century.
As a result this will increase the risk of violent conflict and wipe trillions of dollars off the global economy.
The second of three publications by the UN’s Intergovernmental Panel on Climate Change (IPCC), due to be made public at the end of this month, is the most comprehensive investigation into the impact of climate change ever undertaken.
A draft of the final version has been seen by Britain’s The Independent newspaper which says the warming climate will place the world under enormous strain, forcing mass migration, especially in Asia, and increasing the risk of violent conflict.
Based on thousands of peer-reviewed studies and put together by hundreds of respected scientists, the report predicts that climate change will reduce median crop yields by two per cent per decade for the rest of the century, at a time of rapidly growing demand for food.
This will in turn push up malnutrition in children by about a fifth, it predicts.
The Independent says the report also forecasts that the warming climate will take its toll on human health, pushing up the number of intense heatwaves and fires and increasing the risk from food and water-borne diseases.
Fairfax Media is Australia reports Macquarie University’s Professor Lesley Hughes, a lead author of the report, declined to comment on its contents but said scientists had increasing confidence the climate was shifting, both from research and a rise in observations of extreme events.
“The climate system is very different from what it was three or four decades ago,” Professor Hughes said, citing the incidence of heatwaves and droughts.
The summary of the report runs for 76 pages. It notes the number of papers on adaptation to climate change had doubled in the five years to 2010, adding to the material to be assessed by the report’s authors.
The report predicts that by the end of the century “hundreds of millions of people will be affected by coastal flooding and displaced due to land loss”.
The majority affected will be in East Asia, South-east Asia and South Asia. Rising sea levels mean coastal systems and low-lying areas will increasingly experience submergence, coastal flooding and coastal erosion.
Relatively low local temperature increases of 1.0°C or more above pre-industralised levels are projected to “negatively impact” yields of major crops such as wheat, rice and maize in tropical and temperate regions.
The report forecasts that climate change will reduce median yields by up to two per cent per decade for the rest of the century, against a backdrop of rising demand that is set to increase by 14 per cent per decade until 2050.
A global mean temperature increase of 2.5°C above pre-industrial levels may lead to global aggregate economic losses of between 0.2 and 2.0 per cent, the report warns.
Global GDP was US$71.8 trillion in 2012, meaning a two per cent reduction would wipe US$1.4trn off the world’s economic output that year.
Until mid-century, climate change will impact human health mainly by exacerbating problems that already exist, the report says.
Climate change over the 21st century will have a significant impact on forms of migration that compromise human security, the report states.
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or example, it indirectly increases the risks from violent conflict in the form of civil war, inter-group violence and violent protests by exacerbating well-established drivers of these conflicts such as poverty and economic shocks.
Small-island states and other places highly vulnerable to sea level rise face major challenges to their territorial integrity.
Some “transboundary” impacts of climate change; such as changes in sea ice, shared water resources and migration of fish stocks have the potential to increase rivalry among states.
The Independent says the draft of the report says, “freshwater-related risks of climate change increase significantly with increasing greenhouse gas emissions”.
It finds that climate change will “reduce renewable surface water and groundwater resources significantly in most dry subtropical regions”, exacerbating the competition for water.
