The huge impact of climate change will be laid bare at the end of this month when the UN publishes its most authoritative account so far into the misery likely to be inflicted by unchecked global warming.

According to a final draft version of the report, seen by The Independent, climate change is set to have a devastating impact on everything from human health, social stability and food security to the economy, ecosystems and water resources by the end of this century. 

Coastal systems and low-lying areas

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. 

Food security

Relatively low local temperature increases of 1C 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 2 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. 

Global economy

A global mean temperature increase of 2.5C 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 $71.8trn (43.1trn) in 2012, meaning a 2 per cent reduction would wipe $1.4trn off the world’s economic output that year. 

Human health

Until mid-century, climate change will impact human health mainly by exacerbating problems that already exist, the report says. Climate change will lead to increases in ill-health in many regions, with examples including a greater likelihood of injury, disease and death due to more intense heatwaves and fires; increased likelihood of under-nutrition; and increased risks from food and water-borne diseases. Without accelerated investment in planned adaptations, climate change by 2050 would increase the number of undernourished children under the age of 5 by 20-25 million globally, or by 17-22 per cent, it says. 

Human security

Climate change over the 21st century will have a significant impact on forms of migration that compromise human security, the report states. For 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. 

Freshwater resources

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. Terrestrial and freshwater species will also face an increased extinction risk under projected climate change during and beyond the 21st century.

– THE INDEPENDENT/NZ Herald