Global warming: impacts of temperature increases

The Intergovernmental Panel on Climate Change (IPCC) will publish a report, the most complete overview of climate change science, in Paris on February 2. It will guide policy makers combating global warming.

A draft of the report projects temperatures rising by 2 to 4.5 Celsius (3.6 to 8.1 Fahrenheit) above pre-industrial levels by 2100, with a "best estimate" of a 3C (5.4 F) rise.

Below are some estimates of the global implications of different temperature rises relative to pre-industrial levels, as detailed in a report on climate change by Nicholas Stern, chief British government economist, published in October.

Temp. rise/ Impacts 1 DEGREE

* Shrinking glaciers threaten water for 50 million people

* Modest increases in cereal yields in temperate regions

* At least 300,000 people each year die from malaria, malnutrition and other climate-related diseases

* Reduction in winter mortality in higher latitudes

* 80 percent bleaching of coral reefs, e.g. Great Barrier Reef

2 DEGREES

* 5 - 10 percent decline in crop yield in tropical Africa

* 40 - 60 million more people exposed to malaria in Africa

* Up to 10 million more people affected by coastal flooding

* 15 - 40 percent of species face extinction (one estimate)

* High risk of extinction of Arctic species, e.g. polar bear

* Potential for Greenland ice sheet to start to melt irreversibly, committing world to 7 meter sea level rise

3 DEGREES

* In Southern Europe, serious droughts once every 10 years

* 1 - 4 billion more people suffer water shortages

* Some 150 - 550 additional millions at risk of hunger

* 1 - 3 million more people die from malnutrition

* Onset of Amazon forest collapse (some models only)

* Rising risk of collapse of West Antarctic Ice Sheet

* Rising risk of collapse of Atlantic Conveyor of warm water

* Rising risk of abrupt changes to the monsoon

4 DEGREES

* Agricultural yields decline by 15 - 35 percent in Africa

* Up to 80 million more people exposed to malaria in Africa

* Loss of around half Arctic tundra

5 DEGREES

* Possible disappearance of large glaciers in Himalayas, affecting one-quarter of China's population, many in India

* Continued increase in ocean acidity seriously disrupting marine ecosystems and possibly fish stocks

* Sea level rise threatens small islands, coastal areas