Friday, February 02, 2007

"Global Warming Facts": Impact of Temperature Rises

This post brings together a series of facts about global warming from PlanetArk ahead of today's IPCC report.

1. The Impacts of Temperature Rises
2. Future Projections
3. UN Climate Panel and Past Reports

Global Warming: Impacts of Temperature Rises

The Intergovernmental Panel on Climate Change (IPCC) will publish a report, the most complete overview of climate change science, in Paris on Feb. 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 in degrees Celsius 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


* 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 metre sea level rise


* 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


* 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


* 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 such as Florida and major cities such as New York, London, and Tokyo

Future Projections:

Temperatures are likely to rise by 2-4.5 Celsius (3.6-8.1 Fahrenheit) above pre-industrial levels if carbon dioxide concentrations are kept at 550 parts per million in the atmosphere, against about 380 now. The "best estimate" for the rise is about 3C (5.4F).

- The warming is very unlikely to be less than 1.5C (2.7F). Rises much above 4.5C cannot be ruled out but those computer projections do not fit well with observations. Main uncertainties are whether more clouds will form in a warmer world -- and bounce heat back into space.

- The report cites six models with core projections of sea level rises ranging from 28 to 43 cms (11.0-16.9 inches) by 2100. That is a narrower and lower band than the 9 to 88 cms gain (3.5-34.6 inches) forecast in 2001.

- It is "very likely" that extremes such as heatwaves and heavy rains will become more frequent. Arctic sea ice could disappear in summer by the latter part of the 21st century in some projection. Warming is expected to be greatest over land and at high northern latitudes, and least over the Southern Ocean and North Atlantic.

- Antarctica is likely to stay too cold for wide surface melting and is expected to gain in mass due to more snow.

- A system of Atlantic currents including the Gulf Stream, bringing warm waters northwards, are very likely to slow by 2100 but an overall warming will more than offset any cooling effect. The draft says that an abrupt shift is "very unlikely".

UN Climate Panel and Past Reports

Following are some facts about the Intergovernmental Panel on Climate Change (IPCC):

- The IPCC was set up in 1988 by the United Nations to help policy makers address climate change. It draws on work by about 2,500 specialists in more than 130 countries.

- A draft of the new report, the IPCC's fourth assessment, says that it is "very likely" that human activities, led by burning fossil fuels, are the main cause of warming in the past 50 years. "Very likely" means more than 90 percent probability.

- The 2001 study said there was "new and stronger evidence" linking human activities to rising temperatures. It also said it was "likely" that human activities caused most of the warming in the last half century -- "likely" means at least a 66 percent chance.

- In 1995, the IPCC report concluded that "the balance of evidence suggests a discernible human influence on global climate". That report paved the way to the U.N.'s Kyoto Protocol in 1997, which obliges 35 industrial nations to cut greenhouse gases to 5 percent below 1990 levels by 2008-12.

- The first report in 1990 outlined risks of rising temperatures and played a role in prompting governments to agree a 1992 U.N. climate convention that set a non-binding goal of stabilising greenhouse gases at 1990 levels by 2000. That target was not met overall.

- Concentrations of heat-trapping greenhouse gases in the atmosphere, largely from burning fossil fuels in power plants, factories and vehicles, have risen by more a third since before the Industrial Revolution.

- Temperatures rose by about 0.6 Celsius (1.1 Fahrenheit) during the 20th century. The 10 warmest years since records began in the 1850s have been since 1994.

- Rising temperatures are likely to cause more floods, erosion, desertification, heatwaves, drive many species to extinction and raise global sea levels. Benefits in some regions may include longer growing seasons.

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