Global Warming

Greenhouse Gases

Ice Melting

"This is the largest single event in a series of retreats by ice shelves in the Peninsula over the last 30 years. The retreats are attributed to a strong climate warming in the region. The rate of warming is approximately 0.5 degrees Celsius per decade, and the trend has been present since at least the late 1940s. Overall in the Peninsula, extent of seven ice shelves has declined by a total of about 13,500 km2 since 1974. This value excludes areas that would be expected to calve under stable conditions."

Glaciers are large masses of ice which form in areas of high snowfall and cool temperatures, even in summer. Glaciers are located in Antarctica, or at high altitudes on the slopes of large mountains (Alpine Glaciers).

"A glacier is maintained by accumulation of snow at high altitudes, balanced by melting at low altitudes or discharge into the sea." (19)

Alpine glaciers are particularly susceptible to shifts in climate and respond to long term changes in the Earth’s climate. As the temperature of the Earth increases the melting at the base of the glacier happens faster than the speed at which it moves down the slope or valley. (20)

Once a glacier has disappeared altogether, there is far less melt-water. Currently, millions of people around the world rely in part, or completely on rivers fed by glaciers.

Atmospheric radiator

The key is the Gulf Stream. After it emerges from the Caribbean, it splits in two, with one part heading north-east to Europe and the other circulating back through the tropical Atlantic.

As the north-eastern branch flows, it gives off heat to the atmosphere, which in turn warms European land.

"It's like a radiator giving its heat to the atmosphere," said Harry Bryden from the National Oceanography Centre (NOC) at Britain's Southampton University. "The heat it gives off is roughly equivalent to the output of a million power stations," he told reporters.

By the time it reaches the northern latitudes around Greenland and Iceland, the water has cooled so much that it sinks towards the ocean floor, a process known as "overturning". This cooler water heads south, forming the return stream of a conveyor belt. The complete cycle sees warm water coming northwards on the ocean's surface, and the cold water returning hundreds or thousands of metres underwater.

Florida-based scientists monitor the northwards-flowing Gulf Stream, and have found it has remained roughly constant over the last 50 years. The NOC researchers concentrated on the colder water flowing south; and they found that over the last half century, these currents have changed markedly.

"We saw a 30% decline in the southwards flow of deep cold water," said Harry Bryden. "And so the summary is that in 2004, we have a larger circulating current [in the tropical Atlantic] and less overturning." And less heat then delivered to European shores.

First evidence

Computer models of climate have regularly predicted that the North Atlantic conveyor may well reduce in intensity or even turn off altogether, a concept that was pushed beyond credence in the Hollywood blockbuster The Day After Tomorrow.

What happens is that as Arctic ice melts and Arctic rivers flow faster - trends which have both been documented - the northern oceans become less saline. Less salinity means a lower density; the waters then cannot sink, so the conveyor weakens.

Computer models have predicted that if it turned off completely, Europe would cool by perhaps four to six degrees Celsius. Commenting in Nature, Detlef Quadfasel from the University of Hamburg writes that the NOC experiments provide "...the first observational evidence that such a decrease of the oceanic overturning circulation is well underway."

Source

Global Mean Temperature

Change (°C) (a)

Atmospheric CO2 Stabilisation Level (ppmv)

Azar and Rodhe (1997) (4) 1.4 375

Climate Options for the Long-Term (2002) (5) 1.5 450

Climate Taskforce (2005) (6) 1.4 400

Environmental Systems Analysis Group (2005) (7) 0.9

European Climate Forum (2004) (8) 1.9 (b)

European Union (1996) (9) 1.4 550

Hansen et al. (2005) (10) 1.0 475

Klimatkommittén (2000) (11) 550

Mastrandrea and Schneider (2004) (12) 2.9 (c)

O’Neill and Oppenheimer (2002) (13) 2.0 450

Rijsberman and Swart (1990) (14) 1.4

Royal Commission on Environmental Pollution (2003) (15) 550

Wissenschaftlicher Beirat der Bundesregierung (1995) (16) 1.3

Wissenschaftlicher Beirat der Bundesregierung (2003) (17) 1.4

Average 1.5 475

Table notes: (a) Relative to 1990, assuming 0.6°C of warming occurred between the industrial revolution and 1990 (b) "Critical limits" estimated as 1.4-2.5°C; midpoint of this range used here (c) Median estimate of the threshold for "dangerous anthropogenic interference"

Carbon Offset

Some things that we do cause carbon dioxide to be made and there is nothing we can do about it. An example of this is travelling by aeroplane. To make up for this, we can buy a carbon offset.

For example, to carbon offset a flight between Sydney and Melbourne, you could pay a company $8 to plant trees which will absorb the carbon dioxide your flight made.

This means that your travel has become carbon neutral.

DID YOU KNOW? A standard compact fluorescent lamp saves about 750 kgs of greenhouse gas and $45 over its lifetime.

Save Earth by:

Electric Vehicles

Hybrid Vehicles

Global Warming Health Threats Global warming is already affecting human health around the world. The impact will be widespread, and plans to cope are needed now.

HOTSPOTS

Click on the map to view examples of health hotspots and preparedness plans.

HEALTH IMPACTS Global warming affects human health worldwide, from diminished air quality to degraded food and water supplies to catastrophic weather events.

The Consequences of Global Warming On Glaciers and Sea Levels Arctic summers could be ice-free by 2040, and sea levels could rise as much as 23 inches by 2100 if current warming patterns continue.

Melting Glaciers, Early Ice Thaw Rising global temperatures will speed the melting of glaciers and ice caps and cause early ice thaw on rivers and lakes.

Warning signs today:

After existing for many millennia, the northern section of the Larsen B ice shelf in Antarctica -- a section larger than the state of Rhode Island -- collapsed between January and March 2002, disintegrating at a rate that astonished scientists. Since 1995, the ice shelf's area has shrunk by 40 percent.

According to NASA, the polar ice cap is now melting at the alarming rate of nine percent per decade. Arctic ice thickness has decreased 40 percent since the 1960s.

Arctic sea ice extent set an all-time record low in September 2007, with almost half a million square miles less ice than the previous record set in September 2005, according to the National Snow and Ice Data Center. Over the past 3 decades, more than a million square miles of perennial sea ice -- an area the size of Norway, Denmark and Sweden combined -- has disappeared.

The Consequences of Global Warming On Wildlife Rising temperatures ravage coral reefs and melt the habitats of polar bears and Antarctic penguins.

Ecosystem Shifts and Species Die-Off Increasing global temperatures are expected to disrupt ecosystems, pushing to extinction those species that cannot adapt. The first comprehensive assessment of the extinction risk from global warming found that more than 1 million species could be obliterated by 2050 if the current trajectory continues.

The Consequences of Global Warming On Health

Hotter weather enables deadly mosquitoes to travel greater distances; carbon dioxide in the air aggravates asthma and allergies.

Deadly Heat Waves More frequent and severe heat waves will result in a greater number of heat-related deaths.

The Consequences of Global Warming On Weather Patterns Higher temperatures could lead to increased droughts and wildfires, heavier rainfall and a greater number of Category 4 and 5 hurricanes.

More Powerful and Dangerous Hurricanes Warmer water in the oceans pumps more energy into tropical storms, making them stronger and potentially more destructive.

Global Warming is an International Issue

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Attributed and expected effects Environmental Main articles: Effects of global warming and Regional effects of global warming

Mitigation Main article: Mitigation of global warming

Debate and skepticism Main articles: Global warming controversy and Politics of global warming See also: Scientific opinion on climate change, Climate change consensus, and Climate change denial

Per capita greenhouse gas emissions in 2000, including land-use change.

Per country greenhouse gas emissions in 2000, including land-use change.

Economic Main articles: Economics of global warming and Low-carbon economy

Projected temperature increase for a range of stabilization scenarios (the colored bands). The black line in middle of the shaded area indicates 'best estimates'; the red and the blue lines the likely limits. From IPCC AR4.

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Made by: Sahil Raj