A report by the United Nations’ International Panel on Climate Change -- the most authoritative voice on global warming -- released in November, contains chilling warnings for the world.

 The report establishes that the amount of greenhouse gas atmosphere is already above the threshold that could potentially cause dangerous climate change.

 “We've all been hoping that we can avoid dangerous climate change," Australian environmentalist Tim Flannery told the ABC.

 "But this report means that we already stand an acceptable risk of dangerous climate change, and the need for action is even more urgent”.

 “As of mid 2005, there was about 455 parts per million of what's called carbon dioxide equivalent. And that's a figure that's gathered by taking the potential of all of the 30 greenhouse gases and converting them into carbon dioxide potential, so we call it CO2 equivalent.

 “We thought we'd be at that threshold within about a decade, we thought we had that much time. But the new data indicates that in about mid 2005 we crossed that threshold".

 The IPCC was established in 1988 by two United Nations organizations, the World Meteorological Organization (WMO) and the United Nations Environment Program (UNEP), to evaluate the risk of climate change brought on by humans.

 In a report released in May this year, the IPCC said that "there is international scientific consensus that climate change is happening, it is caused by human beings; it is "very likely due to an increase in greenhouse gases concentrations and its effects can and should be mitigated. (IPCC, May 2007, Working Group III, Fourth Assessmant Report).

Scientists agree that since the start of the 20th century, the global average surface temperature has risen between 0.6 degrees C and 0.7 degrees C. (Stronger Evidence but New Challenges, Climate Change Science 2001-2005) .

The fourth Global Environment Outlook (GEO-4), published by the United Nations Environment Program (UNEP) warns that climate is changing faster than at any time in the past 500,000 years.

The 570 page report, which was compiled by 390 experts from observations, studies and data garnered over two decades, says global average temperatures are forecast to rise by 1.8 to four degrees celsius by 2100.

Observable changes

It has been observed a decrease of Artic sea ice cover from the 70s to present, and the Artic Climate Impact Assessment 2004 says the artic ocean could be nearly completed or totally ice-free during the summer months by the end of this century.

The European Space Agency says nearly 200 satellite photos taken together in September 2007 show an ice-free passage along northern Canada, Alaska and Greenland, and ice retreating to its lowest level since such images were first taken in 1978.

And this year the creators of the world-renowed Times Atlas, which is published every four years, said they had to drastically modify their edition, becasue of changes in the world's landscapes caused by global warming.

For example, map makers had to redraw costlines and reclassify types of land to reflect changes to geographical features like Lake Chad in Africa, which is now 95 per cent smaller than it was in 1963.

The IPCC says since 1993, the rate of sea level rise has increased to about 3 mm per year, and during the past 100 years sea level has risen 10-20 cm.

Visible effects of global warming worldwide are the increased frequency and intensity of heatwaves, droughts, storms, floods and cyclones. (Climate change in Australia: technical report 2007, CSIRO)

Oxfam says the number of disasters reported globally during 2000-2004 was 55 per cent higher than during 1995-1999 and affected one third more people.

 Temperature and carbon dioxide

 

The IPCC says it is “very likely” (90%) that human activities are causing global warming.

The IPCC claims that a registered temperature increase since the start of the 20th century coincide with an increase in greenhouse gas emissions.

Levels of carbon dioxide in the atmosphere increased significantly since the beginning of the industrial revolution, 250 years ago. And between 1970 and 2004 global greenhouse gas emissions have increased by 70%.

Human activities such as burning fossil fuels (coal, oil and natural gas), agriculture and land clearing, are generating more greenhouse gases. Greater concentrations of greenhouse gases trap more heat and raise the Earth’s temperature, in what is called the greenhouse effect.

Ice core records that go back 420,000 years show that carbon dioxide levels in the atmosphere varied between 180 and 280 parts per million (ppm) due to glacial cycles. But currently, carbon dioxide levels are 430 ppm.

The IPCC says with current climate change mitigation policies and related sustainable development practices, global GHG emissions will continue to grow over the next to decades, as well as the Earth’s temperature.

But hasn’t it happened before?

Throughout history, the Earth has experienced cold and warm periods, known as ice ages and interglacial periods. But scientists claim the current rate and magnitude of warming are significant in the context of the last 400,000 years.

Scientist say even a warming of 1-2 degrees C could challenge the adaptive capacity of a range of human and natural systems.

The Australian Greenhouse Office says even the 0.6 degrees C warming over the last 100 years has been associated with increasing heat waves and floods, more intense droughts, retreat of glaciers, coral bleaching, and shifts in ecosystems.

 

 

Oceans and forests are losing ability to absorb CO2

A study published in the Proceedings of the National Academy of  Sciences in the United States, conducted mainly by IPCC members, says carbon dioxide in the atmosphere is increasing much faster than expected, as trees and oceans struggle to absorb the greenhouse gas

"Atmospheric carbon dioxide growth has increased 35 percent faster than expected since 2000," said a statement from The British Antarctic Survey (BAS), one of the bodies involved in the research.

 
Inefficient use of fuels increased CO2 by 17 percent, while the other 18 percent was due to a decline in the efficiency of natural "sinks," the forests and seas that soak up the gas from the atmosphere, it said.

"Fifty years ago, for every tonne of CO2 emitted, 600 kilograms were removed by natural sinks. In 2006 only 550 kilograms were removed per tonne and that amount is falling," said the study's lead author, Pep Canadell of the Global Carbon Project, in a statement.

The finding touches on a key aspect of the global warming question, because for decades the ocean has been absorbing much of the CO2 released into the atmosphere from the burning of fossil fuels.

Research last year pointed to rising acidification of the oceans as a result of CO2 uptake, highlighting the risk of carbon saturation as well as a looming peril for biodiversity.

Methane and Nitrous Oxide

While carbon dioxide is blamed for 75 per cent of the greenhouse gases in the atmosphere, the remaining 25% is due to other gases, and as methan and nitrous oxide.

Large amounts of methane are released by cattle farming, waste dumps, rice farming and the production of oil and gas. Methane is in fact produced naturally when vegetation is burned, digested or rotted without the presence of oxygen.

And nitrous oxide, which has a global warming potential 310 times that of carbon dioxide, is released by chemical fertilizers and by burning fossil fuels.

The Report "The Physiscal Science Basis", released by IPCC's Working Group One in February 2007, has predicted that if global emissions of greenhouse gases continue to rise as projected, the average global temperatures will increase by up to 4 degrees C by 2100.

Predicted impacts

Health (Using climate to predict disease outbreaks, World Health Organisation 2004)
Increasing burden from malnutrition, diarrhoeal, cardio-respiratory and infectious disease.
Increased morbidity and mortality from heatwaves, floods and droughts.
Changed distribution of some disease vectors.
Substantial burden on health services.

Water
Decreasing water availability and increasing drought in mid-latitudes and semi-arid latitudes.
Hundreds of millions of people exposed to increased water stress.