A range of different gases can act as greenhouse gases. The common denominator for them is that they can absorb heat (thermal infrared radiation), which is emitted from the earth, and re-emit it.
When the sun shines on the earth, about 70 percent of the energy gets through the atmosphere. The remainder is retained or reflected by, for example, clouds. It is mainly invisible light that gets through.
In the earth’s surface the light is retained and converted into heat, which is sent back into space in the form of thermal infrared radiation – in the same way as a bonfire emits radiant heat. A part of this heat does not escape from the atmosphere, but is retained by greenhouse gases such as CO2 and methane. The thermal radiation causes the gas molecules to vibrate with energy, until the energy is released and re-emitted as thermal radiation. In this way the atmosphere retains for a time a part of the energy the earth receives from the sun. This is the greenhouse effect.
The atmosphere consists mainly of nitrogen and oxygen. The molecules of these two gases are simple – they consist of only two atoms. They do not absorb thermal radiation and therefore they are not defined as greenhouse gases. Other molecules have a structure that can capture heat radiation.
The most significant greenhouse gas is water vapour. But water vapour stays in the atmosphere only very briefly, and the amount of water vapour in the atmosphere is affected by other greenhouse gases, because warmer air causes increased evaporation from the oceans in particular.
The discussion about the anthropogenic greenhouse effect is mostly concentrated on the so-called ”long-lived” greenhouse gases. The most important ones are CO2, methane, nitrous oxide and CFC gases. In total they account for more than 97 per cent of the direct effect of the long-lived gases on how much heat is retained in the atmosphere.
Sunday, August 30, 2009
What is the greenhouse effect and global warming?
The greenhouse effect is a natural mechanism that retains the heat emitted from the earth’s surface. The earth’s average temperature is at the moment around 14 degrees celsius (57 degrees fahrenheit). If the natural greenhouse effect did not exist, the average temperature would be around minus 19 degrees celsius (minus 2 degrees fahrenheit).The greenhouse effect is caused by a range of different gases in the earth’s atmosphere. Water vapour makes the most significant contribution to the greenhouse effect, followed by CO2. The atmospheric content of greenhouse gases – in particular CO2 – and the consequences for the climate are being discussed because the content of these gases in the atmosphere has risen precipitously in a period covering approximately the latest 250 years, and especially the last 50.
At present the concentration of CO2 in the atmosphere is about 385 ppm (parts per million). Before industrialization it was about 280 ppm. Analyses of air contained in ice from the Antarctic ice cap show that there is far more CO2 in the air today than at any time in the last 650,000 years.
The consequence is that the greenhouse effect is becoming stronger, and therefore the earth is becoming warmer. How much warmer has, however, been a matter of dispute. The most recent assessment report from the IPCC is from 2007. It concludes that the earth’s average temperature has risen by 0.74 degrees in the period from 1906 to 2005. The warming is stronger over land areas than over the sea, and accordingly it is strongest in the northern hemisphere. At the same time occurrences of heat waves and violent downpours have also increased, the oceans have risen, and the ice at the world’s poles and on its mountains has begun to melt. All of these effects are predictable in the event of global warming.
The IPCC’s most recent assessment report concludes that the average temperature will continue to rise, but that the extent and the duration of this rise, and the severity of its consequences, depend on how quickly and how effectively emissions of greenhouse gases can be restricted and, over time, reduced.
At present the concentration of CO2 in the atmosphere is about 385 ppm (parts per million). Before industrialization it was about 280 ppm. Analyses of air contained in ice from the Antarctic ice cap show that there is far more CO2 in the air today than at any time in the last 650,000 years.
The consequence is that the greenhouse effect is becoming stronger, and therefore the earth is becoming warmer. How much warmer has, however, been a matter of dispute. The most recent assessment report from the IPCC is from 2007. It concludes that the earth’s average temperature has risen by 0.74 degrees in the period from 1906 to 2005. The warming is stronger over land areas than over the sea, and accordingly it is strongest in the northern hemisphere. At the same time occurrences of heat waves and violent downpours have also increased, the oceans have risen, and the ice at the world’s poles and on its mountains has begun to melt. All of these effects are predictable in the event of global warming.
The IPCC’s most recent assessment report concludes that the average temperature will continue to rise, but that the extent and the duration of this rise, and the severity of its consequences, depend on how quickly and how effectively emissions of greenhouse gases can be restricted and, over time, reduced.
The relationship between the IPCC and the UNFCCC
There is a close relationship between the IPCC and the international efforts to fight global warming. The UN’s climate convention, the UNFCCC (United Nations Framework Convention on Climate Change), establishes the framework within which by far the largest part of the international cooperation on climate takes place.
It was the first assessment report from the IPCC that in 1990 was the catalyst for the arrival of climate on the political agenda. After merely two years the text for the climate convention was adopted in New York in May 1992. Later the same year the convention was signed by more than 150 countries at the UN's Conference on Environment and Development (UNCED) in Rio De Janeiro. The countries that have ratified the convention meet every year at the COP meetings (Conference of the Parties to the Convention).Because the IPCC’s reports have both scientific and political support, they are the foundation upon which the UNFCCC cooperation is based. In addition the IPCC is a UN agency, and the UNFCCC’s technical and scientific subsidiary body (SBSTA) can ask the IPCC for relevant studies in relation to the negotiations. Accordingly it is the IPCC that draws up guidelines for how the individual countries are to calculate their emissions of greenhouse gases.
It was the first assessment report from the IPCC that in 1990 was the catalyst for the arrival of climate on the political agenda. After merely two years the text for the climate convention was adopted in New York in May 1992. Later the same year the convention was signed by more than 150 countries at the UN's Conference on Environment and Development (UNCED) in Rio De Janeiro. The countries that have ratified the convention meet every year at the COP meetings (Conference of the Parties to the Convention).Because the IPCC’s reports have both scientific and political support, they are the foundation upon which the UNFCCC cooperation is based. In addition the IPCC is a UN agency, and the UNFCCC’s technical and scientific subsidiary body (SBSTA) can ask the IPCC for relevant studies in relation to the negotiations. Accordingly it is the IPCC that draws up guidelines for how the individual countries are to calculate their emissions of greenhouse gases.
UN Framework Convention on Climate Change (UNFCCC)
In 1990, the United Nations General Assembly decided to start work on a climate change convention. The endeavors led to 154 countries signing the United Nations Framework Climate Change Convention (UNFCCC) at the UN Summit in Rio de Janeiro in 1992. Since then, 192 countries including the USA have ratified the convention.
The goals of the climate change convention are to stabilize the amount of greenhouse gases in the atmosphere at a level that prevents dangerous man-made climate changes.
According to the objective paragraph, this stabilization must occur in such a way as to give ecosystems the opportunity to adapt naturally. This means that food safety must not be compromised, and that the potential to create sustainable social and economic development must not be endangered.
Each year, a Conference of the Parties is held, where the countries which have ratified the convention meet and discuss how the convention’s goals can be implemented in practice. One of the tools, which the parties have agreed upon, is the Kyoto Protocol.
The climate change convention is administered by the United Nations Climate Change Secretariat in Bonn. The secretariat’s tasks include monitoring the development in the individual countries’ CO2 emissions, as well as keeping watch on which countries ratify the Kyoto Protocol.
The goals of the climate change convention are to stabilize the amount of greenhouse gases in the atmosphere at a level that prevents dangerous man-made climate changes.
According to the objective paragraph, this stabilization must occur in such a way as to give ecosystems the opportunity to adapt naturally. This means that food safety must not be compromised, and that the potential to create sustainable social and economic development must not be endangered.
Each year, a Conference of the Parties is held, where the countries which have ratified the convention meet and discuss how the convention’s goals can be implemented in practice. One of the tools, which the parties have agreed upon, is the Kyoto Protocol.
The climate change convention is administered by the United Nations Climate Change Secretariat in Bonn. The secretariat’s tasks include monitoring the development in the individual countries’ CO2 emissions, as well as keeping watch on which countries ratify the Kyoto Protocol.
Intergovernmental Panel on Climate Change
IPCC (Intergovernmental Panel on Climate Change) was established in 1988 by the special UN organizations for environment (UNEP) and meteorology (WMO) following the Brundtland Report ”Our Common Future”.
The goal of IPCC is to use scientific literature to evaluate the extent and understanding of climate changes and their effects, as well as the potential to adapt to or counteract anticipated climate changes.
It is a key point that the work in the United Nations Climate Change Panel follows normal procedures for scientific publications, in particular the principle of peer review. The scientific authors of the IPCC reports are all selected for reasons of their scientific expertise.
The authors’ task is to collate and evaluate the knowledge that is available in international scientific, technical and socio-economic literature using traditional scientific methods and working principles. Then, the reports are sent to specialists for review, and in a second round to government representatives from the member countries of the organizations.
Thus there are over 1200 independent scientific authors and 2500 reviewers who have taken part in the preparation of the IPCC’s Fourth Assessment Report published in 2007.
IPCC's secretariat is based in Geneva and is organized into three working groups and one Task Force.
The first working group evaluates literature in natural science about climate and climate change. The second is concerned with the consequences of climate change, and the potential for adapting to them, while the third working group evaluates the potential for reducing the planet’s emissions of greenhouse gases, and thus limiting the climate changes. Finally, the Task Force is responsible for the National Greenhouse Gas Inventories Program.
IPCC has published four Assessment Reports (in 1990, 1995, 2001 and 2007). Each Assessment Report consists of contributions from the three working groups and a Synthesis Report.
The Fourth Assessment Report has contributed to both the public and politicians gaining increased awareness that climate changes are man-made and are happening faster than earlier assumed. The report shows that climate changes are a reality today, and that the main culprit is greenhouse gas emissions caused by man, and notably CO2 emissions
The goal of IPCC is to use scientific literature to evaluate the extent and understanding of climate changes and their effects, as well as the potential to adapt to or counteract anticipated climate changes.
It is a key point that the work in the United Nations Climate Change Panel follows normal procedures for scientific publications, in particular the principle of peer review. The scientific authors of the IPCC reports are all selected for reasons of their scientific expertise.
The authors’ task is to collate and evaluate the knowledge that is available in international scientific, technical and socio-economic literature using traditional scientific methods and working principles. Then, the reports are sent to specialists for review, and in a second round to government representatives from the member countries of the organizations.
Thus there are over 1200 independent scientific authors and 2500 reviewers who have taken part in the preparation of the IPCC’s Fourth Assessment Report published in 2007.
IPCC's secretariat is based in Geneva and is organized into three working groups and one Task Force.
The first working group evaluates literature in natural science about climate and climate change. The second is concerned with the consequences of climate change, and the potential for adapting to them, while the third working group evaluates the potential for reducing the planet’s emissions of greenhouse gases, and thus limiting the climate changes. Finally, the Task Force is responsible for the National Greenhouse Gas Inventories Program.
IPCC has published four Assessment Reports (in 1990, 1995, 2001 and 2007). Each Assessment Report consists of contributions from the three working groups and a Synthesis Report.
The Fourth Assessment Report has contributed to both the public and politicians gaining increased awareness that climate changes are man-made and are happening faster than earlier assumed. The report shows that climate changes are a reality today, and that the main culprit is greenhouse gas emissions caused by man, and notably CO2 emissions
Himalayan nations to hold first climate talks
South Asian ministers will gather in Nepal next week for talks on the threat that climate change poses to the Himalayas and to the 1.3 billion people dependent on water flowing from the mountains.
Experts say the Himalayan glaciers are melting at an alarming rate and with months to go before a key summit in Copenhagen, mountain nations are hoping to highlight the myriad of problems facing the region.
Climate change campaigners refer to the Himalayas as the "third pole" and say the melting glaciers are the biggest potential contributors to rising sea levels after the north and south poles.
But until now Himalayan governments have not come together to lobby for ambitious emission reduction targets at December's Copenhagen summit, which aims to seal a new international climate change accord.
"Nepal's message needs to be heard, and the message of the mountains needs to be heard," said World Bank water and climate expert Claudia Sadoff, who is helping Nepal's government organise the August 31-September 1 conference.
"The Himalayas have their own very real set of challenges, but there are also a lot of adaptation and mitigation opportunities in the mountains."
Glaciers in the Himalayas, a 2,400-kilometre (1,500-mile) range that sweeps through Pakistan, India, China, Nepal and Bhutan, provide headwaters for Asia's nine largest rivers, a lifeline for the 1.3 billion people who live downstream.
But temperatures in the region have increased by between 0.15 and 0.6 degrees Celsius (0.27 and 1.08 degrees Fahrenheit) per decade for the last 30 years, and the effects are already being felt.
In Nepal and Bhutan, the melting glaciers have formed vast lakes that threaten to burst, devastating communities downstream.
Low-lying Bangladesh has always been prone to flooding, but leading environment scientist Atiq Rahman said the speed at which the Himalayan glaciers were melting meant floods were now "more frequent and more vigorous".
Last year Nepal suffered its driest winter in 40 years, bringing the first widespread forest fires the country has experienced and destroying crops that depend on the winter rains.
Campaigners say that while the effects of climate change on low-lying South Asian countries such as Bangladesh and the Maldives are now well known, there is little international awareness of the vulnerability of the Himalayan region.
"The general impression is that the Himalayas are huge, impregnable, pristine spaces no one can hurt. But the fact is that they are melting," said Tariq Aziz, leader of the WWF's Living Himalayas initiative.
"The Himalayas are not just mountains. They are a source of sustenance for millions and their most valuable commodity is water."
Nepal's government, which has invited environment ministers from across South Asia to attend the talks, said it hoped to "take a regional voice on climate change to Copenhagen".
"The glaciers are melting and the temperatures are rising in the Himalayas," said environment secretary Uday Raj Sharma.
"This will ultimately affect people's livelihoods not only in Nepal but also downstream."
Some observers have expressed concern that India, which opposes binding carbon emission cuts, will drown out the voices of smaller countries such as Nepal, Bhutan and Bangladesh at the Copenhagen talks.
New Delhi does not plan to send anyone from the national government to next week's conference in Nepal, an absence that will inevitably weaken any message that comes out of the talks.
India's environment secretary Jairam Ramesh recently expressed scepticism as to whether the melting of the Himalayan glaciers is caused by climate change, saying more research was needed.
But campaigners say the world cannot afford to wait for concrete evidence before acting to mitigate the effects of the melting glaciers.
They say poor mountain states such as Nepal and Bhutan need urgent international assistance to adapt to the changes and to build early warning systems necessary to prevent devastation from flooding or drought.
"There is still debate on the magnitude of the effects of climate change but the consensus is that already, man-made emissions have created temperature increases," said Simon Lucas, climate change adviser to Britain's Department for International Development in Nepal.
"We already know it is the poorest people who will be worst affected, and the number of people impacted in South Asia will be simply enormous."
Experts say the Himalayan glaciers are melting at an alarming rate and with months to go before a key summit in Copenhagen, mountain nations are hoping to highlight the myriad of problems facing the region.
Climate change campaigners refer to the Himalayas as the "third pole" and say the melting glaciers are the biggest potential contributors to rising sea levels after the north and south poles.
But until now Himalayan governments have not come together to lobby for ambitious emission reduction targets at December's Copenhagen summit, which aims to seal a new international climate change accord.
"Nepal's message needs to be heard, and the message of the mountains needs to be heard," said World Bank water and climate expert Claudia Sadoff, who is helping Nepal's government organise the August 31-September 1 conference.
"The Himalayas have their own very real set of challenges, but there are also a lot of adaptation and mitigation opportunities in the mountains."
Glaciers in the Himalayas, a 2,400-kilometre (1,500-mile) range that sweeps through Pakistan, India, China, Nepal and Bhutan, provide headwaters for Asia's nine largest rivers, a lifeline for the 1.3 billion people who live downstream.
But temperatures in the region have increased by between 0.15 and 0.6 degrees Celsius (0.27 and 1.08 degrees Fahrenheit) per decade for the last 30 years, and the effects are already being felt.
In Nepal and Bhutan, the melting glaciers have formed vast lakes that threaten to burst, devastating communities downstream.
Low-lying Bangladesh has always been prone to flooding, but leading environment scientist Atiq Rahman said the speed at which the Himalayan glaciers were melting meant floods were now "more frequent and more vigorous".
Last year Nepal suffered its driest winter in 40 years, bringing the first widespread forest fires the country has experienced and destroying crops that depend on the winter rains.
Campaigners say that while the effects of climate change on low-lying South Asian countries such as Bangladesh and the Maldives are now well known, there is little international awareness of the vulnerability of the Himalayan region.
"The general impression is that the Himalayas are huge, impregnable, pristine spaces no one can hurt. But the fact is that they are melting," said Tariq Aziz, leader of the WWF's Living Himalayas initiative.
"The Himalayas are not just mountains. They are a source of sustenance for millions and their most valuable commodity is water."
Nepal's government, which has invited environment ministers from across South Asia to attend the talks, said it hoped to "take a regional voice on climate change to Copenhagen".
"The glaciers are melting and the temperatures are rising in the Himalayas," said environment secretary Uday Raj Sharma.
"This will ultimately affect people's livelihoods not only in Nepal but also downstream."
Some observers have expressed concern that India, which opposes binding carbon emission cuts, will drown out the voices of smaller countries such as Nepal, Bhutan and Bangladesh at the Copenhagen talks.
New Delhi does not plan to send anyone from the national government to next week's conference in Nepal, an absence that will inevitably weaken any message that comes out of the talks.
India's environment secretary Jairam Ramesh recently expressed scepticism as to whether the melting of the Himalayan glaciers is caused by climate change, saying more research was needed.
But campaigners say the world cannot afford to wait for concrete evidence before acting to mitigate the effects of the melting glaciers.
They say poor mountain states such as Nepal and Bhutan need urgent international assistance to adapt to the changes and to build early warning systems necessary to prevent devastation from flooding or drought.
"There is still debate on the magnitude of the effects of climate change but the consensus is that already, man-made emissions have created temperature increases," said Simon Lucas, climate change adviser to Britain's Department for International Development in Nepal.
"We already know it is the poorest people who will be worst affected, and the number of people impacted in South Asia will be simply enormous."
Millions in Nepal facing hunger as climate changes
Changing weather patterns have dramatically affected crop production in Nepal, leaving farmers unable to properly feed themselves and pushing them into debt, Oxfam International said in a report released in Katmandu. The British aid agency described the situation as "deeply worrying." "Communities told us crop production is roughly half that of previous years ... Last year many could only grow enough (food) for one month's consumption," said Oxfam's Wayne Gum, adding that less precipitation has been forecast this winter, which will make the situation worse. More extreme temperatures, drier winters and delays in summer monsoons have all compounded the situation, the report said. More than 3.4 million people in Nepal are estimated to require food assistance, and food stocks in farming communities will last only a few months, it warned. Oxfam said Nepal will likely suffer more frequent droughts because of climate change. River levels will decline due to the reduced rainfall and glacial retreat, making it harder to irrigate crops and provide water for livestock.
Subscribe to:
Posts (Atom)