Climate change is a reality. Today, our world is hotter than it has been in two thousand years. By the end of the century, if current trends continue, the global temperature will likely climb higher than at any time in the past two million years. While the end of the 20th century may not necessarily be the warmest time in Earth's history, what is unique is that the warmth is global and cannot be explained by the natural mechanisms that explain previous warm periods. There is a broad scientific consensus that humanity is in large part responsible for this change, and that choices we make today will decide the climate of the future.
How we are changing the climate?
For more than a century, people have relied on fossil fuels such as oil, coal and gas for their energy needs. Burning these fossil fuels releases the global warming gas carbon dioxide into the atmosphere. Other, even more potent, greenhouse gasses are also playing a role, as is massive deforestation.
"The scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action."-- Joint statement by 11 national science academies to world leaders (full text)
What we know?
While there are still uncertainties, particularly related to the timing, extent and regional variations of climate change, there is mainstream scientific agreement on the key facts:
Certain gasses, such as carbon dioxide, in the atmosphere create a "greenhouse effect", trapping heat and keeping the Earth warm enough to sustain life as we know it.
Burning fossil fuels (coal, oil, etc.) releases more carbon dioxide into the atmosphere. Although not the most potent greenhouse gas, carbon dioxide is the most significant in terms of human effects because of the large quantities emitted.
Carbon dioxide concentrations in the atmosphere are now the highest in 150,000 years.
The 1990's was most likely the warmest decade in history, and 1998 the warmest year.
There is also widespread agreement that:
A certain amount of additional warming - about 1.3º Celsius (2.3º Fahrenheit) compared to pre-industrial levels - is probably inevitable because of emissions so far. Limiting warming to under 2° Celsius (3.6°F) is considered vital to preventing the worst effects of climate change.
If our greenhouse gas emissions are not brought under control, the speed of climate change over the next hundred years will be faster than anything known since before the dawn of civilization.
There is a very real possibility that climate feedback mechanisms will result in a sudden and irreversible climate shift. No one knows how much global warming it would take to trigger such a "doomsday scenario".
There is, in fact, a broad and overwhelming scientific consensus that climate change is occurring, is caused in large part by human activities (such as burning fossil fuels), and if left un-checked will likely have disastrous consequences.
Furthermore, there is solid scientific evidence that we should act now on climate change - and this is reflected in the statements by these definitive scientific authorities.
Joint statement from 11 national academies of science
Issued 7 June 2005, by the national science academies of the United States, United Kingdom, France, Russia, Germany, Japan, Italy, Canada, Brazil, China and India, the statement begins with:
Climate change is real
There will always be uncertainty in understanding a system as complex as the world’s climate. However there is now strong evidence that significant global warming is occurring. The evidence comes from direct measurements of rising surface air temperatures and subsurface ocean temperatures and from phenomena such as increases in average global sea levels, retreating glaciers, and changes to many physical and biological systems. It is likely that most of the warming in recent decades can be attributed to human activities (IPCC 2001). This warming has already led to changes in the Earth's climate.
The statement goes on to conclude:
We urge all nations, in the line with the UNFCCC principles, to take prompt action to reduce the causes ofclimate change, adapt to its impacts and ensure that the issue is included in all relevant national and international strategies.
Intergovernmental Panel on Climate Change
The Intergovernmental Panel on Climate Change (IPCC) was set up by the United Nations in 1988 to assess the scientific, technical and socio-economic information relevant for the understanding of the risk of human induced climate change. About 1,000 experts from around the world are involved in drafting, revising and finalizing IPCC reports. About 2,500 experts take part in the report review process. Thus, the IPCC represents a global consensus of the world's climate change experts. From the IPCC's most recent scientific assessment:
“[M]ost of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations".
"There is new and stronger evidence that most of the observed warming over the last 50 years is attributable to human activities".
"About three quarters of the anthropogenic [human caused] emissions of CO2 to the atmosphere during the past 20 years are due to fossil fuel burning”.
The assessment goes on to warn that there is a risk of feedback loops, which could cause runaway climate change, and that the global warming to date is already having an effect on the biosphere.
Learn more: http://nationalacademies.org/onpi/06072005.pdf
How we are changing the climate?
For more than a century, people have relied on fossil fuels such as oil, coal and gas for their energy needs. Burning these fossil fuels releases the global warming gas carbon dioxide into the atmosphere. Other, even more potent, greenhouse gasses are also playing a role, as is massive deforestation.
"The scientific understanding of climate change is now sufficiently clear to justify nations taking prompt action."-- Joint statement by 11 national science academies to world leaders (full text)
What we know?
While there are still uncertainties, particularly related to the timing, extent and regional variations of climate change, there is mainstream scientific agreement on the key facts:
Certain gasses, such as carbon dioxide, in the atmosphere create a "greenhouse effect", trapping heat and keeping the Earth warm enough to sustain life as we know it.
Burning fossil fuels (coal, oil, etc.) releases more carbon dioxide into the atmosphere. Although not the most potent greenhouse gas, carbon dioxide is the most significant in terms of human effects because of the large quantities emitted.
Carbon dioxide concentrations in the atmosphere are now the highest in 150,000 years.
The 1990's was most likely the warmest decade in history, and 1998 the warmest year.
There is also widespread agreement that:
A certain amount of additional warming - about 1.3º Celsius (2.3º Fahrenheit) compared to pre-industrial levels - is probably inevitable because of emissions so far. Limiting warming to under 2° Celsius (3.6°F) is considered vital to preventing the worst effects of climate change.
If our greenhouse gas emissions are not brought under control, the speed of climate change over the next hundred years will be faster than anything known since before the dawn of civilization.
There is a very real possibility that climate feedback mechanisms will result in a sudden and irreversible climate shift. No one knows how much global warming it would take to trigger such a "doomsday scenario".
There is, in fact, a broad and overwhelming scientific consensus that climate change is occurring, is caused in large part by human activities (such as burning fossil fuels), and if left un-checked will likely have disastrous consequences.
Furthermore, there is solid scientific evidence that we should act now on climate change - and this is reflected in the statements by these definitive scientific authorities.
Joint statement from 11 national academies of science
Issued 7 June 2005, by the national science academies of the United States, United Kingdom, France, Russia, Germany, Japan, Italy, Canada, Brazil, China and India, the statement begins with:
Climate change is real
There will always be uncertainty in understanding a system as complex as the world’s climate. However there is now strong evidence that significant global warming is occurring. The evidence comes from direct measurements of rising surface air temperatures and subsurface ocean temperatures and from phenomena such as increases in average global sea levels, retreating glaciers, and changes to many physical and biological systems. It is likely that most of the warming in recent decades can be attributed to human activities (IPCC 2001). This warming has already led to changes in the Earth's climate.
The statement goes on to conclude:
We urge all nations, in the line with the UNFCCC principles, to take prompt action to reduce the causes ofclimate change, adapt to its impacts and ensure that the issue is included in all relevant national and international strategies.
Intergovernmental Panel on Climate Change
The Intergovernmental Panel on Climate Change (IPCC) was set up by the United Nations in 1988 to assess the scientific, technical and socio-economic information relevant for the understanding of the risk of human induced climate change. About 1,000 experts from around the world are involved in drafting, revising and finalizing IPCC reports. About 2,500 experts take part in the report review process. Thus, the IPCC represents a global consensus of the world's climate change experts. From the IPCC's most recent scientific assessment:
“[M]ost of the observed warming over the last 50 years is likely to have been due to the increase in greenhouse gas concentrations".
"There is new and stronger evidence that most of the observed warming over the last 50 years is attributable to human activities".
"About three quarters of the anthropogenic [human caused] emissions of CO2 to the atmosphere during the past 20 years are due to fossil fuel burning”.
The assessment goes on to warn that there is a risk of feedback loops, which could cause runaway climate change, and that the global warming to date is already having an effect on the biosphere.
Learn more: http://nationalacademies.org/onpi/06072005.pdf
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