Let's Save Our Earth From Global Warming
Monday, September 29, 2008
Friday, September 26, 2008
Increasing Frekuensi, Increasing Intensity of dangerous storms in recent times.
This chart appears to show randomized weather occurances and randomized storm intensity. On closer examination it shows undeniable patterns of increasing frequency and increasing intensities of storms in recent times. The following thirteen illustrations will segregate information to show that the trends are not random, not benign, and definately increasing towards worse.
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Thursday, September 25, 2008
Wednesday, September 24, 2008
The remaining time we are only 7 years
Commentary by Carlos Pascual and Strobe Talbott.
The world may have only seven years to start reducing the annual buildup in green house gas emissions that otherwise threatens global catastrophe within several decades. That means that between Inauguration Day in January 2009 and 2015, either John McCain or Barack Obama will face the most momentous political challenge of all time.
Reflecting a consensus of hundreds of scientists around the world, the Intergovernmental Panel on Climate Change (IPCC) has affirmed that greenhouse gas emissions are raising the Earth's temperature. The Earth is on a trajectory to warm more than 4.5 degrees Fahrenheit by around mid century. Exceeding that threshold could trigger a series of phenomena: Arable land will turn into desert, higher sea levels will flood coastal areas, and changes in the convection of the oceans will alter currents, such as the Gulf Stream, that determine regional weather patterns.
Manhattan and Florida would be under water, while Nevada would have no water at all. Some Russians quip that they would welcome a more temperate climate, but they would probably be sorry to lose St. Petersburg. Countries such as Bangladesh and Mali do not have the resources to mitigate or even to adapt to the impact of climate change; millions would flee coastal flooding and the desertification of farmlands, creating instant "climate refugees."
Urgent and drastic action by the international community is required, and the United States must take the lead.
Americans produce more than four times as much carbon per capita as the Chinese; 12 time as much as Indians; and more than twice as much as citizens of Germany, France, Britain and Japan. Unless the United States acts first, it will have no credibility in persuading other countries to do their share.
To their credit, McCain and Obama support the creation of a cap-and-trade system that would limit national emissions. Trading among firms would put a price on carbon. That is an essential step toward changing industry behavior, encouraging energy conservation and providing an incentive for new technologies. As the most powerful national economy, the United States can set a example for the world in harnessing wind and solar power; "sequestering" (or capturing) carbon from coal plants; and developing cellulosic ethanol and safe civilian nuclear power as alternatives to fossil fuels.
But the domestic obstacles to these and other measures are daunting. While some industries will prosper, other sectors of the economy, especially those that produce or rely on coal, steel and cement, will contract. Electricity prices will increase in the near and middle terms. Many workers and households will need help with the costs of transition.
Coping with the resulting economic and political hardships would be onerous even if the next president inherited forward-looking climate-change policies. But George W. Bush has pursued and "anti-policy," based on a combination of denial, procrastination and backsliding. His successor will have to make up for lost time while also dealing with a half-trillion-dollar federal deficit, a recession and a national housing crunch, a looming health-care crisis, wars in Iraq and Afghanistan, and diplomatic showdowns with North Korea and Iran.
The winner in November will need all the help he can get - including from his opponent, who will go back to the Senate as a major voice on this and other issues. The next president will also need support from the private sector, nongovernmental organizations academia and - crucially - citizens who recognize the consequences if they do not consent to sacrifices and changes in lifestyle.
Many Americans will accept that logic, and make real changes, only if they believe greenhouse gas emissions will affect them personally. Today's adults, even if they will not be around at mid-century, must think about the fate of their children and grandchildren. Obama can look to his two daughters, and McCain to his four grandchildren. They are among nearly 75 million Americans - and 2.2 billion people worldwide - younger than 18. That generation will be in its 40s or 50s when on of tow things happens: Either the temperature of the planet warms more than 4.5 degrees and vast regions slide toward being uninhabitable, or the wisdom of the next president and his fellow leaders around the world pays off in the ultimate reward - survival.
The world may have only seven years to start reducing the annual buildup in green house gas emissions that otherwise threatens global catastrophe within several decades. That means that between Inauguration Day in January 2009 and 2015, either John McCain or Barack Obama will face the most momentous political challenge of all time.
Reflecting a consensus of hundreds of scientists around the world, the Intergovernmental Panel on Climate Change (IPCC) has affirmed that greenhouse gas emissions are raising the Earth's temperature. The Earth is on a trajectory to warm more than 4.5 degrees Fahrenheit by around mid century. Exceeding that threshold could trigger a series of phenomena: Arable land will turn into desert, higher sea levels will flood coastal areas, and changes in the convection of the oceans will alter currents, such as the Gulf Stream, that determine regional weather patterns.
Manhattan and Florida would be under water, while Nevada would have no water at all. Some Russians quip that they would welcome a more temperate climate, but they would probably be sorry to lose St. Petersburg. Countries such as Bangladesh and Mali do not have the resources to mitigate or even to adapt to the impact of climate change; millions would flee coastal flooding and the desertification of farmlands, creating instant "climate refugees."
Urgent and drastic action by the international community is required, and the United States must take the lead.
Americans produce more than four times as much carbon per capita as the Chinese; 12 time as much as Indians; and more than twice as much as citizens of Germany, France, Britain and Japan. Unless the United States acts first, it will have no credibility in persuading other countries to do their share.
To their credit, McCain and Obama support the creation of a cap-and-trade system that would limit national emissions. Trading among firms would put a price on carbon. That is an essential step toward changing industry behavior, encouraging energy conservation and providing an incentive for new technologies. As the most powerful national economy, the United States can set a example for the world in harnessing wind and solar power; "sequestering" (or capturing) carbon from coal plants; and developing cellulosic ethanol and safe civilian nuclear power as alternatives to fossil fuels.
But the domestic obstacles to these and other measures are daunting. While some industries will prosper, other sectors of the economy, especially those that produce or rely on coal, steel and cement, will contract. Electricity prices will increase in the near and middle terms. Many workers and households will need help with the costs of transition.
Coping with the resulting economic and political hardships would be onerous even if the next president inherited forward-looking climate-change policies. But George W. Bush has pursued and "anti-policy," based on a combination of denial, procrastination and backsliding. His successor will have to make up for lost time while also dealing with a half-trillion-dollar federal deficit, a recession and a national housing crunch, a looming health-care crisis, wars in Iraq and Afghanistan, and diplomatic showdowns with North Korea and Iran.
The winner in November will need all the help he can get - including from his opponent, who will go back to the Senate as a major voice on this and other issues. The next president will also need support from the private sector, nongovernmental organizations academia and - crucially - citizens who recognize the consequences if they do not consent to sacrifices and changes in lifestyle.
Many Americans will accept that logic, and make real changes, only if they believe greenhouse gas emissions will affect them personally. Today's adults, even if they will not be around at mid-century, must think about the fate of their children and grandchildren. Obama can look to his two daughters, and McCain to his four grandchildren. They are among nearly 75 million Americans - and 2.2 billion people worldwide - younger than 18. That generation will be in its 40s or 50s when on of tow things happens: Either the temperature of the planet warms more than 4.5 degrees and vast regions slide toward being uninhabitable, or the wisdom of the next president and his fellow leaders around the world pays off in the ultimate reward - survival.
13 Important Things to Do about Global Warming...from the individual to the national
1. Learn about it -- start with this Web site and see the References.
2. Sell the SUV and choose cleaner, more efficient vehicles. Reduce your driving: one gallon of gas burned creates 20 pounds of CO2. Slow down for much better mileage. (Avoid biofuels like corn ethanol that can steal food from a hungry world.)
3. Use efficient appliances, replace light bulbs with low-voltage compact fluorescents, check your home insulation. Buy renewable energy, like wind and solar, from your power company.
4. Companies -- the one you work for and the ones you buy from -- can save lots of money and reduce global warming by taking similar steps toward energy efficiency.
5. Shop smart: Look for products made from recycled materials, created with renewable energy, and which help you save money and reduce pollution. Let the corporations who make our cars, fuels, goods and power know you want their products to be as ecological as possible.
6. Use your vote and influence as a citizen to elect responsive leaders; help them organize the neighborhood and town for energy efficiency.
7. Invite neighbors and schools to cooperate in climate cooling actions: Make pathways for walking and biking; put solar panels on roofs; plant community gardens; combine trips or use electric buses for daily errands and kid transport.
8. Suburban sprawl makes for lots of global warming pollution; plan for walkable communities, lots of trees, open spaces, and public transportation in and between cities.
9. Build new homes and buildings for efficiency and solar power. Follow LEED and green building principles in new and rehab building codes.
10. Support sustainable farming and forestry, including non-food crops to make into ethanol and other biofuels.
11. At all government levels, develop an efficient energy policy, moving away from fossil fuels, and wasteful practices like air shipment of non-urgent parts and products.
12. Export new energy technology to the rest of the world that uses renewable energy sources and helps people live healthier, more efficient lives.
13. ....and start doing these things today.
2. Sell the SUV and choose cleaner, more efficient vehicles. Reduce your driving: one gallon of gas burned creates 20 pounds of CO2. Slow down for much better mileage. (Avoid biofuels like corn ethanol that can steal food from a hungry world.)
3. Use efficient appliances, replace light bulbs with low-voltage compact fluorescents, check your home insulation. Buy renewable energy, like wind and solar, from your power company.
4. Companies -- the one you work for and the ones you buy from -- can save lots of money and reduce global warming by taking similar steps toward energy efficiency.
5. Shop smart: Look for products made from recycled materials, created with renewable energy, and which help you save money and reduce pollution. Let the corporations who make our cars, fuels, goods and power know you want their products to be as ecological as possible.
6. Use your vote and influence as a citizen to elect responsive leaders; help them organize the neighborhood and town for energy efficiency.
7. Invite neighbors and schools to cooperate in climate cooling actions: Make pathways for walking and biking; put solar panels on roofs; plant community gardens; combine trips or use electric buses for daily errands and kid transport.
8. Suburban sprawl makes for lots of global warming pollution; plan for walkable communities, lots of trees, open spaces, and public transportation in and between cities.
9. Build new homes and buildings for efficiency and solar power. Follow LEED and green building principles in new and rehab building codes.
10. Support sustainable farming and forestry, including non-food crops to make into ethanol and other biofuels.
11. At all government levels, develop an efficient energy policy, moving away from fossil fuels, and wasteful practices like air shipment of non-urgent parts and products.
12. Export new energy technology to the rest of the world that uses renewable energy sources and helps people live healthier, more efficient lives.
13. ....and start doing these things today.
The Most Important Things
The Most Important Things You Can Do about Rapid Climate Change:
1. Understand the Problem
2. Do Something Today to Reduce Greenhouse Gas Emissions
This website will help you learn the connection between human-made Carbon Dioxide and rapid climate changes and negative effects around the world. The hard fact is that despite what many nations, companies, cities and people are starting to do to reduce their global warming emissions, the world is putting more CO2 into the air than ever before. The current amount is 385 parts per million (ppm) -- higher than ever in the past 800,000 years.
At the same time, renowned American climatologist Dr. James Hansen of NASA says we already have too much CO2 and other greenhouse gases in the air: "If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted ... CO2 will need to be reduced from its current 385 ppm to at most 350 ppm."
This is scary and controversial, but Dr. Hansen and others believe we must act fast-- as a world of concerned people and leaders taking every action we can to limit greenhouse emissions. 350.org is a new movement of citizens from around the world which I recommend for its clarity of purpose and worthy goal.
1. Understand the Problem
2. Do Something Today to Reduce Greenhouse Gas Emissions
This website will help you learn the connection between human-made Carbon Dioxide and rapid climate changes and negative effects around the world. The hard fact is that despite what many nations, companies, cities and people are starting to do to reduce their global warming emissions, the world is putting more CO2 into the air than ever before. The current amount is 385 parts per million (ppm) -- higher than ever in the past 800,000 years.
At the same time, renowned American climatologist Dr. James Hansen of NASA says we already have too much CO2 and other greenhouse gases in the air: "If humanity wishes to preserve a planet similar to that on which civilization developed and to which life on Earth is adapted ... CO2 will need to be reduced from its current 385 ppm to at most 350 ppm."
This is scary and controversial, but Dr. Hansen and others believe we must act fast-- as a world of concerned people and leaders taking every action we can to limit greenhouse emissions. 350.org is a new movement of citizens from around the world which I recommend for its clarity of purpose and worthy goal.
10 MYTHS about Global Warming
Don't believe these commonly heard statements:
* It isn't really happening (documented science overwhelmingly shows temperatures rising rapidly)
* It's natural (temperature increases, especially since the 1970's, are far above natural variations)
* Any effects well be very gradual (not only are severe storms getting stronger, but climate history shows sharp climate changes can occur abruptly, in only a few years)
* It does not affect the U.S. (the U.S. is experiencing rising sea levels, more severe storms and droughts, die-off of forests, altered animal migrations, and loss of glaciers such as those in Glacier National Park)
* It will be good for us (some areas may become more pleasantly warm, but the cost of negative effects will far outweigh any benefits; disease and heat deaths are increasing)
* Agriculture will benefit (CO2 may make some crops grow faster, but also will accelerate weeds, pests and droughts; crops may not grow well where they once did as climate zones shift.)
* It's being handled by our government (The current U.S. Administration advocates studying, not dealing with, global warming; its energy policy completely based on burning more coal & oil. Most state and local governments are unprepared for major changes)
* It's not a big deal compared to national security (Global warming is actually the most serious threat to the widest range of human concerns. Our national and world security is directly threatened by negative climate effects on weather, water supply, disease, agriculture, marine resources, and health)
* Technology will solve the problem for us (Massive "fixes" like burying greenhouse gases are very unlikely, but many smaller changes can make a difference AND are available now)
* There's nothing to be done anyway (Everyone can make a difference today)
* It isn't really happening (documented science overwhelmingly shows temperatures rising rapidly)
* It's natural (temperature increases, especially since the 1970's, are far above natural variations)
* Any effects well be very gradual (not only are severe storms getting stronger, but climate history shows sharp climate changes can occur abruptly, in only a few years)
* It does not affect the U.S. (the U.S. is experiencing rising sea levels, more severe storms and droughts, die-off of forests, altered animal migrations, and loss of glaciers such as those in Glacier National Park)
* It will be good for us (some areas may become more pleasantly warm, but the cost of negative effects will far outweigh any benefits; disease and heat deaths are increasing)
* Agriculture will benefit (CO2 may make some crops grow faster, but also will accelerate weeds, pests and droughts; crops may not grow well where they once did as climate zones shift.)
* It's being handled by our government (The current U.S. Administration advocates studying, not dealing with, global warming; its energy policy completely based on burning more coal & oil. Most state and local governments are unprepared for major changes)
* It's not a big deal compared to national security (Global warming is actually the most serious threat to the widest range of human concerns. Our national and world security is directly threatened by negative climate effects on weather, water supply, disease, agriculture, marine resources, and health)
* Technology will solve the problem for us (Massive "fixes" like burying greenhouse gases are very unlikely, but many smaller changes can make a difference AND are available now)
* There's nothing to be done anyway (Everyone can make a difference today)
Tuesday, September 23, 2008
Habitat and Arctic Sea Ice Loss
Polar Bear Listed in Endangered Species Act, but U.S. Government Limits Its Protection.
The polar bear was officially listed as threatened under the U.S. endangered species act (ESA) on May 14, 2008. This the first creature brought under the act's protection for habitat loss that is linked to global warming. The official reason given was loss of Arctic sea ice and predictions that the ice will continue to decrease. Although global warming has been identified by most atmospheric and polar scientists as the main reason for Arctic warming and melting of sea ice, the U.S. Interior Department did not use this as a reason and clearly signaled it would not apply the law to greenhouse gas emissions.
The polar bear was officially listed as threatened under the U.S. endangered species act (ESA) on May 14, 2008. This the first creature brought under the act's protection for habitat loss that is linked to global warming. The official reason given was loss of Arctic sea ice and predictions that the ice will continue to decrease. Although global warming has been identified by most atmospheric and polar scientists as the main reason for Arctic warming and melting of sea ice, the U.S. Interior Department did not use this as a reason and clearly signaled it would not apply the law to greenhouse gas emissions.
Dirk Kempthorne, Interior Secretary, specifically said the listing would not prevent any sea ice from melting and that he would "make certain the ESA isn't abused to make global warming policies." This despite clear language in the ESA to control any activity causing harm to a listed species and requiring government agencies specifically not to jeopardize species by their actions. The wording of the listing document appears to be an attempt of the government to list the bear due to clear evidence of shrinking habitat yet not take all the steps to limit the loss. It seems analogous to President Bush's notorious "signing statements" limiting his acceptance of a Congressional law.
This could set up another court challenge by NGOs like the Center for Biological Diversity which originally brought the proposal and took the Interior Dept to court twice to get action.
"Threatened" under the ESA means a plant or animal may soon become endangered (at immediate risk of going extinct) if actions are not taken to protect it and its habitat.
Effects of global warming
The effects of global warming on the environment and human life are numerous, varied, accelerating and taking scientists studying global warming by suprise.Scenarios studied by the Intergovernmental Panel on Climate Change (IPCC) predict that global warming will continue and get worse much faster than was expected even in their last report. The IPCC reports attribute many specific natural phenomena to human causes. The expected long range effects of recent climate change may already be observed. Raising sea levels, glacier retreat, Arctic shrinkage, and altered patterns of agriculture are cited as direct consequences of human activities. Predictions for secondary and regional effects include extreme weather events, an expansion of tropical diseases, changes in the timing of seasonal patterns in ecosystems, and drastic economic impact. Concerns have led to political activism advocating proposals to mitigate, eliminate, or adapt to it.
Feedbacks
The effects of forcing agents on the climate are complicated by various feedback processes. One of the most pronounced feedback effects relates to the evaporation of water. Warming by the addition of long-lived greenhouse gases such as CO2 will cause more water to evaporate into the atmosphere. Since water vapor is a greenhouse gas, the atmosphere warms further; this warming causes more water vapor to evaporate (a positive feedback), and so on until other processes stop the feedback loop. The result is a much larger greenhouse effect than that due to CO2 alone. Although this feedback process causes an increase in the absolute moisture content of the air, the relative humidity stays nearly constant or even decreases slightly because the air is warmer. This feedback effect can only be reversed slowly as CO2 has a long average atmospheric lifetime.
Feedback effects due to clouds are an area of ongoing research. Seen from below, clouds emit infrared radiation back to the surface, and so exert a warming effect; seen from above, clouds reflect sunlight and emit infrared radiation to space, and so exert a cooling effect. Whether the net effect is warming or cooling depends on details such as the type and altitude of the cloud. These details are difficult to represent in climate models, in part because clouds are much smaller than the spacing between points on the computational grids of climate models.
A subtler feedback process relates to changes in the lapse rate as the atmosphere warms. The atmosphere's temperature decreases with height in the troposphere. Since emission of infrared radiation varies with the fourth power of temperature, longwave radiation emitted from the upper atmosphere is less than that emitted from the lower atmosphere. Most of the radiation emitted from the upper atmosphere escapes to space, while most of the radiation emitted from the lower atmosphere is re-absorbed by the surface or the atmosphere. Thus, the strength of the greenhouse effect depends on the atmosphere's rate of temperature decrease with height: if the rate of temperature decrease is greater the greenhouse effect will be stronger, and if the rate of temperature decrease is smaller then the greenhouse effect will be weaker. Both theory and climate models indicate that warming will reduce the decrease of temperature with height, producing a negative lapse rate feedback that weakens the greenhouse effect. Measurements of the rate of temperature change with height are very sensitive to small errors in observations, making it difficult to establish whether the models agree with observations.
Another important feedback process is ice-albedo feedback. When global temperatures increase, ice near the poles melts at an increasing rate. As the ice melts, land or open water takes its place. Both land and open water are on average less reflective than ice, and thus absorb more solar radiation. This causes more warming, which in turn causes more melting, and this cycle continues.
Positive feedback due to release of CO2 and CH4 from thawing permafrost, such as the frozen peat bogs in Siberia, is an additional mechanism that could contribute to warming. Similarly a massive release of CH4 from methane clathrates in the ocean could cause rapid warming, according to the clathrate gun hypothesis.
The ocean's ability to sequester carbon is expected to decline as it warms. This is because the resulting low nutrient levels of the mesopelagic zone (about 200 to 1000 m depth) limits the growth of diatoms in favor of smaller phytoplankton that are poorer biological pumps of carbon.
Greenhouse gases in the atmosphere
The greenhouse effect was discovered by Joseph Fourier in 1824 and was first investigated quantitatively by Svante Arrhenius in 1896. It is the process by which absorption and emission of infrared radiation by atmospheric gases warm a planet's lower atmosphere and surface.
Existence of the greenhouse effect as such is not disputed. Naturally occurring greenhouse gases have a mean warming effect of about 33 °C (59 °F), without which Earth would be uninhabitable. On Earth, the major greenhouse gases are water vapor, which causes about 36–70 percent of the greenhouse effect (not including clouds); carbon dioxide (CO2), which causes 9–26 percent; methane (CH4), which causes 4–9 percent; and ozone, which causes 3–7 percent. The issue is how the strength of the greenhouse effect changes when human activity increases the atmospheric concentrations of some greenhouse gases.
Human activity since the industrial revolution has increased the concentration of various greenhouse gases, leading to increased radiative forcing from CO2, methane, tropospheric ozone, CFCs and nitrous oxide. Molecule for molecule, methane is a more effective greenhouse gas than carbon dioxide, but its concentration is much smaller so that its total radiative forcing is only about a fourth of that from carbon dioxide. Some other naturally occurring gases contribute small fractions of the greenhouse effect; one of these, nitrous oxide (N2O), is increasing in concentration owing to human activity such as agriculture. The atmospheric concentrations of CO2 and CH4 have increased by 31% and 149% respectively since the beginning of the industrial revolution in the mid-1700s. These levels are considerably higher than at any time during the last 650,000 years, the period for which reliable data has been extracted from ice cores. From less direct geological evidence it is believed that CO2 values this high were last attained 20 million years ago. Fossil fuel burning has produced approximately three-quarters of the increase in CO2 from human activity over the past 20 years. Most of the rest is due to land-use change, in particular deforestation.
The present atmospheric concentration of CO2 is about 385 parts per million (ppm) by volume. Future CO2 levels are expected to rise due to ongoing burning of fossil fuels and land-use change. The rate of rise will depend on uncertain economic, sociological, technological, and natural developments, but may be ultimately limited by the availability of fossil fuels. The IPCC Special Report on Emissions Scenarios gives a wide range of future CO2 scenarios, ranging from 541 to 970 ppm by the year 2100. Fossil fuel reserves are sufficient to reach this level and continue emissions past 2100, if coal, tar sands or methane clathrates are extensively used.
Existence of the greenhouse effect as such is not disputed. Naturally occurring greenhouse gases have a mean warming effect of about 33 °C (59 °F), without which Earth would be uninhabitable. On Earth, the major greenhouse gases are water vapor, which causes about 36–70 percent of the greenhouse effect (not including clouds); carbon dioxide (CO2), which causes 9–26 percent; methane (CH4), which causes 4–9 percent; and ozone, which causes 3–7 percent. The issue is how the strength of the greenhouse effect changes when human activity increases the atmospheric concentrations of some greenhouse gases.
Human activity since the industrial revolution has increased the concentration of various greenhouse gases, leading to increased radiative forcing from CO2, methane, tropospheric ozone, CFCs and nitrous oxide. Molecule for molecule, methane is a more effective greenhouse gas than carbon dioxide, but its concentration is much smaller so that its total radiative forcing is only about a fourth of that from carbon dioxide. Some other naturally occurring gases contribute small fractions of the greenhouse effect; one of these, nitrous oxide (N2O), is increasing in concentration owing to human activity such as agriculture. The atmospheric concentrations of CO2 and CH4 have increased by 31% and 149% respectively since the beginning of the industrial revolution in the mid-1700s. These levels are considerably higher than at any time during the last 650,000 years, the period for which reliable data has been extracted from ice cores. From less direct geological evidence it is believed that CO2 values this high were last attained 20 million years ago. Fossil fuel burning has produced approximately three-quarters of the increase in CO2 from human activity over the past 20 years. Most of the rest is due to land-use change, in particular deforestation.
The present atmospheric concentration of CO2 is about 385 parts per million (ppm) by volume. Future CO2 levels are expected to rise due to ongoing burning of fossil fuels and land-use change. The rate of rise will depend on uncertain economic, sociological, technological, and natural developments, but may be ultimately limited by the availability of fossil fuels. The IPCC Special Report on Emissions Scenarios gives a wide range of future CO2 scenarios, ranging from 541 to 970 ppm by the year 2100. Fossil fuel reserves are sufficient to reach this level and continue emissions past 2100, if coal, tar sands or methane clathrates are extensively used.
Causes
The Earth's climate changes in response to external forcing, including variations in its orbit around the Sun (orbital forcing), changes in solar luminosity, volcanic eruptions, and atmospheric greenhouse gas concentrations. The detailed causes of the recent warming remain an active field of research, but the scientific consensus is that the increase in atmospheric greenhouse gases due to human activity caused most of the warming observed since the start of the industrial era. This attribution is clearest for the most recent 50 years, for which the most detailed data are available. Some other hypotheses departing from the consensus view have been suggested to explain most of the temperature increase. One such hypothesis proposes that warming may be the result of variations in solar activity.
None of the effects of forcing are instantaneous. The thermal inertia of the Earth's oceans and slow responses of other indirect effects mean that the Earth's current climate is not in equilibrium with the forcing imposed. Climate commitment studies indicate that even if greenhouse gases were stabilized at 2000 levels, a further warming of about 0.5 °C (0.9 °F) would still occur.
None of the effects of forcing are instantaneous. The thermal inertia of the Earth's oceans and slow responses of other indirect effects mean that the Earth's current climate is not in equilibrium with the forcing imposed. Climate commitment studies indicate that even if greenhouse gases were stabilized at 2000 levels, a further warming of about 0.5 °C (0.9 °F) would still occur.
Global Warming
Global warming is the increase in the average measured temperature of the Earth's near-surface air and oceans since the mid-20th century, and its projected continuation.
The average global air temperature near the Earth's surface increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 100 years ending in 2005.
The Intergovernmental Panel on Climate Change (IPCC) concludes "most of the observed increase in globally averaged temperatures since the mid-twentieth century is very likely due to the observed increase in anthropogenic (man-made) greenhouse gas concentrations"via an enhanced greenhouse effect. Natural phenomena such as solar variation combined with volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward.
These basic conclusions have been endorsed by at least 30 scientific societies and academies of science, including all of the national academies of science of the major industrialized countries. While individual scientists have voiced disagreement with some findings of the IPCC, the overwhelming majority of scientists working on climate change agree with the IPCC's main conclusions.
Climate model projections summarized by the IPCC indicate that average global surface temperature will likely rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the twenty-first century. This range of values results from the use of differing scenarios of future greenhouse gas emissions as well as models with differing climate sensitivity. Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a thousand years even if greenhouse gas levels are stabilized. The delay in reaching equilibrium is a result of the large heat capacity of the oceans.
Increasing global temperature is expected to cause sea levels to rise, an increase in the intensity of extreme weather events, and significant changes to the amount and pattern of precipitation, likely leading to an expanse of tropical areas and increased pace of desertification. Other expected effects of global warming include changes in agricultural yields, modifications of trade routes, glacier retreat, mass species extinctions and increases in the ranges of disease vectors.
Remaining scientific uncertainties include the amount of warming expected in the future, and how warming and related changes will vary from region to region around the globe. Most national governments have signed and ratified the Kyoto Protocol aimed at reducing greenhouse gas emissions, but there is ongoing political and public debate worldwide regarding what, if any, action should be taken to reduce or reverse future warming or to adapt to its expected consequences.
The average global air temperature near the Earth's surface increased 0.74 ± 0.18 °C (1.33 ± 0.32 °F) during the 100 years ending in 2005.
The Intergovernmental Panel on Climate Change (IPCC) concludes "most of the observed increase in globally averaged temperatures since the mid-twentieth century is very likely due to the observed increase in anthropogenic (man-made) greenhouse gas concentrations"via an enhanced greenhouse effect. Natural phenomena such as solar variation combined with volcanoes probably had a small warming effect from pre-industrial times to 1950 and a small cooling effect from 1950 onward.
These basic conclusions have been endorsed by at least 30 scientific societies and academies of science, including all of the national academies of science of the major industrialized countries. While individual scientists have voiced disagreement with some findings of the IPCC, the overwhelming majority of scientists working on climate change agree with the IPCC's main conclusions.
Climate model projections summarized by the IPCC indicate that average global surface temperature will likely rise a further 1.1 to 6.4 °C (2.0 to 11.5 °F) during the twenty-first century. This range of values results from the use of differing scenarios of future greenhouse gas emissions as well as models with differing climate sensitivity. Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a thousand years even if greenhouse gas levels are stabilized. The delay in reaching equilibrium is a result of the large heat capacity of the oceans.
Increasing global temperature is expected to cause sea levels to rise, an increase in the intensity of extreme weather events, and significant changes to the amount and pattern of precipitation, likely leading to an expanse of tropical areas and increased pace of desertification. Other expected effects of global warming include changes in agricultural yields, modifications of trade routes, glacier retreat, mass species extinctions and increases in the ranges of disease vectors.
Remaining scientific uncertainties include the amount of warming expected in the future, and how warming and related changes will vary from region to region around the globe. Most national governments have signed and ratified the Kyoto Protocol aimed at reducing greenhouse gas emissions, but there is ongoing political and public debate worldwide regarding what, if any, action should be taken to reduce or reverse future warming or to adapt to its expected consequences.
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