Friday 27 April 2007
GLOBAL WARMING - serious or sensationalist?
So what is the truth about global warming?
Well apparently global warming is the increase in the average temperature of the Earth's near-surface air and oceans in recent decades and its projected continuation.
The average global air temperature near the Earth's surface rose 0.74 ± 0.18 °C (1.3 ± 0.32 °F) during the past century.
The Intergovernmental Panel on Climate Change (IPCC) said, "most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations," which leads to warming of the surface and lower atmosphere by increasing the greenhouse effect. Other phenomena such as solar variation and volcanoes have probably had a relatively small effect. These 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. The American Association of Petroleum Geologists is the only scientific society that rejects these conclusions, and a few individual scientists also disagree with parts of them.
Ok so there is some debate around the cause of global warming.
Climate models referenced by the IPCC have predicted that average global surface temperatures are likely to increase by 1.1 to 6.4 °C (2.0 to 11.5 °F) between 1990 and 2100. The uncertainty in the values reflects the use of differing scenarios of future greenhouse gas emissions as well as uncertainties regarding climate sensitivity. In other words this sounds like a bit of a guess to me. Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a millennium even if no further greenhouse gases are released after this date. This reflects the long average atmospheric lifetime of carbon dioxide (CO2). So are we going to be up to our necks in hot water within a thousand years!?
An increase in global temperatures can in turn cause other changes, including sea level rise and changes in the amount and pattern of rain. There may also be increases in the frequency and intensity of extreme weather events, though it is difficult to connect specific events to global warming (unless you are reporting for a newspaper or similar medium!). Other consequences may include changes in agricultural yields, glacier retreat, reduced summer streamflows, species extinctions and increases in the ranges of disease vectors (although I think we've nearly cracked this with the global community anyway!).
Remaining scientific uncertainties include the exact degree of climate change expected in the future, in particular how changes will vary from region to region around the globe. Now hold on a minute..... is this saying that they don't know what will happen and where? This doesn't fill me with confidence that the original predictions of warming are right or even that they can be certain that we are making a significant contribution to what seems to be, in the grand scheme of things (ie the history of the planet), inevitable change.
There is ongoing political and public debate regarding what, if any, action should be taken to reduce or reverse future warming or to adapt to its expected consequences. Most national governments have signed and ratified the Kyoto Protocol aimed at combating greenhouse gas emissions. I think the Kyoto Protocol is a step in the right direction at controlling emissions but I am not sure it is the answer, if indeed CO2 is a problem.
Carbon dioxide during the last 400,000 years and the rapid rise since the Industrial Revolution and changes in the Earth's orbit around the Sun (Milankovitch cycles) are believed to be the pacemaker of the 100,000 year ice age cycle.
The climate system varies through natural, internal processes and in response to variations in external forcing factors including solar activity, volcanic emissions, variations in the earth's orbit (orbital forcing) and greenhouse gases. The detailed causes of the recent warming remain an active field of research, but the scientific consensus identifies increased levels of greenhouse gases due to human activity as the main influence. This attribution is clearest for the most recent 50 years, for which the most detailed data are available. Contrasting with this view, other hypotheses have been proposed to explain some of the observed increase in global temperatures, including: the warming is within the range of natural variation; the warming is a consequence of coming out of a prior cool period, namely the Little Ice Age; or the warming is primarily a result of variances in solar radiation. Ok so we are back to the same debate as above - is human activity making a difference or not. Could we just be coincidental drop in the ocean of inevitable change?
None of the effects of the above are instantaneous. This is due to the thermal inertia of the Earth's oceans and slow responses of other indirect effects, 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 present day levels, a further warming of about 0.5 °C (0.9 °F) would still occur. Let's remind ourselves that 0.74 ± 0.18 °C was stated as the predicted rise by 2100 as a result of the CO2 emissions.
The greenhouse effect was discovered by Joseph Fourier in 1824 and was first investigated quantitatively by in 1896. It is the process by which absorption and emission of infrared radiation by atmospheric gases warms a planet's atmosphere and surface.
Greenhouse gases create a natural greenhouse effect, without which mean temperatures on Earth would be an estimated 33 °C (59 °F) lower, so that Earth would be uninhabitable. Thus scientists do not "believe in" or "oppose" the greenhouse effect as such; rather, the debate concerns the net effect of the addition of greenhouse gases, while allowing for associated positive and negative feedback mechanisms.
On Earth, the major natural greenhouse gases are water vapor, which causes about 36–70% of the greenhouse effect (not including clouds); CO2, which causes 9–26%; methane, which causes 4–9% (remember the stories on how the cattle in the burger industry where farting their way in to global warming?); and ozone, which causes 3–7%. The atmospheric concentrations of CO2 and methane have increased by 31% and 149% respectively above pre-industrial levels since 1750. This is 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. "About three-quarters of the anthropogenic [man-made] emissions of CO2 to the atmosphere during the past 20 years are due to fossil fuel burning. The rest of the anthropogenic emissions are predominantly due to land-use change, especially deforestation."
The present atmospheric concentration of CO2 is about 383 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, 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.
Positive feedback effects such as the expected release of methane from the melting of permafrost peat bogs in Siberia (possibly up to 70,000 million tonnes) may lead to significant additional sources of greenhouse gas emissions not included in IPCC's climate models.
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. CO2 injected into the atmosphere causes a warming of the atmosphere and the earth's surface. The warming causes more water to be evaporated into the atmosphere. Since water vapor itself acts as a greenhouse gas, this causes still more warming; the warming causes more water vapor to be evaporated, and so forth until a new dynamic equilibrium concentration of water vapor is reached at a slightly higher humidity and with a much larger greenhouse effect than that due to CO2 alone. This feedback effect is reversed only as the CO2 is slowly removed from the atmosphere.
Another important feedback process is ice-albedo feedback. The increased CO2 in the atmosphere warms the Earth's surface and leads to melting of ice near the poles. 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.
Feedback effects due to clouds are an area of ongoing research and debate. Seen from below, clouds absorb infrared radiation and so exert a warming effect. Seen from above, the same clouds reflect sunlight and so exert a cooling effect. Increased global water vapor concentration may or may not cause an increase in global average cloud cover. The net effect of clouds thus has not been well modeled. Positive feedback due to release of CO2 and methane from thawing permafrost is an additional mechanism contributing to warming. Possible positive feedback due to methane release from melting seabed ices is a further mechanism to be considered.
Variations in solar output, possibly amplified by cloud feedbacks, have been suggested as a possible cause of recent warming. A difference between this mechanism and greenhouse warming is that an increase in solar activity should produce a warming of the stratosphere while greenhouse warming should produce a cooling of the stratosphere. Stratospheric warming has not been observed.
Solar variation has probably had a relatively small effect on recent global warming, compared with anthropogenic effects. However, some research has suggested that the Sun's contribution may have been underestimated. Researchers have estimated that the Sun may have minimally contributed about 10–30% of the global surface temperature warming over the period 1980–2002.
From the present to the dawn of human settlement Global temperatures on both land and sea have increased by 0.75 °C (1.4 °F) relative to the period 1860–1900, according to the instrumental temperature record. Since 1979, land temperatures have increased about twice as fast as ocean temperatures (0.25 °C/decade against 0.13 °C/decade). Temperatures in the lower troposphere have increased between 0.12 and 0.22 °C (0.22 and 0.4 °F) per decade since 1979, according to satellite temperature measurements. Temperature is believed to have been relatively stable over the one or two thousand years before 1850, with possibly regional fluctuations such as the Medieval Warm Period or the Little Ice Age.
Based on estimates by NASA's Goddard Institute for Space Studies, 2005 was the warmest year since reliable, widespread instrumental measurements became available in the late 1800s, exceeding the previous record set in 1998 by a few hundredths of a degree. Coincidentally this is around the time when we started to increase CO2 emissions - so again we can't be sure. Anthropogenic emissions of other pollutants—notably sulfate aerosols—can exert a cooling effect by increasing the reflection of incoming sunlight. This partially accounts for the cooling seen in the temperature record in the middle of the twentieth century, though the cooling may also be due in part to natural variability.
Earth has experienced warming and cooling many times in the past. The recent Antarctic EPICA ice core spans 800,000 years, including eight glacial cycles timed by orbital variations with interglacial warm periods comparable to present temperatures.
A rapid buildup of greenhouse gases caused warming in the early Jurassic period (about 180 million years ago), with average temperatures rising by 5 °C (9.0 °F). Woah!!! Surely the dinosaurs weren't driving to work? Research by the Open University indicates that the warming caused the rate of rock weathering to increase by 400%. As such weathering locks away carbon in calcite and dolomite, CO2 levels dropped back to normal over roughly the next 150,000 years. So the Earth sorted itself out then.
I don't know about you but my head hurts after that. So are we contributing (significantly) to global warming? Doesn't it seem as though it might be inevitable anyway?
I think it is good to keep ourselves in check and live in harmony with our mother Earth but can we make a difference, if indeed making a difference will make any difference to the outcome whatever that may or may not be.
Any efforts we make are likely to be lost whether we make those efforts as individuals, communities or countries because there will always be someone who does not believe there is a problem or is benefiting too much financially from their less than green approach to life. Is this a cynical way to look at it? Is this a valid reason not to try and make a difference?
Well apparently global warming is the increase in the average temperature of the Earth's near-surface air and oceans in recent decades and its projected continuation.
The average global air temperature near the Earth's surface rose 0.74 ± 0.18 °C (1.3 ± 0.32 °F) during the past century.
The Intergovernmental Panel on Climate Change (IPCC) said, "most of the observed increase in globally averaged temperatures since the mid-20th century is very likely due to the observed increase in anthropogenic greenhouse gas concentrations," which leads to warming of the surface and lower atmosphere by increasing the greenhouse effect. Other phenomena such as solar variation and volcanoes have probably had a relatively small effect. These 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. The American Association of Petroleum Geologists is the only scientific society that rejects these conclusions, and a few individual scientists also disagree with parts of them.
Ok so there is some debate around the cause of global warming.
Climate models referenced by the IPCC have predicted that average global surface temperatures are likely to increase by 1.1 to 6.4 °C (2.0 to 11.5 °F) between 1990 and 2100. The uncertainty in the values reflects the use of differing scenarios of future greenhouse gas emissions as well as uncertainties regarding climate sensitivity. In other words this sounds like a bit of a guess to me. Although most studies focus on the period up to 2100, warming and sea level rise are expected to continue for more than a millennium even if no further greenhouse gases are released after this date. This reflects the long average atmospheric lifetime of carbon dioxide (CO2). So are we going to be up to our necks in hot water within a thousand years!?
An increase in global temperatures can in turn cause other changes, including sea level rise and changes in the amount and pattern of rain. There may also be increases in the frequency and intensity of extreme weather events, though it is difficult to connect specific events to global warming (unless you are reporting for a newspaper or similar medium!). Other consequences may include changes in agricultural yields, glacier retreat, reduced summer streamflows, species extinctions and increases in the ranges of disease vectors (although I think we've nearly cracked this with the global community anyway!).
Remaining scientific uncertainties include the exact degree of climate change expected in the future, in particular how changes will vary from region to region around the globe. Now hold on a minute..... is this saying that they don't know what will happen and where? This doesn't fill me with confidence that the original predictions of warming are right or even that they can be certain that we are making a significant contribution to what seems to be, in the grand scheme of things (ie the history of the planet), inevitable change.
There is ongoing political and public debate regarding what, if any, action should be taken to reduce or reverse future warming or to adapt to its expected consequences. Most national governments have signed and ratified the Kyoto Protocol aimed at combating greenhouse gas emissions. I think the Kyoto Protocol is a step in the right direction at controlling emissions but I am not sure it is the answer, if indeed CO2 is a problem.
Carbon dioxide during the last 400,000 years and the rapid rise since the Industrial Revolution and changes in the Earth's orbit around the Sun (Milankovitch cycles) are believed to be the pacemaker of the 100,000 year ice age cycle.
The climate system varies through natural, internal processes and in response to variations in external forcing factors including solar activity, volcanic emissions, variations in the earth's orbit (orbital forcing) and greenhouse gases. The detailed causes of the recent warming remain an active field of research, but the scientific consensus identifies increased levels of greenhouse gases due to human activity as the main influence. This attribution is clearest for the most recent 50 years, for which the most detailed data are available. Contrasting with this view, other hypotheses have been proposed to explain some of the observed increase in global temperatures, including: the warming is within the range of natural variation; the warming is a consequence of coming out of a prior cool period, namely the Little Ice Age; or the warming is primarily a result of variances in solar radiation. Ok so we are back to the same debate as above - is human activity making a difference or not. Could we just be coincidental drop in the ocean of inevitable change?
None of the effects of the above are instantaneous. This is due to the thermal inertia of the Earth's oceans and slow responses of other indirect effects, 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 present day levels, a further warming of about 0.5 °C (0.9 °F) would still occur. Let's remind ourselves that 0.74 ± 0.18 °C was stated as the predicted rise by 2100 as a result of the CO2 emissions.
The greenhouse effect was discovered by Joseph Fourier in 1824 and was first investigated quantitatively by in 1896. It is the process by which absorption and emission of infrared radiation by atmospheric gases warms a planet's atmosphere and surface.
Greenhouse gases create a natural greenhouse effect, without which mean temperatures on Earth would be an estimated 33 °C (59 °F) lower, so that Earth would be uninhabitable. Thus scientists do not "believe in" or "oppose" the greenhouse effect as such; rather, the debate concerns the net effect of the addition of greenhouse gases, while allowing for associated positive and negative feedback mechanisms.
On Earth, the major natural greenhouse gases are water vapor, which causes about 36–70% of the greenhouse effect (not including clouds); CO2, which causes 9–26%; methane, which causes 4–9% (remember the stories on how the cattle in the burger industry where farting their way in to global warming?); and ozone, which causes 3–7%. The atmospheric concentrations of CO2 and methane have increased by 31% and 149% respectively above pre-industrial levels since 1750. This is 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. "About three-quarters of the anthropogenic [man-made] emissions of CO2 to the atmosphere during the past 20 years are due to fossil fuel burning. The rest of the anthropogenic emissions are predominantly due to land-use change, especially deforestation."
The present atmospheric concentration of CO2 is about 383 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, 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.
Positive feedback effects such as the expected release of methane from the melting of permafrost peat bogs in Siberia (possibly up to 70,000 million tonnes) may lead to significant additional sources of greenhouse gas emissions not included in IPCC's climate models.
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. CO2 injected into the atmosphere causes a warming of the atmosphere and the earth's surface. The warming causes more water to be evaporated into the atmosphere. Since water vapor itself acts as a greenhouse gas, this causes still more warming; the warming causes more water vapor to be evaporated, and so forth until a new dynamic equilibrium concentration of water vapor is reached at a slightly higher humidity and with a much larger greenhouse effect than that due to CO2 alone. This feedback effect is reversed only as the CO2 is slowly removed from the atmosphere.
Another important feedback process is ice-albedo feedback. The increased CO2 in the atmosphere warms the Earth's surface and leads to melting of ice near the poles. 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.
Feedback effects due to clouds are an area of ongoing research and debate. Seen from below, clouds absorb infrared radiation and so exert a warming effect. Seen from above, the same clouds reflect sunlight and so exert a cooling effect. Increased global water vapor concentration may or may not cause an increase in global average cloud cover. The net effect of clouds thus has not been well modeled. Positive feedback due to release of CO2 and methane from thawing permafrost is an additional mechanism contributing to warming. Possible positive feedback due to methane release from melting seabed ices is a further mechanism to be considered.
Variations in solar output, possibly amplified by cloud feedbacks, have been suggested as a possible cause of recent warming. A difference between this mechanism and greenhouse warming is that an increase in solar activity should produce a warming of the stratosphere while greenhouse warming should produce a cooling of the stratosphere. Stratospheric warming has not been observed.
Solar variation has probably had a relatively small effect on recent global warming, compared with anthropogenic effects. However, some research has suggested that the Sun's contribution may have been underestimated. Researchers have estimated that the Sun may have minimally contributed about 10–30% of the global surface temperature warming over the period 1980–2002.
From the present to the dawn of human settlement Global temperatures on both land and sea have increased by 0.75 °C (1.4 °F) relative to the period 1860–1900, according to the instrumental temperature record. Since 1979, land temperatures have increased about twice as fast as ocean temperatures (0.25 °C/decade against 0.13 °C/decade). Temperatures in the lower troposphere have increased between 0.12 and 0.22 °C (0.22 and 0.4 °F) per decade since 1979, according to satellite temperature measurements. Temperature is believed to have been relatively stable over the one or two thousand years before 1850, with possibly regional fluctuations such as the Medieval Warm Period or the Little Ice Age.
Based on estimates by NASA's Goddard Institute for Space Studies, 2005 was the warmest year since reliable, widespread instrumental measurements became available in the late 1800s, exceeding the previous record set in 1998 by a few hundredths of a degree. Coincidentally this is around the time when we started to increase CO2 emissions - so again we can't be sure. Anthropogenic emissions of other pollutants—notably sulfate aerosols—can exert a cooling effect by increasing the reflection of incoming sunlight. This partially accounts for the cooling seen in the temperature record in the middle of the twentieth century, though the cooling may also be due in part to natural variability.
Earth has experienced warming and cooling many times in the past. The recent Antarctic EPICA ice core spans 800,000 years, including eight glacial cycles timed by orbital variations with interglacial warm periods comparable to present temperatures.
A rapid buildup of greenhouse gases caused warming in the early Jurassic period (about 180 million years ago), with average temperatures rising by 5 °C (9.0 °F). Woah!!! Surely the dinosaurs weren't driving to work? Research by the Open University indicates that the warming caused the rate of rock weathering to increase by 400%. As such weathering locks away carbon in calcite and dolomite, CO2 levels dropped back to normal over roughly the next 150,000 years. So the Earth sorted itself out then.
I don't know about you but my head hurts after that. So are we contributing (significantly) to global warming? Doesn't it seem as though it might be inevitable anyway?
I think it is good to keep ourselves in check and live in harmony with our mother Earth but can we make a difference, if indeed making a difference will make any difference to the outcome whatever that may or may not be.
Any efforts we make are likely to be lost whether we make those efforts as individuals, communities or countries because there will always be someone who does not believe there is a problem or is benefiting too much financially from their less than green approach to life. Is this a cynical way to look at it? Is this a valid reason not to try and make a difference?
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