Trace gases are gases that make up a tiny percentage of the Earth’s atmosphere. Even though they account for only a small percentage of what’s in our atmosphere, they contribute substantially to warming of the Earth's surface and atmosphere because they trap the infrared (heat) radiation emitted by the Earth. Jump to “The Atmopshere has a Greenhouse Effect because of Trace Gases”
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Culture, Climate Science & Education
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Principle Five: The Greenhouse Effect
The Cultural Value is Balance
Episode Five: Like a Buffalo Robe on a Hot Day
Episode 5: Like a Buffalo Robe
Transcript with Description of Visuals
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Visual |
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Soft instrumental music: |
Looking out across a broad valley from the air, a large lake in the foreground and a tall range of mountains in the background. The sun is just cresting the snow-covered Mission Mountains. |
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I have grown up on this land, like my Sileʔ and his grandpa and his grandpa before that. |
A long row of teepees in a grassy field with hills in the background. |
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My name is Alyssa Pretty On Top, and I want to share with you what I'm learning about the climate. |
Close up of Alyssa’s face. She is a girl of about 12 or 14. |
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The stories are a lot like the stories told by my teachers. |
A single teepee and outside of it, Alyssa, her mother, and her grandfather sit on a bench, a campfire burning in the foreground. Her grandfather is telling a story, gesturing with his hands as he speaks. |
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They talk about the last Ice Age too and they talk about how the climate is changing now, getting warmer. |
Alyssa sitting in a classroom with other students. |
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Shandin Pete: Well, hydrologists we're interested in exact measurements, right? We want to know exactly what the temperate is. So we measure it. You guys been swimming this summer? Anybody? No? You guys don't swim? |
Tribal college instructor Shandin Pete is standing before the class, lecturing. |
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Alyssa: |
Shandin lecturing. |
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So if we look at a graph of Earth's average atmospheric temperature we can see that over time |
Shandin spreads his arms and a transparent graph appears. It looks as though he holds it with his hands. |
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Earth's temperature has slowly risen. |
A line showing temperature appears, climbing across the graph. It shows rising temperatures, and Shandin points at and follows it with his finger as it climbs. |
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Alyssa: |
Alyssa listening. |
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Humans are burning and releasing far too many greenhouse gases into the atmosphere. |
Shandin now holds his hands out as if he is cradling a large ball. Suddenly a transparent globe of the Earth appears, the continents in white. Red clouds of gas suddenly appear and surround the Earth. |
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Imagine being forced to wear a thick buffalo robe on a hot summer day. That's basically what we are doing to our planet. |
Four kids are sprawled out on a blanket on a dry lake bed, tall mountains in the background. Several other kids carry a large buffalo robe and lay it on top of the kids. |
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Shandin: |
The kids, looking out from beneath the robe, begin to grow hot. |
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Alyssa’s grandfather: |
Alyssa’s grandfather standing above the kids, talking to them. |
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The world's in trouble, it's burning up. |
Looking down on the kids as the camera rises higher and higher. |
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Alyssa: |
The camera rises so high the buffalo robe is the size of a postage stamp on an expanse of dry, brown, lake bed. People in chairs are seated near by, watching. |
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Soft instrumental music |
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The following credits in white text over a black background: |
Principle 5
What You Need to Know About Principle 5: The Greenhouse Effect makes Earth suitable for life.
Without the greenhouse effect the Earth’s surface temperature would be around 0° F instead of the 58° F that it is. Clearly, there’s something in the atmosphere keeping the Earth warm for humans and other living things. That “something” in the atmosphere is greenhouse gases. These gases make Earth warm enough for life to exist. Click the tabs below to learn more about greenhouse gases:
click the tabs to open
- What is the Greenhouse Effect?
The term “greenhouse effect” is the process whereby heat radiating from the Earth’s surface is absorbed by greenhouse gases in the atmosphere where it is re-radiated back in all directions. Since part of this re-radiation is back towards the surface of the earth, it results in an increase in the average surface temperature of the Earth. Jump to “What is the Greenhouse Effect?”
- The Atmosphere has a Greenhouse Effect because of Trace Gases
- Water Vapor is the Most Abundant Greenhouse Gas
Water vapor is the most abundant greenhouse gas, but it’s role is complex because as water vapor increases as the Earth's atmosphere warms but so does the possibility of clouds and precipitation, which are some of the most important feedback mechanisms to the greenhouse effect. Jump to “Water Vapor is the Most Abundant Greenhouse Gas”
- The Two Most Important Greenhouse Gases: CO2 and Methane
More often than not, calculations of carbon footprint only calculate carbon dioxide. However, there is another greenhouse gas, methane, that should also be considered because it has a warming potential significantly higher than carbon dioxide. Jump to “The Two Most Important Greenhouse Gases: CO2 and Methane”
- Natural Processes Cannot Explain Recent Rapid Changes in Earth’s Climate
Natural processes driving Earth’s long-term climate variability do not explain the rapid climate change observed in recent decades. Human impacts play a major role in climate change. Future changes in climate may be rapid compared to historical changes. Jump to “Natural Processes Cannot Explain Recent Rapid Changes in Earth’s Climate”
Principle 5a
What is the Greenhouse Effect?
You can think of the atmosphere as acting like a blanket. Think of yourself under a blanket in a cold room. You represent the Earth, a warm body giving off energy, what we usually call “heat”. The blanket represents the atmospheric layer of greenhouse gases. Read More…
What is the Greenhouse Effect?
You can think of the atmosphere as acting like a blanket. Think of yourself under a blanket in a cold room. You represent the Earth, a warm body giving off energy, what we usually call “heat”. The blanket represents the atmospheric layer of greenhouse gases.
As the heat energy leaves your body it is absorbed by the fibers of the blanket. As they give off some of that energy, they warm the next layer of fibers and so on and on until some energy leaves the outermost cold fiber layer and is lost to the room.
This is what is occurring for the Earth as well. The increased amounts of greenhouse gases our activities are adding to the atmosphere—you can think of them like adding a blanket or two to your bed—have upset the balance that was in place since the end of the last ice age. As a result, the Earth is getting warmer than it was before we started burning large amounts of fossil fuels.
The incoming radiation from the sun is mostly in the visible part of the spectrum. It is shortwave radiation called ultraviolet (UV) (the rays that give us sunburn) and visible light.
Being much cooler than the sun, the Earth emits far less energy, most of it at infrared wavelengths (which we can’t see but can feel — another common name for long wave infrared radiation is heat). Infrared radiation is longwave radiation.
Some of the Earth’s outgoing radiation (the heat) escapes through the atmosphere directly to space. Most of it, though, is absorbed en route by clouds and greenhouse gases (including water vapor). The clouds and greenhouse gases in turn radiate heat back to the Earth’s surface and release some out to space. Thus, Earth’s energy budget is maintained in radiation from the sun and a blend of outgoing radiation from a warm surface and a cooler atmosphere.
In short, here are the percentages of what happens to the sunlight that hits the earth:
The air’s two main components — nitrogen and oxygen — are not good at absorbing heat radiation from the Earth, in part because they have a simple, linear, two-atom structure. Some of the other gases in the atmosphere, however, have three or more atoms and are branched molecules.
Their more complex structure allows them to capture energy far out of proportion to their abundance (they are very scarce). These are the greenhouse gases, and inspite of their very low abundance, they act as a blanket, trapping heat and keeping the earth habitable. The problem is, when we increase their abundance, as we are doing by burning fossil fuels, they end up heating the Earth.
What Is the Greenhouse Effect? Left: Naturally occurring greenhouse gases — carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O) — normally trap some of the sun’s heat, keeping the planet from freezing. Right: Human activities, such as the burning of fossil fuels, are increasing greenhouse gas levels, leading to an enhanced greenhouse effect. The result is global warming and unprecedented rates of climate change. Credit: Will Elder, National Park Service
by Marc Lallanila | January 28, 2015 07:40pm ET
Source: http://www.livescience.com/37743-greenhouse-effect.html
While other planets in Earth's solar system are either scorching hot or bitterly cold, Earth's surface has relatively mild, stable temperatures. Earth enjoys these temperatures because of its atmosphere, which is the thin layer of gases that cloak and protect the planet.
However, 97 percent of climate scientists agree that humans have changed Earth's atmosphere in dramatic ways over the past two centuries, resulting in global warming. To understand global warming, it's first necessary to become familiar with the greenhouse effect, though.
Energy in, energy out
There's a delicate balancing act occurring every day all across the Earth, involving the radiation the planet receives from space and the radiation that's reflected back out to space.
Earth is constantly bombarded with enormous amounts of radiation, primarily from the sun. This solar radiation strikes the Earth's atmosphere in the form of visible light, plus ultraviolet (UV), infrared (IR) and other types of radiation that are invisible to the human eye.
UV radiation has a shorter wavelength and a higher energy level than visible light, while IR radiation has a longer wavelength and a weaker energy level. About 30 percent of the radiation striking Earth's atmosphere is immediately reflected back out to space by clouds, ice, snow, sand and other reflective surfaces, according to NASA. The remaining 70 percent of incoming solar radiation is absorbed by the oceans, the land and the atmosphere. As they heat up, the oceans, land and atmosphere release heat in the form of IR thermal radiation, which passes out of the atmosphere and into space.
It's this equilibrium of incoming and outgoing radiation that makes the Earth habitable, with an average temperature of about 59 degrees Fahrenheit (15 degrees Celsius), according to NASA. Without this atmospheric equilibrium, Earth would be as cold and lifeless as its moon, or as blazing hot as Venus. The moon, which has almost no atmosphere, is about minus 243 F (minus 153 C) on its dark side. Venus, on the other hand, has a very dense atmosphere that traps solar radiation; the average temperature on Venus is about 864 F (462 C).
The greenhouse effect
The exchange of incoming and outgoing radiation that warms the Earth is often referred to as the greenhouse effect because a greenhouse works in much the same way.
Incoming UV radiation easily passes through the glass walls of a greenhouse and is absorbed by the plants and hard surfaces inside. Weaker IR radiation, however, has difficulty passing through the glass walls and is trapped inside, thus warming the greenhouse. This effect lets tropical plants thrive inside a greenhouse, even during a cold winter.
A similar phenomenon takes place in a car parked outside on a cold, sunny day. Incoming solar radiation warms the car's interior, but outgoing thermal radiation is trapped inside the car's closed windows.
Greenhouse gases and global warming
"Gas molecules that absorb thermal infrared radiation, and are in significant enough quantity, can force the climate system. These type of gas molecules are called greenhouse gases," Michael Daley, an associate professor of Environmental Science at Lasell College told Live Science. Carbon dioxide (CO2) and other greenhouse gases act like a blanket, absorbing IR radiation and preventing it from escaping into outer space. The net effect is the gradual heating of Earth's atmosphere and surface, a process known as global warming.
These greenhouse gases include water vapor, CO2, methane, nitrous oxide (N2O) and other gases, according to the Environmental Protection Agency (EPA). Since the dawn of the Industrial Revolution in the early 1800s, the burning of fossil fuels like coal, oil and gasoline have greatly increased the concentration of greenhouse gases in the atmosphere, especially CO2, National Oceanic and Atmospheric Administration (NOAA). "Deforestation is the second largest anthropogenic source of carbon dioxide to the atmosphere ranging between 6percent and 17 percent," said Daley.
Atmospheric CO2 levels have increased by more than 40 percent since the beginning of the Industrial Revolution, from about 280 parts per million (ppm) in the 1800s to 400 ppm today. The last time Earth's atmospheric levels of CO2 reached 400 ppm was during the Pliocene Epoch, between 5 million and 3 million years ago, according to the University of California, San Diego's Scripps Institution of Oceanography.
The greenhouse effect, combined with increasing levels of greenhouse gases and the resulting global warming, is expected to have profound implications, according to the near-universal consensus of scientists.
If global warming continues unchecked, it will cause significant climate change, a rise in sea levels, increasing ocean acidification, extreme weather events and other severe natural and societal impacts, according to NASA, the EPA and other scientific and governmental bodies.
Can the greenhouse effect be reversed?
Many scientists agree that the damage to the Earth's atmosphere and climate is past the point of no return or that the damage is near the point of no return. "I agree that we have passed the point of avoiding climate change," Josef Werne, an associate professor at the department of geology & planetary science at the University of Pittsburgh told Live Science. In Werne's opinion, there are three options from this point forward:
Keith Peterman, a professor of chemistry at York College of Pennsylvania, and Gregory Foy, an associate professor of chemistry at York College of Pennsylvania believes that the damage isn't to that point yet, and that international agreements and action can save the planet's atmosphere.
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Principle 5b
The Atmopshere has a Greenhouse Effect because of Trace Gases
The majority of the Earth's atmosphere is composed of a mixture of only a few gases—nitrogen, oxygen, and argon; combined these three gases comprise more than 99.5% of all the gas molecules in the atmosphere.
These gases, by far the most abundant in the atmosphere, exhibit almost no effect on warming the earth and its atmosphere because they do not absorb visible or infrared radiation. However, there are minor gases that comprise only a small portion of the atmosphere that do absorb infrared radiation. These are called “trace” gases. Read More…
The Atmopshere has a Greenhouse Effect because of Trace Gases
The majority of the Earth's atmosphere is composed of a mixture of only a few gases—nitrogen, oxygen, and argon; combined these three gases comprise more than 99.5% of all the gas molecules in the atmosphere.
These gases, by far the most abundant in the atmosphere, exhibit almost no effect on warming the earth and its atmosphere because they do not absorb visible or infrared radiation. However, there are minor gases that comprise only a small portion of the atmosphere that do absorb infrared radiation. These are called “trace” gases.
Trace gases are gases that make up a tiny percentage of the Earth’s atmosphere. But even though they account for only a small percentage of what’s in our atmosphere, they contribute substantially to warming of the Earth's surface and atmosphere because they trap the infrared (heat) radiation emitted by the Earth.
Since these trace gases influence the Earth in a manner somewhat similar to a greenhouse, they are referred to as GreenHouse Gases.
In short, the greenhouse effects works like this: The Sun radiates energy at very short wavelengths, predominately in the visible or near-visible (e.g., ultraviolet) part of the spectrum. Roughly one-third of the solar energy that reaches the top of Earth’s atmosphere is reflected directly back to space. The remaining two-thirds is absorbed by the surface and, to a lesser extent, by the atmosphere.
To balance the absorbed incoming energy, the Earth must, on average, radiate the same amount of energy back to space. Because the Earth is much colder than the Sun, it radiates at much longer wavelengths, primarily in the infrared part of the spectrum, which you sense as heat. Much of this heat or thermal radiation emitted by the land and ocean is absorbed by the atmosphere, including clouds. It is then reradiated back to Earth. This is called the greenhouse effect, and it makes life on Earth as we know it possible. However, human activities, primarily the burning of fossil fuels and clearing of forests, have greatly intensified the natural greenhouse effect, causing global warming.
Global Warming Potential
(GWP) = 1.
Last thousands of years in atmosphere.
GWP = 28-36 times that of CO2.
Lasts about a decade on average.
GWP = 265-298 times that of CO2. Lasts for more than 100 years.
GWP = 23,000 times that of CO2. Lasts for thousands of years.
Earth's atmospheric air
Source: http://www.eoearth.org/view/article/170977/
Published: April 2, 2014, 2:56 pm
Author: Milton Beychok
Topic Editor: C Michael Hogan
The Earth's atmospheric air is a colorless, odorless and tasteless mixture of gases consisting mostly of nitrogen (N2) and oxygen (O2). It is the part of Earth's atmosphere that humans and all other animals breathe in order to obtain the oxygen needed to sustain life.
The Earth's atmosphere not only contains the air we breathe, it also holds clouds of moisture (water vapor) that become the water we drink. Furthermore, it protects us from meteors and harmful solar radiation and warms the Earth's surface by heat retention. In effect, the atmosphere is an envelope that protects all life on Earth.
The air may contain pollutants that originate from a variety of sources such as our industries and our vehicles, and can directly or indirectly affect our health and the natural environment. These effects may be experienced near the sources of air pollution and some air pollutants may be transported long distances by the wind, even across political boundaries.
Composition of the atmospheric airThe adjacent table lists the concentration of fourteen gases present in filtered dry air. Two of the gases, nitrogen and oxygen make up 99.03 percent of the clean, dry air. The other listed gases total to 0.97 percent.
Note the amounts of greenhouse gases that are present: water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Additional gases (not listed in the table) are also present in very minute amounts.
The atmospheric air is rarely, if ever, dry. Water vapor is nearly always present up to about 4% of the total volume. In the desert regions, when dry winds are blowing, the water vapor content will be near zero. This climbs to near three percent on extremely hot/humid days. The upper limit of four percent is for tropical climates.
Unfiltered air contains minute amounts of various types of particulate matter derived from sources such as dust, pollen and spores, sea spray, volcanoes, meteoroids and industrial activities.
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A blanket around the Earth
A layer of greenhouse gases – primarily water vapor, and including much smaller amounts of carbon dioxide, methane and nitrous oxide – acts as a thermal blanket for the Earth, absorbing heat and warming the surface to a life-supporting average of 59 degrees Fahrenheit (15 degrees Celsius).
Most climate scientists agree the main cause of the current global warming trend is human expansion of the "greenhouse effect"1 — warming that results when the atmosphere traps heat radiating from Earth toward space.
Certain gases in the atmosphere block heat from escaping. Long-lived gases that remain semi-permanently in the atmosphere and do not respond physically or chemically to changes in temperature are described as "forcing" climate change. Gases, such as water vapor, which respond physically or chemically to changes in temperature are seen as "feedbacks."
Gases that contribute to the greenhouse effect include:
Not enough greenhouse effect: The planet Mars has a very thin atmosphere, nearly all carbon dioxide. Because of the low atmospheric pressure, and with little to no methane or water vapor to reinforce the weak greenhouse effect, Mars has a largely frozen surface that shows no evidence of life.
Too much greenhouse effect: The atmosphere of Venus, like Mars, is nearly all carbon dioxide. But Venus has about 300 times as much carbon dioxide in its atmosphere as Earth and Mars do, producing a runaway greenhouse effect and a surface temperature hot enough to melt lead.
On Earth, human activities are changing the natural greenhouse. Over the last century the burning of fossil fuels like coal and oil has increased the concentration of atmospheric carbon dioxide (CO2). This happens because the coal or oil burning process combines carbon with oxygen in the air to make CO2. To a lesser extent, the clearing of land for agriculture, industry, and other human activities have increased concentrations of greenhouse gases.
The consequences of changing the natural atmospheric greenhouse are difficult to predict, but certain effects seem likely:
The role of human activity
In its Fourth Assessment Report, the Intergovernmental Panel on Climate Change, a group of 1,300 independent scientific experts from countries all over the world under the auspices of the United Nations, concluded there's a more than 90 percent probability that human activities over the past 250 years have warmed our planet.
The industrial activities that our modern civilization depends upon have raised atmospheric carbon dioxide levels from 280 parts per million to 379 parts per million in the last 150 years. The panel also concluded there's a better than 90 percent probability that human-produced greenhouse gases such as carbon dioxide, methane and nitrous oxide have caused much of the observed increase in Earth's temperatures over the past 50 years.
They said the rate of increase in global warming due to these gases is very likely to be unprecedented within the past 10,000 years or more. The panel's full Summary for Policymakers report is online at http://www.ipcc.ch/pdf/assessment-report/ar4/syr/ar4_syr_spm.pdf.
Solar irradiance
It's reasonable to assume that changes in the sun's energy output would cause the climate to change, since the sun is the fundamental source of energy that drives our climate system.
Indeed, studies show that solar variability has played a role in past climate changes. For example, a decrease in solar activity is thought to have triggered the Little Ice Age between approximately 1650 and 1850, when Greenland was largely cut off by ice from 1410 to the 1720s and glaciers advanced in the Alps.
But several lines of evidence show that current global warming cannot be explained by changes in energy from the sun:
References
United States Global Change Research Program, "Global Climate Change Impacts in the United States," Cambridge University Press, 2009
Naomi Oreskes, "The Scientific Consensus on Climate Change," Science 3 December 2004: Vol. 306 no. 5702 p. 1686 DOI: 10.1126/science.1103618
Judith Lean, “Cycles and trends in solar irradiance and climate,” Wiley Interdisciplinary Reviews: Climate Change, vol. 1, January/February 2010, 111-122.
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Principle 5c
Water Vapor is the Most Abundant Greenhouse
Gas
Water vapor is the most abundant greenhouse gas, but it’s role is complex. As water vapor increases, the Earth's atmosphere warms, but so does the possibility of clouds and precipitation.
In the humid equatorial regions, there is a lot of water vapor in the air and so the greenhouse effect is very large. And so adding a small additional amount of CO2 or water vapor has only a small direct impact on global warming.
However, in the cold, dry polar regions (where there is very little water vapor in the air), the effect of a small increase in CO2 or water vapor is much greater. It is true that adding more of a greenhouse gas, such as CO2, to the atmosphere intensifies the greenhouse effect and warms the Earth’s climate. But the amount of warming depends. Read more…
Water Vapor is the Most Abundant Greenhouse
Gas
Water vapor is the most abundant greenhouse gas, but it’s role is complex. As water vapor increases, the Earth's atmosphere warms, but so does the possibility of clouds and precipitation.
In the humid equatorial regions, there is a lot of water vapor in the air and so the greenhouse effect is very large. And so adding a small additional amount of CO2 or water vapor has only a small direct impact on global warming.
However, in the cold, dry polar regions (where there is very little water vapor in the air), the effect of a small increase in CO2 or water vapor is much greater. It is true that adding more of a greenhouse gas, such as CO2, to the atmosphere intensifies the greenhouse effect and warms the Earth’s climate. But the amount of warming depends.
For example, as the atmosphere warms due to rising levels of greenhouse gases, its concentration of water vapor increases, further intensifying the greenhouse effect. This in turn causes more warming, which causes an additional increase in water vapor, in a self-reinforcing cycle, or what’s called a positive feedback loop. This water-vapor feedback loop may be strong enough to approximately double the increase in the greenhouse effect due to the added CO2 alone. The graphic above shows this how this feedback loop works.
Additional important feedback mechanisms involve clouds. Clouds are effective at absorbing the warmth being radiated from the Earth and therefore they exert a large greenhouse effect.
But clouds are also effective at reflecting away incoming solar radiation, thus cooling the Earth. So a change in almost any aspect of clouds, such as their type, location, water content, cloud altitude, particle size and shape, or lifetimes, affects the degree to which clouds warm or cool the Earth. Some changes amplify warming while others diminish it. Scientists are trying hard to better understand how clouds change in response to climate warming, and how these changes affect our climate through various feedback mechanisms.
click the image to enlarge
Water Vapor and the Climate
Source: http://www.acs.org/content/acs/en/climatescience/climatesciencenarratives
On average, water vapor probably accounts for about 60% of the global warming effect caused by greenhouse gases. However, water vapor does not control the Earth’s temperature, but is instead controlled by the temperature. This is because the temperature of the surrounding atmosphere limits the maximum amount of water vapor the atmosphere can contain. If a volume of air contains its maximum amount of water vapor and the temperature is decreased, some of the water vapor will condense to form liquid water. This is why clouds form as warm air containing water vapor rises and cools at higher altitudes where the water condenses to the tiny droplets that make up clouds.
The greenhouse effect that has maintained the Earth’s temperature at a level warm enough for human civilization to develop over the past several millennia is controlled by a handful of gases, mainly carbon dioxide, CO2, with smaller contributions from methane, CH4, nitrous oxide, N2O, and ozone, O3. Since the middle of the 20th century, small amounts of man-made gases, mostly chlorine- and fluorine-containing solvents and refrigerants, have been added to the mix. The atmosphere can pack in much more of these gases than water vapor. Thus, CO2 (as well as CH4, N2O, and O3) has been building up in the atmosphere since the Industrial Revolution when we began burning large amounts of fossil fuel.
If there had been no increase in the amounts of these greenhouse gases, the amount of water vapor in the atmosphere would not have changed. The addition of the greenhouse gases causes the temperature to increase and this leads to an increase in water vapor that further increases the temperature. This is an example of a positive feedback effect. The warming due to increasing greenhouse gases causes more water vapor to enter the atmosphere, which adds to the warming effect of the of the greenhouse gases.
There is also a possibility that adding more water vapor to the atmosphere could produce a negative feedback effect. This could happen if more water vapor leads to more cloud formation. Clouds reflect sunlight and reduce the amount of energy that reaches the Earth’s surface to warm it. If the amount of solar warming decreases, then the temperature of the Earth would decrease. In that case, the effect of adding more water vapor would be cooling rather than warming. But cloud cover does mean more condensed water in the atmosphere, making for a stronger greenhouse effect than non-condensed water vapor alone – it is warmer on a cloudy winter day than on a clear one. Thus the possible positive and negative feedbacks associated with increased water vapor complicate matters. The actual balance between them is an active area of climate science research.
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Principle 5d
The Two Most Important Greenhouse Gases: CO2 and Methane
By now you know that greenhouse gases include carbon dioxide, methane, nitrous oxide and other gases that accumulate in the atmosphere and create what is in effect a blanket around the Earth—a heat-reflective layer that keeps the Earth at a livable temperature. These gases form the insulation that keeps the planet warm enough to support life. But when increased, as is happening now by the burning of fossil fuels like coal, oil, and gas, they can heat up the planet and cause a host of climate-related environmental problems. Read more…
The Two Most Important Greenhouse Gases: CO2 and Methane
By now you know that greenhouse gases include carbon dioxide, methane, nitrous oxide and other gases that accumulate in the atmosphere and create what is in effect a blanket around the Earth—a heat-reflective layer that keeps the Earth at a livable temperature. These gases form the insulation that keeps the planet warm enough to support life. But when increased, as is happening now by the burning of fossil fuels like coal, oil, and gas, they can heat up the planet and cause a host of climate-related environmental problems.
Two of these gases are most worrisome:
- Carbon dioxide is released whenever coal, oil, natural gas and other carbon-rich fossil fuels are burned. Although carbon dioxide is not the most powerful greenhouse gas, it is the largest contributor to climate change because it is so common. In order to reduce carbon dioxide emissions, we need to reduce the amount of fossil fuels we use in our cars, homes, and lives by shifting to renewables.
- Methane is caused by the decomposition of plant matter and is released from landfills, swamps, and rice paddies. Cattle also release methane. Although methane emissions are lower than carbon dioxide emissions, it is considered a major greenhouse gas because each methane molecule has 25 times the global warming potential of a carbon dioxide molecule.
watch the movie to see how CO2 moves around the earth
Methane vs. Carbon Dioxide: A Greenhouse Gas Showdown
Source: http://www.onegreenplanet.org/animalsandnature/methane-vs-carbon-dioxide-a-greenhouse-gas-showdown/
How Much Carbon Dioxide in the Atmosphere Versus Methane?
Carbon Dioxide
According to the EPA’s overview of greenhouse gases, carbon dioxide (CO2) accounts for about 82 percent of all greenhouse gas emissions from human activities in the U.S. Since the industrial revolution, human activities have been altering the carbon cycle in the atmosphere by adding more CO2 and influencing the ability of “natural sinks”, like forests, to remove CO2 from the atmosphere.
Methane
Though it is the second most prevalent greenhouse gas emitted by human activities in the U.S., methane only accounts for nine percent of total greenhouse gas emissions. It is nevertheless a huge part of the equation. Like CO2, there are natural processes that remove methane from the atmosphere, but these can no longer keep up with the amount produced.
Where Do These Emissions Come From?
Carbon Dioxide
Of the processes that emit carbon dioxide, electricity and transportation account for 70 percent of emissions in the U.S. The combustion of fossil fuels is the chief culprit. Additional sources include industry, residential and commercial activities – again connected with fossil fuel combustion – while about six percent is produced by non-fossil fuel combustion.
As it stands now, only about 15 percent of the CO2 produced is being offset by forests. And to make matters worse, deforestation is causing millions of hectares of carbon trapping trees to be destroyed every year, releasing billions of tons of CO2 into the atmosphere and contributing as much as 25 percent to the causes of global warming.
Methane
In the U.S., methane emissions come primarily from industry, natural gas and petroleum systems; and from agriculture, respiratory and digestive emissions from livestock and manure management. An important additional source is landfills. However, across the globe it’s the agricultural sector that is more decidedly the primary source of methane emissions.
Between 1990 and 2012, methane emissions in the U.S. decreased by about 11 percent because of decreased exploration of natural gas and petroleum within the country, but emissions from animal agriculture still increased.
Global Warming Potential
This is where the showdown gets intense. Global Warming Potential (GWP) is a measure created by the EPA. It represents how well a gas absorbs heat or, in other words, how long a gas sticks around to warm the earth. GWP is measured relative to carbon dioxide over a particular period of time, usually 100 years.
Carbon Dioxide
In a hundred year period, the GWP of CO2 is measured by the EPA as one, while all other gases are measured relative to this. According to the World Preservation Foundation, the problem with focusing climate change mitigation strategies on carbon dioxide is that it has such a long lifespan in the atmosphere, taking many decades and even centuries to leave. This means that any reduction today may lower future heating, but it will not result in the rapid cooling that is needed in the present.
Methane
Here’s the kicker: methane, the gas produced extensively by the livestock industry worldwide, traps up to 100 times more heat in the atmosphere than carbon dioxide within a 5 year period, and 72 times more within a 20 year period. The good news is that methane also leaves the atmosphere within a decade. This makes for a short-lived, but intense climate changer.
So methane warms the planet rapidly, but it dissipates from the atmosphere more quickly than carbon dioxide. According the EPA, the GWP of methane is 21, which indicates its effect over a 100 year period. A 2009 report published by The World Watch Institute stressed that the more relevant GWP figure is 72, since it’s within the next 20 years that we desperately need to act to stop climate change before a domino effect is initiated and our imbalanced bio-systems spiral out of livable conditions.
So What Does This Mean?
Focusing on carbon emissions is only half the battle – or 74 percent of total emissions to be exact – but, focusing on the percentage of total emissions is extremely misleading because it ignores global warming potential altogether.
We’ve seen that methane, which accounts for only 14 percent of emissions worldwide, traps up to 100 times more heat than carbon dioxide over a 5-year period. This means that even though carbon dioxide molecules outnumber methane 5 to 1, this comparatively smaller amount of methane is still 19 times greater a problem for climate change over a 5 year period, and 4 times greater over a 100 year period.
To put it another way, any methane molecule released today is 100 times more heat-trapping than a molecule of carbon dioxide, or potentially even higher according to NASA’s Goddard Institute for Space Studies.
With the UN establishing various tipping points for irreversible climate change damage on the horizon, it’s time that methane enters mainstream consideration.
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Methane and Frozen Ground
Source: https://nsidc.org/cryosphere/frozenground/methane.html
Kevin Schaefer is a permafrost scientist at NSIDC. He studies the carbon cycle, or the processes by which the Earth's carbon moves around: from the air into plants, from plants into the ground, and then back into the air (Figure 2). Dr. Schaefer studies the carbon that is frozen deep in Arctic permafrost. As the Earth warms, scientists worry that some of the carbon in permafrost could escape to the atmosphere as carbon dioxide or methane. Increasing the amount of these gases in the atmosphere could make Earth's climate warm up even more.
Here Dr. Schaefer provides some answers to questions about methane and frozen ground.
What is methane?
Methane is a gas made up of one carbon atom and four hydrogen atoms. It's the same natural gas that some people use to heat their homes, and it also exists naturally in the atmosphere. Scientists worry that if methane increases in the atmosphere, it could cause even more warming than carbon dioxide from the burning of fossil fuels. Although there is much less methane in the atmosphere than carbon dioxide, it traps heat about twenty times as efficiently as carbon dioxide.
What are the sources of methane in the Arctic?
There are two potential sources of methane in the Arctic. The first source of methane is called methyl clathrate. Methyl clathrates are molecules of methane that are frozen into ice crystals. They can form deep in the Earth or underwater, but it takes very special conditions, with high pressure and low temperature, to make them. If the temperature or pressure changes, the ice that imprisons the methane will break apart, and the methane will escape. We're not sure how much methane is trapped in methyl clathrates, or how much is in danger of escaping.
The other major source of methane in the Arctic is the organic matter frozen in permafrost. This is the source of methane that I study. The organic matter in permafrost contains a lot of carbon. It is made of dead plants and animals that have been frozen deep in permafrost for thousands of years. As long as this organic matter remains frozen, it will stay in the permafrost. However, if it thaws, it will decay, releasing carbon dioxide or methane into the atmosphere. This is why permafrost carbon is important to climate study.
Figure 2. Carbon moves through the Earth's atmosphere, oceans, and land in a process called the carbon cycle.
—Credit: NSIDC, modified from NASA Earth Science Enterprise
How did this carbon get into permafrost in the first place?
Carbon was buried in permafrost by processes that took thousands of years. During the last ice age, great ice sheets covered most of the continents. As they spread out and then shrunk back, the heavy fields of ice ground up the rock underneath them into a very fine dust called loess or glacial flour. The ice sheets produced a huge amount of this powdered rock, and wind and rain deposited it onto the soil.
As the ice sheets added loess to the soil, the soil got thicker. As the soil built up, the active layer on top stayed the same thickness. The active layer freezes and thaws each year, and plants can grow in it. But underneath the active layer, roots and other organic matter were frozen into the permafrost, where they can't decay.
Most of the organic matter consists of partially decayed roots, whole roots, and other plant material. However, there are also animals and animal material frozen in the ground--sometimes people find entire mastodons or other animals frozen in the permafrost (Figure 3). Significant deposits of carbon-rich permafrost, or yedoma, have been found in Russia.
How much carbon is stored in frozen ground?
There is a huge amount of carbon stored in permafrost. Right now, the Earth's atmosphere contains about 850 gigatons of carbon. (A gigaton is one billion tons—about the weight of one hundred thousand school buses). We estimate that there are about 1,400 gigatons of carbon frozen in permafrost. So the carbon frozen in permafrost is greater than the amount of carbon that is already in the atmosphere today. That doesn't mean that all of the carbon will decay and end up in the atmosphere. The trick is to find out how much of the frozen carbon is going to decay, how fast, and where.
Figure 3. This steppe bison lay frozen in permafrost for 36,000 years before its discovery in 1979. The bison, known as "Babe," is on display at the University of Alaska, Fairbanks Museum of the North.
—Credit: Photo by Bill Schmoker (PolarTREC 2010), Courtesy of ARCUS
What will happen to the frozen carbon if permafrost thaws?
When permafrost thaws, the frozen organic matter inside it will thaw out, too, and begin to decay. It's like taking a bag of frozen broccoli out of the freezer and putting it into the refrigerator. Once it thaws, it will eventually decay and break down.
As organic matter decays, it gets eaten up and digested by microbes. The bacteria that eat it produce either carbon dioxide or methane as waste. If there is oxygen available, the microbes make carbon dioxide. But if there is no oxygen available, they make methane. Most of the places where methane would form are the swamps and wetlands. And there are many miles of wetlands in the Arctic. When you walk around in the Arctic tundra, it's like sloshing through a giant sponge.
When permafrost carbon turns into methane, it bubbles up through soil and water. On the way, other microorganisms eat some of it. But some methane makes it to the surface and escapes into the air.
How will additional methane from permafrost affect global warming?
There are several opposing processes at work, which make this a hard question to answer. Warmer temperatures mean that permafrost can thaw and release methane to the atmosphere. But warming also means that the growing seasons in Arctic latitudes will last longer. When the growing season is longer, plants have more time to suck up carbon from the atmosphere. Since carbon in the air is what plants use to grow, it can also act as a sort of fertilizer under certain conditions. Then plants to grow faster and take up even more carbon. Right now, the Arctic takes up more carbon than it releases. This means that plants take up carbon during the growing season, but do not release as much carbon through decay. So we say that the Arctic acts as a carbon sink.
But if the Earth continues to warm, and a lot of permafrost thaws out, the Arctic could become an overall source of carbon to the atmosphere, instead of a sink. This is what scientists refer to as a "tipping point." We say that something has reached a tipping point when it switches from a relatively stable state to an unstoppable cycle. In this case, the Arctic would change from a carbon sink to a carbon source. If the Arctic permafrost releases more carbon than it absorbs, it would start a cycle where the extra carbon in the atmosphere leads to increased warming. The increased warming means more permafrost thawing and methane release.
What are the questions that scientists are currently studying about permafrost and methane?
The big questions are: How much carbon is currently frozen in permafrost? How much will thaw out in the future and when will it be released into the atmosphere? We also want to know how much carbon could be released as methane, and how much could be released as carbon dioxide. That's related to how much of the land is wetlands, since ponds and lakes and swamps are the main places that will produce methane.
If governments around the world knew how much methane could be released from permafrost, it could help them decide what to do about it. For example, they would know how much we need to reduce fossil fuel emissions from human activities. They would also need to know how much carbon the Earth is emitting on its own.
The good news is that we haven't reached the tipping point yet. People in some areas have reported that some permafrost carbon has already started to decay. But measurements of carbon dioxide in the air show the Arctic is still a carbon sink. So we are studying permafrost to understand more about how it acts. We are also trying to measure how much carbon there is and where is it located. Then scientists can use that information in computer programs that help us better plan for the future.
Q
Scientists Discover a New Source of Methane: Tree Trunks
http://e360.yale.edu/digest/scientists-discover-a-new-source-of-methane-tree-trunks
April 3, 2017
Forests have long been seen as important sinks, or storage sites, for greenhouse gases. But scientists recently discovered that tree trunks emit methane, a powerful greenhouse gas at least 25 times more potent than carbon dioxide in the short-term.
The discovery comes from researchers at the University of Delaware, who measured methane output from soils, individual trees, and decomposing woody biomass lying on a forest floor in northeast Maryland over a 10-month period.
Using a mobile greenhouse gas analyzer, the University of Delaware researchers found that while forest soils suck up and store methane, tree trunks actually release the gas. They also found that different tree species release it at different rates. One theory they posed was that internal rotting or infection inside the tree trunk could cause the methane leaks. The findings were published recently in the journal Ecosystems.
“When people develop ecosystem to global-scale methane budgets, there’s always a chunk in which it is uncertain from where that methane is coming,” said University of Delaware doctoral student Daniel Warner, lead author of the study, in a statement. “Methane emissions by vegetation and tree trunks are seen as a newly considered source that might bring that budget closer to our estimates.”
Q
Principle 5e
Natural Processes Cannot Explain Recent Rapid Changes in Earth’s Climate
Natural processes driving changes in the Earth’s climate do not explain the rapid climate change observed in recent decades. The only explanation that is consistent with all available evidence is that human impacts are playing an increasing role in climate change. Future changes in climate are very rapid compared to historical changes.
Read more…
Natural Processes Cannot Explain Recent Rapid Changes in Earth’s Climate
Natural processes driving changes in the Earth’s climate do not explain the rapid climate change observed in recent decades. The only explanation that is consistent with all available evidence is that human impacts are playing an increasing role in climate change. Future changes in climate are very rapid compared to historical changes.
In the past century alone, the temperature has climbed 0.7 degrees Celsius, roughly ten times faster than the average rate of ice-age-recovery warming. (See the interesting chart below to get a sense of the speed of temperature change.)
Models predict that Earth will warm between 2 and 6 degrees Celsius in the next century. When global warming has happened at various times in the past two million years, it has taken the planet about 5,000 years to warm 5 degrees. The predicted rate of warming for the next century is at least 20 times faster. This rate of change is extremely unusual, and it will be extremely hard for animals and plants to adjust. It is likely that many will not be able to and will simply go extinct.
The steady rise of Earth’s temperature as greenhouse gases accumulate in the atmosphere and trap more and more heat is sending the planet spiraling closer to the point where warming’s catastrophic consequences may be all but assured. That metaphoric spiral has become a literal one in this graphic drawn up by Ed Hawkins, a climate scientist at the University of Reading in the United Kingdom. The animated graphic features a rainbow-colored record of global temperatures spinning outward from the late 19th century to the present as the Earth heats up. The graphic displays monthly global temperature data from the U.K. Met Office and charts how each month compares to the average for the same period from 1850-1900, the same baselines used in the most recent report from the Intergovernmental Panel on Climate Change. At first, the years vacillate inward and outward, showing that a clear warming signal had yet to emerge from the natural fluctuations that happen from year to year. But clear warming trends are present in the early and late 20th century.
Principle 5f
Local Relevance
Explore Greenhouse Gas (GHG) Emissions from Large Facilities in Your State: An Interactive Tool
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Principle 5g
Misconceptions about this Principle
The Misconception
Isn’t it true that water vapor is the most powerful greenhouse gas? If water vapor is the most powerful, why are we so worried about CO2.
The misconception or myth goes something like this: “Water vapor is the most important greenhouse gas. If you get a fall evening or spring evening and the sky is clear, the heat will escape and the temperature will drop and you get frost. If there is a cloud cover, the heat is trapped by water vapor as a greenhouse gas and the temperature stays quite warm.”
The Science
Water vapor creates what scientists call a 'positive feedback loop' in the atmosphere greatly amplifying the impact CO2 has on global warming.
The science says: when climate change deniers use this argument, they are trying to imply that an increase in CO2 isn't a major problem. If CO2 isn't as powerful as water vapor, which there's already a lot of, adding a little more CO2 couldn't be that bad, right? What this argument misses is the fact that water vapor creates what scientists call a 'positive feedback loop' in the atmosphere — making any temperature changes larger than they would be otherwise. Read more…
Source: http://www.skepticalscience.com
The Science
Water vapor creates what scientists call a 'positive feedback loop' in the atmosphere greatly amplifying the impact CO2 has on global warming.
The science says: when climate change deniers use this argument, they are trying to imply that an increase in CO2 isn't a major problem. If CO2 isn't as powerful as water vapor, which there's already a lot of, adding a little more CO2 couldn't be that bad, right? What this argument misses is the fact that water vapor creates what scientists call a 'positive feedback loop' in the atmosphere — making any temperature changes larger than they would be otherwise.
How does this work? The amount of water vapor in the atmosphere exists in direct relation to the temperature. If you increase the temperature, more water evaporates and becomes vapor, and vice versa. So when something else causes a temperature increase (such as extra CO2 from fossil fuels), more water evaporates. Then, since water vapor is a greenhouse gas, this additional water vapor causes the temperature to go up even further—a positive feedback loop.
How much does water vapor amplify CO2 warming? Studies show that water-vapor feedback roughly doubles the amount of warming caused by CO2. So if there is a 1°C change caused by CO2, the water vapor will cause the temperature to go up another 1°C. When other feedback loops are included, the total warming from a potential 1°C change caused by CO2 is, in reality, as much as 3°C.
The other factor to consider is that water is evaporated from the land and sea and falls as rain or snow all the time. Thus the amount held in the atmosphere as water vapor varies greatly in just hours and days as result of the prevailing weather in any location. So even though water vapor is the greatest greenhouse gas, it is relatively short-lived. On the other hand, CO2 is removed from the air by natural geological-scale processes and these take a very long time to work.
Consequently CO2 stays in our atmosphere for years and even centuries. A small additional amount has a much more long-term effect.
So skeptics are right in saying that water vapor is the dominant greenhouse gas. What they don't mention is that the water vapor feedback loop actually makes temperature changes caused by CO2 even bigger.
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