What are the basics of Global Warming, specifically the impact of extra heat? What is extra heat? What is its impact on global warming? Feel free to make comments if you see things differently!
1. Natural Heat versus Extra Heat
The sun heats up Earth during the day. This solar energy constitutes natural heat, as opposed to extra heat that is added by human activity such as burning of fossil fuels. Simply said, extra heat comes on top of heat that comes naturally.
Sunlight reaches Earth with a strength of 174 PW or about 1.7 billion times the amount of power produced by a large electric power plant (which is some 100 million watts of energy). That is indeed a huge amount of power compared to the total human energy production, which was only 13.5 TW in 2001.
However, all this sunlight is needed to lift Earth's temperature all the way from the minus 454 degrees Fahrenheit (3 degrees Kelvin) of deep space to its current average temperature. In other words, it takes just a little bit of extra heat by comparison to increase the average temperature on Earth by a few degrees.
Also, we get a different impression if we look at the amount of energy deposited by the Sun per square meter. At the top of the atmosphere, the shortwave energy flux received from the Sun is about 1,368 watts per square meter. Because of its spherical shape, at any instant the Earth receives on average only half the incident solar flux, i.e. 684 W/m² . Due to the Earth's rotation, the average radiative flux received over a day-night cycle is half of this value, i.e. 342 W/m² .
Taking into account cloud coverage and the fact that the efficiency rate of capturing this energy with solar panels is rather low (say 10% to 15%), you can only expect an output of 19 to 56 W/m² or 0.45 - 1.35 (kW·h/m²)/day from solar panels.
How much extra heat is generated by human activity, compared to the heat resulting from sunlight? Firstly, the human body itself creates a lot of heat, but let not count that as "extra" heat for the time being. We're mainly looking at industrial activity, using electricity, cars and the like. A house will consume about 1kWe (kilowatt-electric) if measured as a continuous stream of electric power. If you keep the lights on in your office and your house, you may be using a few hundred watts of energy. A TV-set or a computer may use much more. If you drive home in your car, the engine generates a huge amount of heat. Vacuum cleaners, air-conditioners and refridgerators also use huge amounts, but they're not used continuously. On average, a typical person adds a few hundred watts of energy into the atmosphere, day and night, all year long. Currently, most of this demand is met by burning fossil fuel, which counts as extra heat that is added to the atmosphere.
As said, total human energy production was 13.5 TW in 2001. Since total Earth surface is 510,100,000 km2, the extra heat works out to be some 0.02 W/m², so it's rather insignificant when spread out over the entire globe.
2. The Greenhouse Effect and Global Warming
The atmosphere works like a greenhouse, shielding us from too much sunshine during the day, while also keeping heat trapped so that we do not freeze at night. In other words, the greenhouse effect shields us from both extremely high and low temperatures.
Greenhouse gases such as methane and carbon dioxide, as well as water vapor, trap such heat in Earth's atmosphere. The more greenhouse gases are released into the atmosphere, the stronger the greenhouse effect.
As said, activities such as burning of fossil fuels add extra greenhouse gases into the atmosphere, resulting in a stronger greenhouse effect. This will both result in both less sunshine getting through and less heat escaping the atmosphere, but the combined effect is a relatively higher overall temperature on Earth. Over the years, human activity, specifically burning fossil fuels, has substantially increased the amount of carbon dioxide in the atmosphere, resulting in a stronger greenhouse effect, causing global warming and climate change.
3. Positive Feedback
This global warming comes with positive feedback, i.e. the impact of global warming itself accelerates global warming and causes further increase of temperatures:
- Decreased reflection of sunlight results in increased retention of heat. The overall albedo (reflection rate) of Earth will decrease. Sunlight is reflected more by white surface (such as snow), compared to darker surface (such as rock and soil). As the albedo decreases (which is the case when snow melts), less light is reflected and more heat is absorbed by the soil. Albedos can be as high as 90% for snow and as low as 4% for charcoal. Most land areas have an albedo range of 10 to 40%. The average albedo of the Earth is about 30%. As the permafrost, the ice and snow in the polar regions melts, as the iceplates in the Arctic regions break loose and icebergs float away, as less snow falls in the mountains and as glaciers melt, all these areas change color from white to dark. All this causes a further rise in temperature, as the darker soil and sea absorb more sunlight and thus heat up, where previously the sunlight was reflected back into space by the white ice and snow.
- As the permafrost melts and disappears, thawing boreal forests, swamps and tundras will emerge that - as bogs heat up and peat thaws - will release huge amounts of methane gas, a twenty times more powerful greenhouse gas than carbon dioxide.
- Global warming will come with more extreme weather conditions. Floods typically cause a huge loss of top-soil. Rotting and decomposing trees release methane, as do the termites that feed on them. Land clearing, over-grazing, droughts and fires further put entire regions at risk of desertification. The Amazon rainforest, the African tropics, the tropical rainforests in Indonesia, they all risk turning into savannah and deserts, releasing the carbon stored in trees as carbon dioxide into the air and releasing huge amounts of methane in the process, while also decreasing the capacity of soil to absorb carbon dioxide.
- As snow melts, more humidity gets into the air. This vapor constitutes another important greenhouse gas. As Earth heats up, the amount of water vapor in the atmosphere will increase, as more water evaporates at the surface, both on land and at sea. This causes a further increase in the greenhouse effect and thus a further increase in atmospheric temperature.
- The human factor also constitutes an important form of positive feedback that's often overlooked by climatologists. More extreme weather conditions can be expected, i.e. droughts followed by floods and storms, followed again by droughts, etc. This will result in larger run-off of fertile top-soil. Farmers may try to adapt to climate change, but it will take years before they will have found the best types of plants for the new conditions. The result will be higher food prices and demand for new agricultural areas. Rising sea levels, droughts, storms and floods will make people leave low-lying coastal areas and move to higher grounds, where they will start clearing trees for agriculture, industry, roads and housing. The overall result will be increased loss of forests. Thus, the human factor is expected to constitute another positive feedback, as discussed further in the Ten Dangers of Global Warming.
In other words, Global warming comes with 'positive feedback', which means that we're not only stuck with global warming for some time to come, but we can only expect things to get worse, even if we did decide to stop adding any further greenhouse gases and extra heat (i.e. on top of the heat and gases that come naturally).
4. Impact of Extra Heat
All extra heat that we release will add to global warming. As said, it seems rather insignificant compared to natural heat from the sun, from geysers and other natural geo-thermal sources. It also seems insignificant compared to the natural heat that remains trapped in the atmosphere due to the extra amounts of greenhouse gasses we produce. Neverthless, as more heat remains trapped in the atmosphere due to an accelerating greenhouse effect (since global warming comes with all kinds of positive feedback), its significance is increasing. Extra heat may become increasingly important in assessments, e.g. when subsidies are allocated to the type of energy that produce the least extra heat.
5. Nature versus Human Activity
In many respects, human activity is to blame for global warming. Burning of oil and coal are obvious human activities that result in global warming. While nuclear power plants may look better in terms of greenhouse gases compared to burning of fossil fuels, nuclear plants will also directly add extra heat into the atmosphere. In the light of the accelerated greenhouse effect, such extra heat remains - even more than before - trapped in the atmosphere, adding further acceleration to the already accelerating global warming. As said, extra heat may seem insignificant compared to natural heat, but it may just tip the balance when deciding how to allocate subsidies to combat global warming. Similarly, where geothermal schemes extract heat from the depths of Earth, this may also constitute extra heat that wouldn't be added naturally.
Agriculture can also add substantial amounts of extra heat: animals release methane gas, clearing land for agriculture by burning forests releases carbon dioxide, inefficient farming practices result in release of nitrous oxide, etc. In Australia, greenhouse gas emissions from agriculture constituted 16% of total emissions in 2004 (source), while agriculture was largest source of nitrous oxide and methane emissions (source).
But that doesn't mean that all human activity was bad and that all farms needed to be transformed into forest overnight. Bad forestry practies also add extra greenhouse gases, due to composting and formation of swamps resulting in methane, and due to natural burning and firestorms. Many forests would burn naturally and this can be minimised with good forestry management. Similarly, termites release methane gasses, so it makes sense to avoid this.
Banning all human activity and letting nature go rampant is not the answer. The big challenge is to find ways in which we can live, work, travel and do things we want to do while minimising our contributions to further global warming. Capturing the heat of the sun and geysers, and capturing the turbulance of wind, waves and rivers is not only a way to use energy that is already present naturally, it can also flatten wild weather patterns that could do a lot of damage.
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Comments: 9
billyshull@msn.com In the subject line put "4 planet earth" or it will not be opened. I will respond with the same subject line
On these quotes I will comment.
"Firstly, the human body itself creates a lot of heat, but let not count that as "extra" heat for the time being. We're mainly looking at industrial activity, using electricity, cars and the like"
"In other words, it takes just a little bit of extra heat by comparison to increase the average temperature on Earth by a few degrees."
"Due to the Earth's rotation, the average radiative flux received over a day-night cycle is half of this value, i.e. 342 W/m²".
"As said, total human energy production was 13.5 TW in 2001. Since total Earth surface is 510,100,000 km2, the extra heat works out to be some 0.02 W/m², so it's rather insignificant when spread out over the entire globe."
Comment
That you not count the heat produced by the human body as "extra heat", is fair with me. But that you only look at industrial activity is questionable. In my country there are as many pigs as human beings. Then there are dogs, sheep, cows, chickens and whatsoever. They also produce heat and are a product of human activity. Furthermore, there are many people that heat there houses on wood to reduce costs. Globally there will be millions of people heating or cooking on wood. Whole forests are burned to turn them over in agricultural areas. Wasteproducts are often burned. So there is a higher amount of heat production as your estimation.
There is not only heat production as a result of human activity. There is also heatcapturing as a result of that. A waterpower installation captures more radiative flux due to the difference between a streaming river or a quiet artificial lake. In my country a sea is turned into a lake and in that lake they made land. That is also a change in radiative flux. The changing of a forest in agricultural land is a change in radiative flux, not to speak of the possibility of erosion.
Then you say, that the amount of extra heat produced is rather "insignificant" when spread over the entire globe. But twothirth of the earth is water. So the heatproduction is three times as high on land. The total amount of heat is the same, but the effect on aircirculation is a question to me. I observed, that in winter the average temperature in the city was five degrees (Celsius) higher then as measured at the nearby airport (what is given as the regional temperature). Large urban areas are heated 24 hours a day. What is the effect?
The question is not only how much heat is produced, but also how much heat can be lost by the Earth. We live on a sphere. So the surface is much smaller then the content. When we produce heat by human activity, is the surface big enough to get rid of it. If not, the insignificant amount of heat accumulates to maybe the little bit of extra heat "to increase the average temperature on Earth by a few degrees."
I am just a layman and I see my contribution as insignificant, but it is hard to believe for me that such a low concentration of the gas CO2 can have such a devastating effect. And I don't know about a scientific experiment, that proves the theory of heatcapturing of the so called greenhouse gases. A relationship is not the actual proof of causal effect. So can there be an other variable?
Then finally, there is a fundamental question in your comparison. You compare the heat producing energy of the sun with the heat produced by a (part) of human activity. Then you say the later "is insignificant". You don't compare the heat captured by the greenhouse gases in relation to the total amount of heat production by the sun. The question is: "Is the heat production due to human activity insignificant in relation to the heat capturing of greenhouse gases?" I will put it this way:
If the amount of heat production of the sun is a constant over time, what is the contribution of human activity to the raise of Global temperature as a result of the production of greenhouse gases (natural and fossile) and what is the contribution as a result of the production of heat (natural and fossile). This is a fundamental question, while the relative contribution by the production of heat has a influence on the discussion of the use of alternative or "green" or endurable energy. For instance biomass produces as much heat as oil or gas and is no solution fot Global warming, when heat is a more significant factor then you suggest.
Ton van der Linden
Solar intensity has increased since 1750; the IPCC puts radiative forcing resulting from this increase at about +0.12 watts/m².
Ton: "..what is the contribution of human activity to the raise of Global temperature as a result of the production of greenhouse gases
The IPCC puts net antropogenic radiative forcing at about +1.6 watts/m². Most is this results from greenhouse gases, but also mentioned are linear contrails. Since linear contrails had a component value of +0.02 watts/m², you would think it would also be worthwhile looking at extra heat.
http://www.ipcc.ch/pdf/assessment-report/ar4/wg1/ar4-wg1-ts.pdf
Samsam,
Firstly: before we go on with our discussion we have to agree about some basic issues.
What we are talking about is physics. It is an exact science guided by definitions and formulas with an agreed upon notation.
So the IPPC is speaking of RF, that is Radiative Forcing, expressed in the notation W/m² as you prefer.
Definition by IPPC: The RF represents the stratospherically adjusted radiative flux change evaluated at the tropopause, as defined by the TAR.
Apart from exactness is all science guided by logic.
And apart from that is all science based on mutual trust.
That means that I accept the calculations of the IPPS and also your calculations as being gathered in a proper scientific way with the ame to enhance knowledge.
At the same time it means that the interpretation of the gathered data can be discussed on the basis of logical arguments.
If you don't agree, don't read further.
Secondly: superficial scrutiny (my comments are placed in brackets)
The contribution of human activity (the combined anthropogenetic RF) to Global Warming is 1.6 W/m², according to the IPPC. This is likely to be at least five times greater than that due to solar irradiance changes (in contradiction with a later statement, see below, where it is 13 times greater).
The direct RF due to increases in solar irradiance since 1750 is estimated to be 0.12 W/m², with a low level of scientific understanding (7,5% compared to combined anthropogenetic RF).
My comment to you: Ok, that is not a constant and not insignificant, but also not substantial.
The contribution of extra heat is 0.02 W/m² according to you.
That suggests, that this contribution is 1,25% of the total Global Warming effect.
So I gained something, but I still lose. It looks insignificant indeed.
What is the meaning of the new difficult term introduced in the discussion?
IPPC: Persistent linear contrails from aviation contribute an RF of 0.01 Wm2, with a low level of scientific understanding (0,6% of anthropogenetic RF).
My comment: That really is insignificant.
Thirdly: scientific scrutiny
What IPPC tells me.
The total contribution due to human activity is equal to the total contribution due to CO2 (1.6 and 1.66 respectively).
This is because of the fact, that the positive and negative effects of other variables are in balance with each other.
So the other variables together have no effect, contribution 0.
That maybe is surprising, but it makes calculations a lot easier.
The Global mean concentration of CO2 in 2005 was 379 ppm, leading to a RF of 1.66 W/m².
Then there is a very important footnote:
According to the rapport of the IPPC in a footnote all figures of RF are the change in radiative flux over the last 250 years, from 1750 uptill now.
This brings us to a further specification of the definition of RF:
The RF represents the stratospherically adjusted radiative flux change evaluated at the tropopause, as defined by the TAR, over time.
Time is an important factor and we have to reexamine our data.
The contribution of extra heat is 0.02 W/m² according to you. This is a measurement in one year, 2001.
The increase in CO2 RF according to IPPC in the decade from 1995-2005 was 20%. That means that the increase in this period was 0.33 W/m².
Additionally they state that ¾ is due to past emissions of fossil fuels and cement production, ¼ is caused by land use changes.
This means that the rise in CO2 RF in the formentioned decade is 0.25 W/m² due to human industrial activity.
This calculation fits exactly in your definition of "extra heat". So I drop my earlier questions about the narrowness of your definition. On the other hand I feel free to do some calculation with your data. Your calculation is based on one year, the year 2001, which is in the middle of the decade from 1995-2005. So I assume that the figure you found is the average of the decade. Then the contribution of extra heat over the decade is 0.20 W/m².
That means that the total contribution of extra heat due to human industrial activity in the decade 1995-2005 is almost equal to the contribution of the rise in CO2 due to the same industrial activity. That is by now means insignificant.
Fourthly: choice
Now there are two possibilities:
Either you keep with the comparison in your paper, that the contribution of extra heat is insignificant in relation to solar flux. Which logically means that the contribution of the rise in CO2 is also insignificant, because both contributions are almost equal.
Or you change your statement of the contribution of extra heat in the way that it is something less, but almost equal to the contribution of rise in CO2.
Both statements have farreaching consequences as I wrote in my first comment.
Ton van der Linden
PS: There is a Dutch expression when people divide things equally among each other, they say:"We do samsam". Sam is an abbreviation of 'samen', which means 'together'.
As you may have read, I advocate a tax on emissions with the proceeds used to support local supply of better alternatives. I would also like to see both nuclear plants and nuclear weapons banned. Details of what those better alternatives are is best worked out by market mechanisms, but for legal purposes a clear borderline must be set as to which technologies will be supported and which ones not.
The concept extra heat can help out - when used in regulations, it can exclude nuclear plants from support, while giving technologies that do not produce extra heat (such as solar and wind) the support they need.
You change the subject.
I keep your concept.
Thank you,
Ton
According to Stephane Lhomme, spokesman for the French anti-nuclear association Sortir du Nucléare: "Summer 2003 already proved that the promises made by the defenders of nuclear energy are false. Atomic energy is not going to reduce global warming, but -- irony of our climate problems -- that warming does reduce the capacity for utilizing atomic energy,"
http://ipsnews.net/news.asp?idnews=29441
PS: Sambal oelek is a spicy additive to Indonesian food. In Dutch we refer to it as 'sambal'. It makes the food taste hotter. So it is a kind of 'extra heat'. We use it also in Chinese food. Indonesia is a former colonny of the Netherlands (Nederlands Indië or 'Dutch India').
Recently, a story also appeared in New Scientist covering above study under the title Heat we emit could warm the Earth