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Global Warming is the increase of Earth's average surface temperature due to effect of greenhouse gases, such as carbon dioxide emissions from burning fossil fuels or from deforestation, which trap heat that would otherwise escape from Earth. This is a type of greenhouse effect.
Earth's climate is mostly influenced by the first 6 miles or so of the atmosphere which contains most of the matter making up the atmosphere. This is really a very thin layer if you think about it. In the book The End of Nature, author Bill McKibbin tells of walking three miles to from his cabin in the Adirondack's to buy food. Afterwards, he realized that on this short journey he had traveled a distance equal to that of the layer of the atmosphere where almost all the action of our climate is contained. In fact, if you were to view Earth from space, the principle part of the atmosphere would only be about as thick as the skin on an onion! Realizing this makes it more plausible to suppose that human beings can change the climate. A look at the amount of greenhouse gases we are spewing into the atmosphere (see below), makes it even more plausible.
The most significant greenhouse gas is actually water vapor, not something produced directly by humankind in significant amounts. However, even slight increases in atmospheric levels of carbon dioxide (CO2) can cause a substantial increase in temperature.
Why is this? There are two reasons: First, although the concentrations of these gases are not nearly as large as that of oxygen and nitrogen (the main constituents of the atmosphere), neither oxygen or nitrogen are greenhouse gases. This is because neither has more than two atoms per molecule (i.e. their molecular forms are O2 and N2, respectively), and so they lack the internal vibrational modes that molecules with more than two atoms have. Both water and CO2, for example, have these "internal vibrational modes", and these vibrational modes can absorb and reradiate infrared radiation, which causes the greenhouse effect.
Secondly, CO2 tends to remain in the atmosphere for a very long time (time scales in the hundreds of years). Water vapor, on the other hand, can easily condense or evaporate, depending on local conditions. Water vapor levels therefore tend to adjust quickly to the prevailing conditions, such that the energy flows from the Sun and re-radiation from the Earth achieve a balance. CO2 tends to remain fairly constant and therefore behave as a controlling factor, rather than a reacting factor. More CO2 means that the balance occurs at higher temperatures and water vapor levels.
Human beings have increased the CO2 concentration in the atmosphere by about thirty percent, which is an extremely significant increase, even on inter-glacial timescales. It is believed that human beings are responsible for this because the increase is almost perfectly correlated with increases in fossil fuel combustion, and also due other evidence, such as changes in the ratios of different carbon isotopes in atmospheric CO2 that are consistent with "anthropogenic" (human caused) emissions. The simple fact is, that under "business as usual" conditions, we'll soon reach carbon dioxide concentrations that haven't been seen on Earth in the last 50 million years.
Combustion of Fossil Fuels, for electricity generation, transportation, and heating, and also the manufacture of cement, all result in the total worldwide emission of about 22 billion tons of carbon dioxide to the atmosphere each year. About a third of this comes from electricity generation, and another third from transportation, and a third from all other sources.
This enormous input of CO2 is causing the atmospheric levels of CO2 to rise dramatically. The following graph shows the CO2 levels over the past 160 thousand years (the upper curve, with units indicated on the right hand side of the graph). The current level, and projected increase over the next hundred years if we do not curb emissions, are also shown (the part of the curve which goes way up high, to the right of the current level, is the projected CO2 rise). The projected increase in CO2 is very startling and disturbing. Changes in the Earth's average surface temperature are also shown (the lower curve, with units on the left). Note that it parallels the CO2 level curve very well.
Yes! As everyone has heard from the media, recent years have consistently been the warmest in hundreds and possibly thousands of years. But that might be a temporary fluctuation, right? To see that it probably isn't, the next graph shows the average temperature in the Northern Hemisphere as determined from many sources, carefully combined, such as tree rings, corals, human records, etc.
These graphs show a very discernable warming trend, starting in about 1900. It might seem a bit surprising that warming started as early as 1900. How is this possible? The reason is that the increase in carbon dioxide actually began in 1800, following the deforestation of much of Northeastern American and other forested parts of the world. The sharp upswing in emissions during the industrial revolution further added to this, leading to a significantly increased carbon dioxide level even by 1900.
Thus, we see that Global Warming is not something far off in the future - in fact it predates almost every living human being today.
Computer models strongly suggest that this is the case. The following graphs show that 1) If only natural fluctuations are included in the models (such as the slight increase in solar output that occurred in the first half of the 20th century), then the large warming in the 20th century is not reproduced. 2) If only anthropogenic carbon emissions are included, then the large warming is reproduced, but some of the variations, such as the cooling period in the 1950s, is not reproduced (this cooling trend was thought to be caused by sulfur dioxide emissions from dirty power plants). 3) When both natural and anthropogenic emissions of all types are included, then the temperature evolution of the 20th century is well reproduced.
Yes. A recent study by the National Oceanic and Atmospheric Administration gives strong evidence that global warming was a major factor. Click here for more details.
Most of the scientific community, represented especially by the Intergovernmental Panel on Climate Change (IPCC - www.ipcc.ch), now believes that the global warming effect is real, and many corporations, even including Ford Motor Company, also acknowledge its likelihood.
In
1998, the Intergovernmental Panel on Climate Change (IPCC) was established by
the World Meteorological Organization (WMO) and the United Nations Environment
Programme (UNEP), in recognition of the threat that global warming presents to
the world.
The
IPCC is open to all members of the UNEP and WMO and consists of several thousand
of the most authoritative scientists in the world on climate change. The role of
the IPCC is to assess the scientific, technical and socio-economic information
relevant for the understanding of the risk of human-induced climate change. It
does not carry out new research nor does it monitor climate related data. It
bases its assessment mainly on published and peer reviewed scientific technical
literature.
The
IPCC has completed two assessment reports, developed methodology guidelines for
national greenhouse gas inventories, special reports and technical papers.
Results of the first assessment (1990--1994): confirmed scientific
basis for global warming but concluded that ``nothing to be said for certain
yet''. The
second assessment (1995), concluded that `` ...the balance suggests a discernable human influence on
global climate'', and concluded that, as predicted by climate models, global
temperature will likely rise by about 1-3.5
Due
to these assessments,
debate has now shifted away from whether or not global warming is going to occur
to, instead, how much, how soon, and with what impacts.
Many of the following "harbingers" and "fingerprints" are now well under way:
In reality, we will need to work on all fronts - 10% here, 5% here, etc, and work to phase in new technologies, such as hydrogen technology, as quickly as possible. To satisfy the Kyoto protocol, developed countries would be required to cut back their emissions by a total of 5.2 % between 2008 and 2012 from 1990 levels. Specifically, the US would have to reduce its presently projected 2010 annual emissions by 400 million tons of CO2 . One should keep in mind though, that even Kyoto would only go a little ways towards solving the problem. In reality, much more needs to be done.
The most promising sector for near term reductions is widely thought to
be coal-fired electricity. Wind power, for example, can make substantial cuts in
these emissions in the near term, as can energy efficiency, and also the
increased use of high efficiency natural gas generation.
The potential impact of efficiency should not be underestimated: A 1991 report to Congress by the U.S. National Academy of Sciences, Policy Implications of Greenhouse Warming, found that the U.S. could reduce current emissions by 50 percent at zero cost to the economy as a result of full use of cost-effective efficiency improvements.
Here is a useful list of facts and ideas:
Many government agencies around the world are very interested in maintaining fossil fuel use, especially coal. It should be noted that US energy use, which is enormous, is increasing, not decreasing. Furthermore, we are not going to run out of coal in the near term (oil may begin to run low sometime after 2010). Methods for reducing carbon emission levels while still burning coal are now investigation by government and industry, as we now discuss.
We believe that a major increase in renewable energy use should be achieved to help offset global warming. While there are some US government programs aimed in this direction, there is simply not enough money being spent yet to achieve this goal in a timely manner. A primary goal of many new programs is not to increase renewables, but rather, is to find ways to capture the extra CO2 from electricity generation plants and "sequester" it in the ground, the ocean, or by having plants and soil organisms absorb more of it from the air.
One of the Carbon sequestration approaches under investigation is the possibility of depositing CO2 extracted from emission streams in large pools on the Ocean bottom. It is possible that such pools will not be stable, and may either erupt to the surface, or diffuse into the ocean and alter the oceans pH.
Another scheme under investigation is the idea of stimulating phytoplankton growth on the ocean surface by dusting the surface with iron (the limiting nutrient). This will cause an increased uptake of carbon by the plankton, part of which will find its way to the ocean bottom. Fishing companies are considering using this to increase fish harvests while simultaneously getting credit for carbon sequestration. Serious ecological disruptions could occur, however, especially if this approach is conducted on a sufficiently large scale.
Another idea is to stimulate Earth's terrestrial ecosystems to take up more carbon dioxide. While the impacts here are more difficult to ascertain, an important point to note is that these systems are not thought to be able to completely absorb all the extra CO2 . At best, they may be sufficient to help the US stabilize carbon emission rates for a few decades, but even if this is achieved, stabilization of rates are not likely to return the Earth to pre-industrial carbon levels. Worse, biological feedbacks to global warming, such as forest fires, drying soils, rotting permafrost, etc, may actually greatly accelerate carbon emissions, i.e. we may experience massive carbon de-sequestration.
Another major approach under consideration is to pump CO2 into old oil and gas wells. While seemingly attractive, it must be kept in mind that for this to be truly effective, it would have to be done on a world wide scale, include many sources of CO2 , including many sources which are presently small and widely distributed (such as car emissions, and not just coal plant emissions). All of this CO2 would need to be captured, transported, injected into old wells, and then the wells would need to be sealed and monitored. It is not clear that this would be affordable at all, and that there would be adequate capacity or assurance that CO2 would not leak out in massive quantities.
In the worst case scenario, carbon sequestration efforts may simply fail, but also end up being a political tool that is used to seriously delay a transition to renewable energy sources, and also possibly create many new environmental problems problems while prolonging old ones.
In the best case scenario, given the truly enormous amount of CO2 we are presently emitting, some sequestration approaches may serve as a useful bridge to curbing emissions while the transition to renewables is being made.
IPCC site: http://www.ipcc.ch
US Global Change Research Program: www.usgcrp.gov
Weathervane: an
online forum designed to provide the news
media, legislators, opinion leaders, and the interested public with
analysis and commentary on U.S. and global policy initiatives related to climate change. http://www.weathervane.rff.org/
The global warming primer and discussion at website of the Institute of Geophysics and Planetary Physics at Los Alamos National Laboratory: http://www.igpp.lanl.gov
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