Embed Size (px)
Transcript of Global Warming
A Synthesis of Ideas Related to the Global Warming Controversy Edited by: Paul Jacob February 15th 2007
What is Global Warming? Definition: Global warming is the observed increase in the average temperature of the earth's atmosphere and oceans in recent decades and its projected continuation into the future.i The earths average near-surface atmospheric temperature rose 0.6 0.2 C (1.1 0.4 F) in the 20th Century.ii The prevailing scientific opinion on climate change is that most of the warming observed over the last 50 years is attributable to human activities.iii That being said, without greenhouse gases, the earth would be 33 C colder than it currently is,iv which is undesirable to all concerned climate change activists and global warming nay-sayers alike. Though much of the global warming effect is created by the presence of water vapor, humans also play a part. The increased amounts of carbon dioxide (CO2), methane (CH4), and Nitrous Oxide (N2O), are the primary causes of the human-induced component of warming.v They are released by the burning of fossil fuels, land clearing, agriculture, etc. and lead to an increase in the greenhouse effect.vi The percentage breakdown of each major human-induced greenhouse gas for the year 2000 is shown in the chart below:vii
On the other hand, it is important to keep in mind that there are fundamentally nonhuman aspects to global warming, including but not limited to: water vapor, which may account for some 70-95% of global warming related causes, or even more; but that will be discussed in more depth later in this report. If Global Warming is True, Whats the Downside? An increase in global temperatures can in turn cause other changes, including a rising sea level and changes in the amount and pattern of precipitation.viii These changes may increase the frequency and intensity of extreme weather events, such as floods, droughts, heat waves, hurricanes, and tornados.ix Other consequences include higher or lower agricultural yields, glacial retreat, reduced summer streamflows, species extinctions, and increases in the ranges of disease vectors.x Warming is expected to affect the number and magnitude of these events: however, it is difficult to connect particular events to global warming.xi Although most studies focus on the period up to 2100, warming (and sea level rise due to thermal expansion) is expected to continue past then, since CO2 has a long average atmospheric lifetime.xii
Remaining scientific uncertainties include the exact degree of climate change expected in the future, and especially how changes will vary from region to region across the globe.xiii A hotly contested political and public debate has yet to be resolved regarding whether
anything should be done, and what could be cost-effectively done to reduce or reverse future warming, or to deal with the expected consequences.xiv
The Bhutan-Himalaya Glaciers (aerial photo shows forming glacial lakes) What is the Greenhouse Effect? Definition: The warming of the atmosphere by the trapping of longwave radiation being radiated to space.xv The term 'greenhouse effect' originally came from the greenhouses used for gardening, but it is a misnomer since greenhouses operate differently.xvi A greenhouse is built of glass; it heats up primarily because the sun warms the ground inside it, which warms the air near the ground, and this air is prevented from rising and flowing away.xvii The warming inside a greenhouse thus occurs by suppressing convection and turbulent mixing.xviii This can be demonstrated by opening a small window near the roof of a greenhouse: the temperature will drop considerably.xix It has also been demonstrated experimentally: a "greenhouse" built of rock salt (which is transparent to IR) heats up just as one built of glass does.xx Greenhouses thus work primarily by preventing convection; the atmospheric greenhouse effect however reduces radiation loss, not convection.xxi It is quite common, however, to find sources that make the "greenhouse" analogy.xxii Although the primary mechanism for warming greenhouses is the prevention of mixing with the free atmosphere, the radiative properties of the glazing can still be important to commercial growers.xxiii With the modern development of new plastic surfaces and glazings for greenhouses, this has permitted construction of greenhouses which selectively control radiation transmittance in order to better control the growing environment.xxiv Concerning the greenhouse effect, the earth naturally absorbs and reflects incoming solar radiation and emits longer wavelength terrestrial (thermal) radiation back into space.xxv
On average, the absorbed solar radiation is balanced by the outgoing terrestrial radiation emitted to space.xxvi A portion of this terrestrial radiation, though, is itself absorbed by gases in the atmosphere.xxvii The energy from this absorbed terrestrial radiation warms the earths surface and atmosphere, creating what is known as the natural greenhouse effect. xxviii Without the natural heat-trapping properties of these atmospheric gases, the average surface temperature of the earth would be about 33 C lower.xxix The following Diagram shows how the greenhouse effect works.
Greenhouse Gases Greenhouse gases (GHGs) are gaseous components of the atmosphere that contribute to the greenhouse effect.xxx Some greenhouse gases occur naturally in the atmosphere, while others result from human activities.xxxi Naturally occurring greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, and ozone.xxxii Certain human activities, however, add to the levels of most of these naturally occurring gases.xxxiii The major natural greenhouse gases are water vapor, which causes about 36-70% of the greenhouse effect on earth (not including clouds); carbon dioxide, which causes 9-26%; methane, which causes 4-9%, and ozone, which causes 3-7%.xxxiv It is not possible to state that a certain gas causes a certain percentage of the greenhouse effect, because the influences of the various gases are not additive (the higher ends of the range quoted are 5
for the gas alone; the lower ends, for the gas counting overlaps).xxxv Other greenhouse gases include, but are not limited to: nitrous oxide, sulfur hexafluoride, hydrofluorocarbons, perfluorocarbons, and chlorofuorocarbons (see IPCC list of greenhouse gases).xxxvi The major atmospheric constituents (nitrogen, N2 and oxygen, O2) are not greenhouse gases.xxxvii This is because homonuclear molecules such as N2 and O2 neither absorb nor emit infrared radiation as there is no net change to the dipole moment of these molecules.xxxviii Two Differing Points of View: CO2 as the most important Greenhouse Gas vs. Water Vapor as the most important Greenhouse Gas CO2 is the Most Important Greenhouse Gas Some scientific sources and environmental agencies choose to neglect the effects of water vapor as the most prominent greenhouse gas, and instead focus on CO2 as the predominant greenhouse gas. For instance, The Kyoto Protocol the amendment to the UN Global climate treaty fails to mention water vapor as a concern and instead focuses on CO2 as the leading emission in the battle against global warming. This seems odd since the protocols objective is to eliminate excess degrees of greenhouse gases in the atmosphere in order to quell the Global Warming Phenomenon. From the United Nations Framework Convention on Climate Change website, we can find the following purpose statement for the Kyoto Protocol ratification to the United Nations Global Climate Treaty: The 1997 Kyoto Protocol shares the Conventions objective, principles and institutions, but significantly strengthens the Convention by committing Annex I Parties to individual, legally-binding targets to limit or reduce their greenhouse gas emissions. Only Parties to the Convention that have also become Parties to the Protocol (i.e. by ratifying, accepting, approving, or acceding to it) will be bound by the Protocols commitments. 168 countries and one regional economic integration organization (the EEC) have ratified the Protocol to date. Of these, 35countries and the EEC are required to reduce greenhouse gas emissions below levels specified for each of them in the treaty. The individual targets for Annex I Parties are listed in the Kyoto Protocols Annex B. These add up to a total cut in greenhouse-gas emissions of at least 5% from 1990 levels in the commitment period 2008-2012.xxxix Now, to be fair, the reason why the UN might disregard the effects of water vapor is that this greenhouse gas is not man-made. Moreover, some climate analysts say that the greenhouse gas emissions which are man-made only spur the increase in water vapor; and that in the end, these greenhouse gases (CO2, CH4, Nitrous Oxide, etc.) are responsible for the water vapor increase. This is called Water Vapour Feedback, and is claimed to be a scientific reason for avoiding anthropogenic (human induced) gases all the more. For example, Lonnie Thompson, a climatologist at Ohio State University who studies ice cores and glacier retreat, said, This research indicates that small changes in temperature,
driven by greenhouse gases, put more water vapor into the atmosphere, which drives up the temperature more.xl Furthermore, some scientists claim that water vapor balances itself out because it can reflect both shortwave and longwave radiation from the sun and earth respectively. This tendency to reflect from both directions would mean that water vapor both prevents and adds to the problem of Global Warming.
2. Water Vapor is the Most important Greenhouse Gas Other scientists have a different notion of the importance of water vapor in effecting the climate. They believe that the water vapor increases which we have experienced in the past century are the main cause of global warming,