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The Greenhouse Effect and the Global Warming

M.De Vita, A.Pafundi, N.Pecoraro (*) I.Ionita (**) - Linguistic Mediator: R.Triggiano (*)
(*) Istituto Alfano I - (**) University of Galati

| Introduction | Greenhouse Gases | Atmosphere | Climate | Kyoto Protocol | Links |

An Introduction

According to the United States National Academy of Sciences, the Earth's surface temperature has risen by about 0.6°C in the past century, with accelerated warming during the past two decades. The latest test has shown that in the last 15 years of the XX century we had the hottest 10 years; 1998 was the hottest one. Besides, it is supposed that the average global surface temperature can rise of 0.6 – 2.5°C in the following 15 years and of 1.4 – 5.8°C in the current century. Energy from the sun drives the earth’s weather and climate, and heats the earth’s surface; in turn, the earth radiates energy back into space. Atmospheric greenhouse gases (water vapor, carbon dioxide, and other gases) trap some of the outgoing energy, retaining heat somewhat like the glass panels of a greenhouse. Without this natural “greenhouse effect,” temperatures would be much lower than they are now, and life as known today would not be possible. Instead, thanks to greenhouse gases, the earth’s average temperature is a more hospitable 15.6°C. However, problems may arise when the atmospheric concentration of greenhouse gases increases.

The Greenhouse Effect

The Greenhouse Effect

http://yosemite.epa.gov/OAR/globalwarming.nsf/content/Climate.html

What Are Greenhouse Gases?

Some greenhouse gases occur naturally in the atmosphere, while others result from human activities. Naturally occurring greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Certain human activities, however, add to the levels of most of these naturally occurring gases: Carbon dioxide is released to the atmosphere when solid waste, fossil fuels (oil, natural gas, and coal), and wood and wood products are burned. Methane is emitted during the production and transport of coal, natural gas, and oil. Methane emissions also result from the decomposition of organic wastes in municipal solid waste landfills, and the raising of livestock. Nitrous oxide is emitted during agricultural and industrial activities, as well as during combustion of solid waste and fossil fuels. Very powerful greenhouse gases that are not naturally occurring include hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6), which are generated in a variety of industrial processes. Each greenhouse gas differs in its ability to absorb heat in the atmosphere. HFCs and PFCs are the most heat-absorbent. Methane traps over 21 times more heat per molecule than carbon dioxide, and nitrous oxide absorbs 270 times more heat per molecule than carbon dioxide. Often, estimates of greenhouse gas emissions are presented in units of millions of metric tons of carbon equivalents (MMTCE), which weights each gas by its GWP value, or Global Warming Potential.

Our Changing Atmosphere

Since the beginning of the industrial revolution, atmospheric concentrations of carbon dioxide have increased nearly 30%, methane concentrations have more than doubled, and nitrous oxide concentrations have risen by about 15%. These increases have enhanced the heat-trapping capability of the earth’s atmosphere. Sulfate aerosols, a common air pollutant, cool the atmosphere by reflecting light back into space; however, sulfates are short-lived in the atmosphere and vary regionally. Why are greenhouse gas concentrations increasing? Scientists generally believe that the combustion of fossil fuels and other human activities are the primary reason for the increased concentration of carbon dioxide. The photosynthesis and the biomass release CO2 in the atmosphere 10 times more than the emission released by the human activities, but these releases have generally been in balance during the centuries leading up to the industrial revolution with carbon dioxide absorbed by terrestrial vegetation and the oceans. What has changed in the last few hundred years is the additional release of carbon dioxide by human activities. In the most developed countries the fossil combustible used for cars, for the central heating in the buildings and for supplying electric power station is responsible by 95% for the emission of carbon dioxide, the methane is responsible by 20% and nitrous oxide by 15%. Increased agriculture, deforestation, landfills, industrial production, and mining also contribute a significant share of emissions. Estimating future emissions is difficult, because it depends on demographic, economic, technological, policy, and institutional developments. Several emissions scenarios have been developed based on differing projections of these underlying factors. For example, by 2100, in the absence of emissions control policies, carbon dioxide concentrations are projected to be 30-150% higher than today’s levels.

The Greenhouse Effect

A graph of Dr. Keeling’s now famous curve of increasing CO2 concentration.
http://calspace.ucsd.edu/virtualmuseum/climatechange2/08_1.shtml

 

Changing Climate

Global mean surface temperatures have increased 1°C since the late 19th century. The 20th century's 10 warmest years all occurred in the last 15 years of the century. Of these, 1998 was the warmest year on record. The snow cover in the Northern Hemisphere and floating ice in the Arctic Ocean have decreased. Globally, sea level has risen 4-8 inches over the past century. Worldwide precipitation over land has increased by about one percent. The frequency of extreme rainfall events has increased throughout much of the United States. Increasing concentrations of greenhouse gases are likely to accelerate the rate of climate change. Scientists expect that the average global surface temperature could raise 0.6-2.5 ° C in the next fifty years and 1.4-5.8 ° C in the next century, with significant regional variation. Evaporation will increase as the climate warms, which will increase average global precipitation. Soil moisture is likely to decline in many regions, and intense rainstorms are likely to become more frequent. Sea level is likely to rise two feet along most of the U.S. coast.

The Greenhouse Effect

A time series graph showing the combined global land and marine surface temperature record from 1856 to 2001. The temperature is plotted as the difference (called an “anomaly”) from the long-term average (a value calculated from the years 1961-1990).
http://calspace.ucsd.edu/virtualmuseum/climatechange2/08_1.shtml

 

The Kyoto Protocol

Kyoto Protocol is an international agreement subscribed by 84 countries in 1997; it deals with the possible greenhouse gases reduction. The target for the industrialized countries is the reduction of 5% (6.5 for Italy) within 2012, compared to their emission level of 1990. as there have been a remarkable increase of emission, the 5% reduction will be a very important result (the industrialized countries should reduce their emissions and not increase them) This agreement concerns six greenhouse gases: carbon dioxide, methane, nitrogen protoxide, perfluorocarbons, hydro fluorocarbons and sulphate hexafluoride and the limit of their emissions in 39 countries (among them: USA, European Union, Russia, Japan, Canada, Poland, Bulgaria and other east European countries, Switzerland and Norway. HFCs are not mentioned in Kyoto Protocol because their limit was already fixed in the previous Montreal Protocol 1991. In the last Montreal conference (from 28 November to 9 December 2005) was discussed how to take forward the Kyoto protocol on cutting carbon emissions to combat climate change. The Kyoto Protocol, committing 36 of the world's most developed nations to legally-binding emission targets, came into force in February last year. A total of 140 countries have ratified the Kyoto Convention, which itself grew out of the 1992 Rio Earth Summit, a watershed United Nations meeting. The industrialised nations that signed up to the protocol committed themselves to a combined reduction in emissions to 5% below 1990 levels by the period 2008-12, although each country is set an individual target. Japan, for example, will reduce its emissions by 5%, the EU by 8% and the UK government has declared its intention to cut greenhouse gasses by 10% by 2010. The independent International Climate Change Taskforce, co-chaired by former Labour minister Stephen Byers, has suggested fixing maximum global emissions at a level which will "only" raise average temperatures by two degrees this century (which many environmentalists see as now inevitable) and working back from there to deduce carbon cuts. It also calls on the formation of a "G8 plus" group, including India and China, to focus on climate change, and 25% of all energy provision to come from renewable by 2025. The UK has already committed to 20% by 2020.

Links

http://yosemite.epa.gov/OAR/globalwarming.nsf/content/Climate.html
http://zebu.uoregon.edu/1998/es202/l13.html
http://www.solcomhouse.com/globalwarming.htm
http://www.ran.org/info_center/factsheets/04a.html
http://unfccc.int/resource/docs/convkp/kpeng.html
http://www.eu.int/comm/environment/climat/kyoto.htm
http://calspace.ucsd.edu/virtualmuseum/climatechange2/08_1.shtml
http://cdiac.esd.ornl.gov/trends/co2/contents.htm

www.nonsoloaria.com

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