Climate Change
Earth's Surface Temperatures Are RisingClimate change in the form of global warming is considered by many scientists to be the most serious threat facing the world today.
The term 'global warming' refers to the accelerated warming of the Earth's atmosphere caused by the buildup of one or more 'greenhouse gases' (primarily carbon dioxide, methane, and nitrous oxide) due in large part to human activities. Human factors that contribute to global warming include the combustion of fossil fuels, the burning of forests, and methane emissions from livestock. In Australia, continental average temperatures have risen 0.7°C between 1910 and 1999, and are expected to rise by 1.0 to 6.0°C by 2070. In comparison, global average air temperature is projected to rise by 2.5°C (with a range of uncertainty of 1.5 to 4.5 °C) by the year 2100. To put a 2.5°C temperature change into perspective, the temperature difference between a glacial and an interglacial period (i.e. an intervening warm period between glacials) is about 5-6°C.
According to the National Academy of Sciences, the Earth's surface temperature has risen by about 1 degree Fahrenheit in the past century, with accelerated warming during the past two decades. There is new and stronger evidence that most of the warming over the last 50 years is attributable to human activities that have altered the chemical composition of the atmosphere through the buildup of greenhouse gases - primarily carbon dioxide, methane, and nitrous oxide. The heat-trapping property of these gases is undisputed, although uncertainties exist about exactly how Earth's climate responds to them. In order to decelerate this dangerous trend, we need to work on creating and using environmental recycling systems that will restore the delicate balance between nature and human activities.
Our Changing Atmosphere
The temperature of the atmosphere near the Earth's surface is warmed through a natural process called the greenhouse effect. Visible, shortwave light comes from the sun to the earth, passing unimpeded through a blanket of thermal, or greenhouse, gases composed largely of water vapor, carbon dioxide, methane, nitrous oxide, and ozone. Infrared radiation reflects off the planet's surface toward space but does not easily pass through the thermal blanket. Some of it is trapped and reflected downward, keeping the planet at an average temperature, suitable to life, of about 60°F (16°C).
Since the dawn of the Industrial Revolution, atmospheric concentrations of carbon dioxide have increased by 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 atmosphere. And while sulfate aerosols, a common air pollutant, do cool the atmosphere by reflecting light back into space, they 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 in the atmosphere. Plant respiration and the decomposition of organic matter release more than 10 times the CO2 released by human activities; but these releases have generally been balanced, during the centuries leading up to the industrial revolution, by the absorption of carbon dioxide by terrestrial vegetation and the oceans.
What has changed in the last few hundred years is the release of additional carbon dioxide by human activities. Fossil fuels burned to run cars and trucks, heat homes and businesses, and power factories are responsible for about 98% of U.S. carbon dioxide emissions, 24% of methane emissions, and 18% of nitrous oxide emissions. Increased agriculture, deforestation, landfills, industrial production, and mining also contribute a significant share of emissions. In 1997, the United States emitted about one fifth of total global greenhouse gases. For many years these emissions and their effects on the environment were ignored due to lack of understanding and commitment towards environmental recycling solutions. As knowledge and concern for the environment increase, more emphasis is being placed on developing technologies for environmental recycling solutions by government bodies, companies and individuals with an interest in viable self sustentation.
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.
For detailed graphs and figures on global warming please visit:
http://www.ipcc.ch
http://www.grida.no
http://www.pewclimate.org
http://en.wikipedia.org/wiki/Global_warming
| The concentration of carbon dioxide in Earth's atmosphere is nearing 390 parts per million by volume (ppm) and rising. Scientists indicate that levels around 450 ppm could create dramatic consequences for the climate and the environment. |
