Green house gases
The greenhouse effect is the process by which absorption and emission of infrared radiation by gases in a planet's atmosphere warm its lower atmosphere and surface. It was proposed by Joseph Fourier in 1824, discovered in 1860 by John Tyndall, was first investigated quantitatively by Svante Arrhenius in 1896, and was developed in the 1930s through 1960s by Guy Stewart Callendar.
The primary components of Earth’s atmosphere, N2 and O2 do not have absorption in the IR wavelength range, therefore, do not have a significant role in setting the surface temperature of the planet.
Greenhouse gas is efficient in absorbing IR light. The most important greenhouse gases are:
· H2O – Water vapor.
· Cabon dioxide – Carbon Dioxide.
· CH4 – Methane.
The most abundant greenhouse gas in Earth’s atmosphere is water vapor. Most of the greenhouse heating of Earth’s atmosphere is due to Water vapor absorption of IR radiation emitted by Earth, and then transferring the energy to the surrounding air molecule.
Carbon Dioxide
Cabon dioxide is a colorless gas:
• Condenses into solid form (dry ice) at -78°C in atmospheric pressure.
• Condenses into liquid at -57°C at pressure above 5.1 atmospheric pressure.
Atmospheric Cabon dioxide is derived from the sources for example:
• Volcanic out gassing
• burning of organic matter
• Respiration of living organisms
Cabon dioxide can be stored in the go under
• Highly soluble in water: forms H2CO3
• Dissolved Cabon dioxide in water can interact with silicate minerals to form carbonated minerals.
Human activity since the Industrial Revolution has increased the amount of greenhouse gases in the atmosphere, leading to increased radiative forcing from Cabon dioxide, methane, tropospheric ozone, CFCs and NO. According to work published in 2007, the concentrations of Cabon dioxide and methane have increased by 36% and 148% respectively since 1750. These levels are much higher than at any time during the last 800,000 years, the period for which reliable data has been extracted from ice cores. Less direct geological evidence indicates that Cabon dioxide values higher than this were last seen about 20 million years ago. Fossel burning has produced about three-quarters of the increase in Cabon dioxide from human activity over the past 20 years. The rest of this increase is caused mostly by changes in land-use, particularly deforestration. Estimates of global Cabon dioxide emissions in 2011 from fossil fuel combustion, including cement production and gas flaring, were 34.8 billion tones, an increase of 54% above emissions in 1990. Coal burning was responsible for 43% of the total emissions, oil 34%, gas 18%, cement 4.9% and gas flaring 0.7% In May 2013, it was reported that readings for Cabon dioxide taken at the world's primary benchmark site in Mauna Loa surpassed 400 ppm. According to professor Brian Hoskins, this is likely the first time Caron dioxide levels have been this high for about 4.5 million years.
Effect on Human Health
November 1, 2011 Critics who doubt dire predictions about global warming question how much difference, say, a 2-degree temperature increase could mean to the planet.
According to Aaron Bernstein, quite a bit. Bernstein, a doctor at Children’s Hospital, instructor in pediatrics at Harvard Medical School, and Acting Associate Director of the medical school’s Center for Health and the Global Environment, was the first speaker in this year’s Environmental Health Colloquium Series, held on October 20, 2011 and sponsored by the Harvard School of Public Health’sDepartment of Environmental Health. An expert in how climate change and biodiversity loss can affect human health, Bernstein, MPH ’09, said that even a small global temperature increase could lead to troubling consequences, like rising sea levels, population displacement, disruption to the food supply, flooding, and an increase in infectious diseases.
While some don’t believe that greenhouse gases caused by humans are the main culprit behind global warming, Bernstein showed graphs indicating otherwise. The data, he explained, show pronounced increases in greenhouse gas levels in the United States during the Industrial Revolution of the late 1800s as well in the 1950s, when there was a postwar manufacturing boom.
Three consequences of climate change rising sea levels, rising temperatures, and increased precipitation stand to have the greatest impact on human health, Bernstein said. With rising sea levels, salt water can seep into into groundwater tables and taint the drinking water supply, and can also displace populations from low-lying areas. “And displaced populations have notoriously poor health statistics,” he said.
Heat waves another consequence of global warming can lead to thousands of heat-related deaths. Beyond that, there can be other troubling effects: decreases in crop yields, droughts, and dry conditions ripe for wildfires. Wildfires, in turn, lead to deforestation. Since trees absorb much of the excess carbon dioxide in the atmosphere, fewer trees mean higher levels of greenhouse gases in the atmosphere thus perpetuating the cycle in which warmer temperatures wreak atmospheric havoc.
Global warming can also cause abnormally heavy rains. A warmer atmosphere holds more moisture than a cooler one, Bernstein explained, but when it reaches capacity, the rain can be overwhelming. As an example, he cited the unprecedented spring flooding in the Midwest, which prompted the Army Corps of Engineers to intentionally breach the Birds Point levee in southeastern Missouri. The move saved the town of Cairo, Illinois, but it swamped 130,000 acres of Missouri farmland and 100 homes.
Key facts
· Climate change affects the social and environmental determinants of health clean air, safe drinking water, sufficient food and secure shelter.
· Global warming that has occurred since the 1970s caused over 140 000 excess deaths annually by the year 2004.
· The direct damage costs to health (i.e. excluding costs in health-determining sectors such as agriculture and water and sanitation), is estimated to be between US$ 2-4 billion/year by 2030.
· Many of the major killers such as diarrhoeal diseases, malnutrition, malaria and dengue are highly climate-sensitive and are expected to worsen as the climate changes.
· Areas with weak health infrastructure mostly in developing countries – will be the least able to cope without assistance to prepare and respond.
· Reducing emissions of greenhouse gases through better transport, food and energy-use choices can result in improved health.
Climate change
Over the last 50 years, human activities – particularly the burning of fossil fuels – have released sufficient quantities of carbon dioxide and other greenhouse gases to trap additional heat in the lower atmosphere and affect the global climate.
· In the last 100 years, the world has warmed by approximately 0.75 digree centigrade. Over the last 25 years, the rate of global warming has accelerated, at over 0.18 digree centigrade per decade1.
· Sea levels are rising, glaciers are melting and precipitation patterns are changing. Extreme weather events are becoming more intense and frequent.
What is the impact of climate change on health?
Although global warming may bring some localized benefits, such as fewer winter deaths in temperate climates and increased food production in certain areas, the overall health effects of a changing climate are likely to be overwhelmingly negative. Climate change affects social and environmental determinants of health clean air, safe drinking water, sufficient food and secure shelter.
