Our sun can warm up the Earth. But if the sun’s rays are reflected back into space, the heat is lost. Thus Mars, with practically no gases in its atmosphere, stays below freezing; Venus, with 300 times the carbon dioxide as Earth, is hot enough to melt nickel; but Earth has maintained life-sustaining temperatures due to the right level of greenhouse gases in its atmosphere. A layer of greenhouse gases – primarily water vapor, and including much smaller amounts of carbon dioxide (CO2), methane and nitrous oxide – acts as a thermal blanket for the Earth, absorbing solar heat and warming the air to a life-supporting average of 59 degrees Fahrenheit.
Most climate scientists agree the current global warming trend is due mainly to human expansion of the greenhouse effect. Ice cores drawn from Greenland, Antarctica and mountain glaciers show that the CO2 levels were around 250-280 parts per million (ppm), as measured from ice cores 800,000 years old, prior to the Industrial Revolution in the late 1800s, when large amounts of greenhouse gases began to be released by the burning of fossil fuels – coal, gas and oil. In March the global average for CO2 reached 400.83 ppm, a new high for an entire month since such measurements began in the late 1950s. According to the National Oceanic and Atmospheric Administration, CO2 is responsible for 63 percent of the warming attributable to all greenhouse gases.
Man’s increasing reliance on burning fossil fuels has caused increasing amounts of CO2 in our atmosphere. To a lesser extent, the clearing of land for agriculture, industry, and other human activities, have increased concentrations of greenhouse gases. Since 1880 the average global temperature has increased by 1.4 degrees Fahrenheit. The oceans have absorbed much of this increased heat, warming the top 2,300 feet of ocean by 0.302 degrees Fahrenheit since 1969. The melting of ice sheets from oceans and glaciers in various parts of the world has caused the global sea level to rise 6.7 inches, with the last decade’s rate nearly double that of the last century. The disappearance of snow covers and glaciers around the world’s mountains will diminish these sources as possible future supplies of fresh water.
The absorption of CO2 in the upper layer of ocean waters has increased the surface acidity by about 30 percent since 1850. A more acidic ocean is affecting plankton (which provide half of the oxygen we breathe) and many marine organisms, resulting in a decrease of six percent over the last 30 years in the ocean’s capacity to provide oxygen and support the food chains. In addition, warmer oceans are less able to store CO2 – emitting more CO2 back into the atmosphere where it causes further warming. Local climates around the world still go through their different weather cycles, but with some unexpected shifts. In recent decades droughts, wild forest fires, floods and violent storms occur more frequently.
Next month: Choose a more efficient lifestyle to decrease global warming.