Green House Effect and Climate Change

The sun emits ultraviolet (UV) radiation which hits the earth.These rays of light hit the earth and reflect back towards space in the form of UV as well as Infrared (IR) radiation.

gases in the atmosphere pick up some of the heat from the IR rays and disperse them back into  the earth’s atmosphere keeping the earth warm enough to sustain life

•Is a natural process that permits the Earth to retain some of the heat from the sun.

•Gases in the atmosphere (water vapor, carbon dioxide, nitrous oxide, and methane) trap energy from the sun.

•Without these gases, heat would escape back into space and Earth’s average  temperature would be about -18 °C .

•Because of how they warm our world, these gases are referred to as greenhouse gases.

•A portion of the energy (26%) is reflected or scattered 

back to space.

•About 19% of the energy available is absorbed by clouds, 

gases like ozone.

•The remaining 55% of the energy passing through the 

Earth's atmosphere, 4% is reflected from the surface back to space.

•On average, about 51% of the Sun's radiation reaches the 

surface. 

•This energy is then used in a number of processes, 

including the heating of the ground surface; the melting 

of ice and snow and the evaporation of water; and plant  

photosynthesis.

 

CO2 comes from a variety of sources. For example, plants take up carbon dioxide in the air to make wood, stems, and leaves, and then release it back into the air when the leaves fall or the plants die. The concern today is that fossil fuel use is putting huge amounts of CO2 in the atmosphere at a rate faster than the climate system can adapt to

         In addition, the warming resulting from CO2 and other greenhouse gases also has the effect of increasing evaporation.  This adds water vapor to the atmosphere as well. Water vapor is the most important gas in the natural greenhouse effect, contributing 60% of the effect to carbon dioxide’s 26%. And in fact, satellites have detected an increase in atmospheric moisture over the oceans at a rate of 4% per degree F of warming (7% per degree C) since 1988. This additional water vapor amplifies the warming effect.  

     Certainly, past temperatures past have been higher (and lower) than today, and

       CO2 concentrations have also varied. Large global swings were probably caused by such things as changes in Earth’s orbit, which changed the distribution of sunlight over the planet. When this caused warming, more CO2 and other greenhouse gases were released, producing additional warming. 

         But today, the CO2 released by human activities is far above amounts in the previous 800,000 years. This CO2 is triggering the increase in temperatures we’ve seen.

         Earth is getting warmer by virtually every measure we know, and the temperature has been well above normal for more than 25 years. Although increases of 1.0-1.6°F (0.6-0.9°C) over the last century or so may not sound very threatening, remember that’s a global average. The warming is stronger over land than over oceans and in the higher latitudes than in the tropics. 

         Snow and ice reflect the sun’s energy back to space. Without this white cover, more water can evaporate into the atmosphere where it acts as a greenhouse gas, and the ground absorbs more heat. Snow and ice are melting at rates unseen for thousands of years. In Glacier National Park, for example, there were 150 glaciers in 1850. Today, there are 26.  

          Sea ice is dwindling too, especially in the Northern Hemisphere. Satellites have seen average Arctic sea ice shrink by 2.7% per decade from 1978 to 2006, with faster melting in summer. 

         More water vapor held by a warmer atmosphere also leads to heavier rains and more snowfall.  Intense precipitation over the U.S. has increased 20% over the last century.

         But as storm tracks shift, it can also mean some areas get drier. A 2004 study by the National Center for Atmospheric Research found that the percentage of Earth’s land experiencing serious drought had more than doubled since the 1970s.

        Increased warmth has also affected living things. For example, the Japanese keep very detailed records on the blossoming of their Tokyo cherry trees, so they know they are blooming 5 days earlier on average than they were 50 years ago. 

     Also mosquitoes, birds, and insects are moving north in the Northern Hemisphere. 

        

         Global average temperatures are expected to increase by about 2-13°F (1-7°C) by the end of the century. That may not sound like a lot, so what’s the big deal? The problem is that small changes in global average temperature can lead to really large changes in the environment. Let’s look at some of the expected changes.