The Changing Climate

The Changing Climate
1. ?Earth?s climate has always been changing; it is the rate of change that is of current concern to scientists.? With reference to Figure 1, and other evidence which you have come across, discuss the validity of this statement. Firstly, global climate change is defined as ?a change in the long-term weather patterns that characterize the regions of the world.? From Figure 1, we can see that the Earth?s climate has always been changing (at least temperature-wise), as evidenced by the large fluctuations in temperature as shown in the graph, starting from 150000 years ago. Figure 1 [image]As shown in the graph, the average global temperature dropped for around 15000 years, and then started to increase sharply for around 10000 years, after which it dropped at remained relatively constant, although it continued to fluctuate by around 1-2oC. The average temperature then dropped sharply around 80000 years ago, and then rose again, followed by another 35000 years or so of relative constant temperature.
After that, the temperature dropped steadily until around 15000 years ago, after which it began to rise sharply, with only a small decrease in the rate of increase in the past 2000 years. Hence, from figure 1 alone, we can see that the rate of change in the Earth?s global average temperature has been increasing over the past 15000 years, and even though the rate of change decreased somewhat during the past 5000 years or so, the worldwide average temperature is still on the rise. Therefore it is true that the rate of change could be potentially a concern to scientists. However, temperature is not the only climatic factor that is changing rapidly today. Concentrations of greenhouse gases in the atmosphere have increased sharply over the past two centuries, and this is in fact the cause of the increase in average global temperature, and more on this will be said in question 2. The current rate of change in the concentration of carbon dioxide in the atmosphere is something that has caused scientists to worry about, and this is illustrated in Figure 2. Figure 2 [image][image] Figure 3 As shown in the figure, the concentration of CO2 worldwide has increased from around 280 parts per million (ppm) or 0.028% to around 365 ppm, or 0.0365%. Although the increase may appear to be insignificant, the increase means that around 3 gigatons, or 3 billion metric tons of CO2, are being added to the atmosphere each year. Mathematically, the increase is around 30.4% and looking at the numbers this way, we can understand how therefore in reality it does affect earth more than we would expect it to. Since CO2 absorbs heat, more CO2 being released into the atmosphere means that the earth?s temperature should go up with corresponding increases in concentration of CO2 in the atmosphere. To confirm this fact, climatologists have detected a small but steady increase in the global average temperatures over the past few decades. Out of the last ten years, six set records for being the hottest years ever on record. The increase in the average global temperature over the past 140 years is reflected in Figure 3. I feel that given the current rate of change and the possible implications they could have on our world today, I feel that scientists are justified in being concerned about the current rate of change, instead of the changes themselves. This is because changes on a minor level would have minimal effect while if the rate of change accelerates at the speed it is now, then this could potentially be a problem. As shown by the steep upward curve towards the right side of all 3 Figures, the rate of change is accelerating quickly, and naturally this rate of change is a cause for concern to scientists, as drastic changes in the Earth?s climate could affect life on Earth as we know it. For example, the increase in concentration of CO2 in the atmosphere, which has already led to a parallel increase in temperature, could lead to a rise in the sea level and thus the flooding of low-lying areas. Also, with the greater temperature, the rate of evaporation will increase, leading to more precipitation. These changes could have a wide range of impacts, ranging from affecting crop yields, water quality, water supply, erosion of beaches to a loss of habitat and thus the extinction of a species. In conclusion, the Earth?s climate has always been changing, but never before at the rate of change we are now experiencing, in the areas of average global temperature, carbon dioxide emission and concentration of greenhouse gases in the atmosphere. As continued drastic changes in these areas could prove to be harmful towards the earth, I therefore conclude that it is indeed the rate of change that is of current concern to scientists. 2. Explain the process and impact of ?greenhouse effect?. Use relevant tables, figures, diagrams to illustrate your answer. You may like to use the following lead questions to guide you as you prepare for your answer. (i) What is greenhouse effect and how does it work? (ii) Why greenhouse effect is necessary for the planet Earth? (iii) What is ?enhanced greenhouse effect? (ege)? (iv) Why the discussion of greenhouse effect nowadays has negative connotations? The Greenhouse Effect The greenhouse effect is essentially the process by which the sun?s heat warms the earth?s atmosphere. More specifically, the greenhouse effect is a naturally occurring process which helps to heat the surface of the Earth, as well as its atmosphere, and is in fact necessary for our survival on Earth. As sunlight enters the Earth?s atmosphere, it passes through the many layers of greenhouse gases. When it reaches the Earth?s surface, land, water, and the biosphere absorb the sun?s heat. After being absorbed, the heat energy is reflected back into the atmosphere. While some of the heat passes back into space, most of it is trapped in the atmosphere by the greenhouse gases. Since the heat is trapped in our atmosphere, the average global temperature is raised. [image] Figure 4 Several greenhouse gases are found in our atmosphere (the exact distribution of these gases is shown in Figure 4), and they are characterized by their ability to absorb and reradiate this outgoing radiation, which effectively stores some of the heat in the atmosphere, thus producing a net warming of the surface. This process is known as the greenhouse effect. The greenhouse effect is created because some atmospheric gases, such as carbon dioxide, water vapor, and methane, are able to change the balance of energy on our planet by absorbing the longwave radiation emitted from the Earth?s surface. Figure 5 [image]The process of the greenhouse effect is as follows: as energy from the sun passes through the atmosphere, roughly a quarter of it (26%) is reflected or scattered back to space by clouds and other atmospheric particles. Another 19 % of the energy available is absorbed by clouds, and greenhouse gases and other particles in the atmosphere. Of the 55 % of the solar energy which actually manages to pass through the Earth?s atmosphere, about 51 % of the sun?s radiation reaches the surface while the final 4 % is reflected from the surface back into space. This is illustrated in Figure 5. The energy which reaches the earth?s surface is used for a number of purposes, including heating the ground surface, melting of ice and snow, evaporation and photosynthesis. The heating of the ground by sunlight causes the Earth?s surface to become a radiator of energy in the longwave band, also known as infrared radiation. This emission of energy is generally directed back to space, but only a small portion of this energy actually escapes, as most of the outgoing radiation is absorbed by the greenhouse gases. Since most of the longwave radiation into the atmosphere is absorbed by the greenhouse gases, there is extra heat energy added into the Earth?s atmospheric system. The heated atmospheric greenhouse gas molecules begin to radiate longwave energy in all directions, and a large portion (more than 90%) of this energy is radiated back to Earth, where it is absorbed by the surface. When the ground is heated by the longwave radiation, it once again radiates heat and the cycle above is repeated over and over until no more longwave is available. [image]This cycle is reflected in Figure 6. Figure 6 Why the Greenhouse Effect is necessary The Greenhouse Effect is necessary for our survival on Earth, as without it, the average global temperature of the Earth would be -18?C, instead of the present 15?C. As we have seen already, the greenhouse effect is the increase in temperature that Earth experiences because certain gases in the atmosphere, such as carbon dioxide and methane, trap the sun?s heat. Therefore, we can infer that if these gases were absent, heat would escape back into space and the Earth?s average temperature would be much colder. Hence, the natural greenhouse effect keeps the Earth?s surface much warmer than it would be if there was no atmosphere. The greenhouse gases in the atmosphere trap a lot of heat that would otherwise escape to space, raising the temperature. The Enhanced Greenhouse Effect Since the Industrial Revolution began around 200 years ago, mankind has been burning large quantities of fossil fuels. These fossil fuels release carbon dioxide and other greenhouse gases into the atmosphere, and hence more heat is trapped by the atmosphere, thus increasing the effects of the greenhouse effect. Since the process results in the natural greenhouse process being enhanced, the process is known as the enhanced greenhouse effect, or ege. ege is the direct result of human activities and is brought about in several ways. As mentioned already, the burning of fossil fuels is one of them. Other examples include industrial processes and deforestation, which reduces the amount of carbon dioxide removed from the air. In addition, deforestation also releases other greenhouse gases into the atmosphere, such as methane and nitrous oxide. [image]Man-made emissions of carbon dioxide are greater than the release of other greenhouse gases and have contributed the most to ege, about 62%. Other gases have contributed relatively lesser, with methane, nitrous oxide and CFCs contributing around 20%, 4% and 12% respectively. These numbers are illustrated in Figure 7 Figure 7 ege is believed by some scientists to be the cause of global warming. Over time, climate models have been used to detect changes and relationships in the climate. These models have been used to prove the link between greenhouse gas, pollution and global warming. Negative Connotations of the Greenhouse Effect The discussion of the greenhouse effect in the modern context tends to have negative connotations for several reasons. Firstly, the main reason why the greenhouse effect today has negative connotations is because it is often very closely associated with global warming. This association began in the mid 1950s, as the term ?greenhouse effect? began to be associated with global warming and also with the negative effects of the industrial age. This negative impact was later renamed to become the ege, as discussed earlier. Some examples of the effects of global warming include the rise in sea level and more common occurrences of droughts. Some time ago, some scientists began to paint a very gloomy and solemn picture of the Earth?s future, as a ?scorched and uninhabitable planet,? a planet whose ?oceans usurped coastal towns and villages? and whose ?fiery sun made deserts of once lush farmlands and pastures.? Although this image has changed in recent times as a more realistic picture is portrayed, the dangers still remain. 3. The discovery of fossil fuels is one of the most significant human accomplishments but its impact has also been one of the most damaging. Do you agree? Why? Fossil fuels were discovered in the early 1800s, and its discovery sparked off the Industrial Revolution. The 3 main types of fossil fuels are coal, oil and natural gas. Fossil fuels, which are found deposited in rock formations, were formed over a long period of time, many years ago. During that time, our Earth was much warmer, with a high concentration of carbon dioxide in the atmosphere. Photosynthetic organisms, such as algae and other plants absorbed the CO2 and produced large quantities of organic material. After those organisms died, their decayed remains were buried by sediments and compressed under the great force of the weight above them. Through the action of heat and pressure over many thousands of years, the remains were chemically transformed into the products we have today, namely coal, oil, and natural gas. The discovery of fossil fuels has proved to be one of the most significant in human history because since their discovery in the early 1800s, man has been burning large quantities of fossil fuels to aid the development of our technological and global civilization. By turning the energy trapped within them into heat which can be used for transportation, manufacturing and construction, the global industrial revolution was started, and this effectively changed our world forever. However, the overall impact of the discovery of fossil fuels has not been all good. The burning of fossil fuels leads to the emission of carbon dioxide into the atmosphere, as all fossil fuels release carbon dioxide when burned. This emission of carbon dioxide has already led to the enhanced greenhouse effect (ege), as discussed in question 2. Hence, the excessive use of fossil fuels worldwide has negatively affected the environment drastically. The CO2 released by the burning of these fossil fuels and the resultant increase in average global temperature could possibly have some very severe consequences as mentioned earlier. The burning of fossil fuels is also one of the main causes of air pollution, as caused by large-scale industrialization since the 1800s. Following the discovery of fossil fuels in the 1800s, man has been burning large quantities of fossil fuels to aid the development of our technological and global civilization. After weighing all the factors, I agree that the use of fossil fuels does produce benefits to us that could not be replicated using other methods and that the advantages they bring to us are too great to be ignored. However, I do feel that the excessive use of fossil fuels since their discovery has led to negative effects being produced, such is excessive amounts of carbon dioxide being released into the atmosphere, and causing the enhanced greenhouse effect. Therefore I feel that their impact has also been one of the most damaging. In conclusion, I agree that while the discovery of fossil fuels has been one of the most significant human accomplishments, its impact has indeed been one of the most damaging, because fossil fuels have been overused and hence negative impacts have been produced, the most notable of which is global warming.

The Changing Climate 9.7 of 10 on the basis of 3858 Review.