Theories to Global Warming - Assignment Example

Chitra Ravichandran 24 May 2008 Global Warming Purpose There are 2 theories to Global warming Asserts that there has been a rise of about 0.9°C in the average temperature of the earth over the last century. 2) Argues that we are merely at the peak of a temperature wave and that the increase in temperature is not a cause for concern since it can only descend now onwards. The purpose of this report is to show that there is solid evidence to suggest that the first theory is right. Hence ,the effects of Global warming are alarming and a genuine cause for concern. Signs of Global warming : Impact on land Range of arable land expands south and north. Soil drier due to higher evaporation rates. Increased CO2 aids some plant growth. Habitats for some animals shrink. Range of insects likely to expand . [Spread of tropical diseases.] Impact on water Sea level rises due to melting ice caps, warming water. High water eats away at, or submerges, coastal land. Sea water contaminates some drinking water supplies. Water levels drop in some rivers, streams. [Intensifies damage from storms and droughts.] Impact on air Cloud cover increases Levels of the greenhouse gas methane may increase Hurricanes range farther north, south on warmer water. [Carbon dioxide in atmosphere doubles in the next century.](“Signs Of A Warming World”) Data description : Statistical data can be obtained from surveys, experiments or any series of measurements. In this case, we have used the 2 methods : 1.Survey 2.Series of measurements 1.Survey : 1.Do you agree that the average global temperature is going up? 2.Do you believe that the temperature of the earth has risen by about 1°C since 1850? 3.Do you think that the scientists who are talking about global warming as a glaring problem, are talking with valid evidence? 4.Do you think that human beings are responsible for this occurrence? 5.Do you think that there is an unnecessary hype about the whole issue of global warming? 6.Do you think that human beings will change their behavior to reduce the effects of this alarming phenomena? This was a simple questionnaire which a section of people in the age group 20-40 years were asked to answer. I took the sample size as 40 and incorporated random sampling. These are the findings of the questionnaire : Question No. No of people who said ‘Yes’ % of people agreeing 1 29 72.5 2 25 62.5 3 24 60 4 26 65 5 31 77.5 6 33 82.5 2.The second method involves the taking of “series of measurements” from CRU, UK. Time period : The values have been taken for the period 1960-2008. Type of sampling : “Sometimes it is cheaper to cluster the sample in some way e.g. by selecting respondents from certain areas only, or certain time-periods only. Cluster sampling is an example of two-stage sampling or multistage sampling: [in the first stage a sample of areas is chosen; in the second stage a sample of respondent within those areas is selected.]”(“Sampling (statistics)”) In 1850 the “Monthly mean central England temperature” is 9.10°C (T). (Monthly mean central England temperature (DEGREES C)) This data records the difference in temperature relative to the temperature as taken on 1850. This graph is a frequency histogram of the (T1-T) column in the above table. This shows that most of the values lie in the range 0.6-0.9.Later on in this project, we will be strengthening this theory by finding out the 95% confidence interval. Calculations : Based on our 2nd sample , We need to find a confidence interval for degree of confidence(1 – α) = 0.95.For this we have to calculate the following : 1) The mean is a way to describe the location of a distribution. It shows the average temperature difference between the particular year and the temperature in 1850. Calculation of mean(μ) = ∑( T1 – T) / N where N is the no. of years taken into consideration. In this case , N = 58. Mathematically , 58 μ = ∑( Ti – T) / N i=1 = (0.31 + 0.17 + 0 + 0.74 + ……+ 1.72 + 1.38)/58 = 0.602 Mean = 0.602 2) The variance is a way to capture its scale or degree of being spread out. Calculation of Variance (σ2) = ∑( T1 – μ)2 / N (It will not be N-1 as we are calculating the variance for a sample and not for an entire population). Mathematically , 58 σ2 = ∑( Ti – μ)2 / N i=1 = 20.04715/58 = 0.345015 3) The standard deviation is a measure of statistical dispersion of its values. Calculation of Standard deviation (σ) = √(Variance) σ = √0.345015 = 0.5874 4) The reliability of the mean as the estimate of μ is often measured by σX = σ / √N is called the standard error of the mean. Mathematically , σX = σ / √N = 0.5874 / √58 = 0.01013 5) Calculation of confidence interval for 1 – 0.05 = 0.95 degree of confidence : - zα/2 σ / √N < μ < + zα/2 σ / √N Now , P(-z ≤ Z ≤ z) = 1 – α = 0.95 α = 0.05 F(z) = P(Z ≤ z) = 1 – α/2 = 0.975 z = F-1(0.975) = 1.96 0.95 = P(-z ≤ Z ≤ z) = P(-1.96 ≤ ( - μ) σ / √N ≤ 1.96) = P( - 1.96 σ / √N ≤ μ ≤ + 1.96 σ / √N) = P(-1.96× 0.01013 ≤ μ ≤ + 1.96 × 0.01013) = P(-1.96× 0.01013 ≤ μ ≤ + 1.96 × 0.01013) = P( - 0.02 ≤ μ ≤ + 0.02) = 0.602 as it is the sample mean. Therefore , confidence interval is (0.602–0.02 , 0.602+0.02) Confidence interval = (0.582,0.622) Upper 95% confidence interval = 0.622 Lower 95% confidence interval = 0.582 The above interval shows that 95% of the (T1 – T) values fall in the range (0.582,0.622). Hence , we can conclude that the temperature in the last 50 years is certainly greater as compared to mid 1850s.This is a clear indication of a significant rise in temperature in this period. That is , recent temperatures are higher than those of the last century. Y(Temp) X Years This is a graph plotted with ‘year’ on the x-axis and ‘measured temperature’ corresponding to the year on the y-axis. It is very clear that taking into account even the last 58 years, the temperature of the earth has been rising steadily. Conclusion : Comparing statistical data obtained from the 2 methods, 1)The 1st survey method shows that there is still a section of people who are not aware about the factual figures regarding global warming and think that this is a much hyped subject and the issue is not a major cause for concern. 2)The 2nd method of obtaining statistical data(series of measurements) is in contradiction with the above observations. This asserts that there has been a rise of about 0.9°C in the average temperature of the earth over the last century. Indeed, the dynamics and dangers of global warming are alarming. Although the belief in, and concern about this subject is increasing, human beings need to further modify their behavior to nullify the effects of this frightening phenomena. Works Cited “Signs of A Warming World”. CNN.com. 27 November 1997. Cable News Network. 23 May 2008. . “Sampling (statistics)”. Wikipedia contributors. Wikipedia: The Free Encyclopedia. 214303295. 22 May 2008. 23 May 2008. “MONTHLY MEAN CENTRAL ENGLAND TEMPERATURE (DEGREES C)”. metoffice.gov.uk. 22 May 2008. Met Office. 23 May 2008. Read More