Lab 8

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Georgia State University *

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1112

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Geography

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Oct 30, 2023

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Lab 8 Q1: For approximately how many thousands of years has the Earth been in the peak of an interglacial period within the present ice age? Between 15,000 and 10,000 years Q2: How much higher has the average temperature during the peak of the interglacial period been compared to the average temperature during the last glacial maximum? Last glacial max- 20,000 years ago. Temp -7.62 Peak interglacial period – about 10,000 years ago. Temp- 0.52 The average temp during the peak of interglacial period is about 7 degrees higher than the average temp of the last glacial maximum. Q3: In which hemisphere do you think this temperature reconstruction was based? I think it was in the Northern Hemisphere. Q 4: Why do you think most tree-ring sites are located in the middle and high latitudes and not in the tropics? Forests in middle and high latitudes have growing and dormant seasons. These seasons are needed for tree rings to form (a tree ring is produced during the growing season). Tropical forests grow year-round and don’t have a real dormant season. . Q5: Based on all the reconstructed temperatures (i.e., all those lines you see in the graph above), what 150-yr period appears to be about as warm as 1950-2000? The period between 950-1100 is about as warm as 1950-2000 Q6: Approximately how much warmer (e.g., 0.5° C, 1° C, 1.5° C, etc.) was the warmest 50-yr period than the coldest 50-yr period? It was about 1 degree warmer Q7: What do you think was the main factor that caused the temperature differences between the warmest and coldest 50-yr periods? I think the main factor was the change in the population of humans.

Q8: Based on the reconstructed total solar irradiance from the six studies, would you rate the research community’s confidence in the past TSI as low, medium, or high? Based on the data, I would rate the research community’s confidence in the past TSI as high. Q9: What century had much higher CO 2 concentrations than the other centuries and why? 1900- 2000 had higher CO2 concentrations because there were more humans, carbon emissions, and industrialization. Q10: During what century do you think anthropogenic sulphate aerosols scattered and reflected the most incoming solar radiation? I think anthropogenic sulphate aerosols scattered and reflected the most incoming solar radiation between 1900-2000 Q11: Based on the reconstructed temperatures you saw and changes in solar irradiance and CO 2 concentrations over the past millennium, what century do you expect to have the largest simulated temperatures from the GCMs? The twenty first century Q12: What are two possible reasons for why the 20 th century was the warmest century over the past millennium? Two possible reasons are the population increased, and more fossil fuel combustion. Q13: If the 20 th century did not have such high amounts of SO 2 emissions, how do you think the simulated temperatures would have differed from the temperatures in the above figure? I think the temperatures would be lower than the figure above if the 20 th century had lower SO2 emmissions Q14: During what two long periods (i.e., decades) did temperatures increase? One was 1930-1940 and the other was 1990-2000

Q15: During what long period did temperatures not increase? 1900-1910 Q16: What are the two most plausible reasons for why 1980-2000 was a warmer period than 1900-1920? 1) Increased CO2 concentrations from increased fossil fuel combustion 2) Increased SO2 emissions Q17: Why do you think there was not any global warming for approximately four decades (i.e., 1940 to 1980)? Increased SO2 emissions initiated a cooling effect that effects were eventually diminished by the warming effects of CO2 in the late 20th century. (Based on Changes in Temperature and Anthropogenic SO2 Graph). Q18: What is one way that sulphate aerosols increase Earth’s albedo? The aerosols make the clouds more reflective Q19: Which hemisphere had a substantially larger increase in SO 2 emissions from 1947 to 1976? Northern Q20: Based on the above findings for SO 2 emissions and the resulting concentrations of sulphate aerosols, which hemisphere is most likely to have not experienced warming from 1947-1976? Southern hemisphere

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Q21: How did the two hemispheres differ with respect to changes in temperature from 1947-1976? The two hemispheres differed inversely with respect to changes in temperature from 1947-1976 (Overall, the Northern Hemisphere’s temperature decreased and the Southern Hemisphere increased) Q22: Do you think the increase in concentrations of sulphate aerosols from 1947-1976 is a valid reason for the lack of global warming over that period? Explain why. Yes I do believe the increase in sulphate aerosols from 1947-1976 is a valid reason for the lack of global warming in that period. Upon further research, I found that most aerosols reflect light. While this assertion is dependent on the composition and color of the aerosol. Light particles reflect radiation towards space while darker aerosols can absorb insolation. The high concentration of sulphate aerosols during this period reflected light and insolation, causing the atmosphere to have a cooling effect. Q23: What environmental situation that was discussed in the Air Pollution lab resulted in a decrease in SO 2 emissions, and thus concentrations of sulphate aerosols, in the 1980s and 1990s? Feel free to search the Web. The passage of the Clean Air Act. Q24: What do you think was the primary cause of the increase in temperature from 1750 to 2011? Increases in human populations and the increased combustion of fossil fuels, industrialization, and CO2 emissions that encourage human population growth. Q25: What gas was the largest contributor to total radiative forcing from 1750 to 2011? CO2

Q26: What do you remember from Lab 2 (Stratospheric Ozone) about the effects of CFCs and HCFCs on the ozone layer? CFCs and HCFCs caused the Antarctic hole in the ozone layer. Q27: Why do black carbon and the direct effect of sulphate aerosols have opposite radiative forcings? Because they reduce albedo and reflect more insolation than they absorb. Q28: What four greenhouse gases had the largest positive radiative forcings among all the forcing agents? CO2, CH4 (METHANE), N2O (NITROUS OXIDES), HALOCARBONS (CFCS, HCFCS) How has the Sun caused changes in global and hemispheric temperatures over the past millennium? How did global temperatures change during the 20 th century? What evidence exists for carbon dioxide as the main cause of global warming from the pre-industrial times to the present? How has the Sun caused changes in global and hemispheric temperatures over the past thousand years? Answer: As the axial tilting of earth exposes the southern hemisphere more in the past thousand years there is melting of ice in the south pole that has reduced the albedo that causes the heat to be increased globally and more specifically in Southern hemisphere. Also, in the past thousand years the solar spot and flaring activity also influenced the temperature of the earth by exerting more direct radiation. There are a couple of ways that the sun has caused changes in temperatures over the past thousand years. One is the melting of ice in the south pole. Another is the solar spot and more direct radiation.

How did global temperatures change during the 20th century? Answer: In 20th century, global temperature increased by 0.6°C. This increase in temperate is because of more greenhouse gas emission, humans, and vehicles. These things cause the temperature of earth rise. What evidence exists for carbon dioxide as the main cause of global warming from the pre- industrial times to the present? Answer: During pre-industrial times, there were less cars and no industries so CO2 was not as high as it is now. After the industrial revolution, more greenhouse gasses and CO2 emissions caused the temperatures to rise.

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