1. 2. 3. 4. 5. Use the ice core record from Antarctica (below) to identify the r
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Use the ice core record from Antarctica (below) to identify the range of atmospheric carbon dioxide concentrations for the last 400,000 years Temperature and CO2 concentration in the atmosphere over the past 400 000 years (from the Vostok ice core CO2concentration, ppmv 300 280 260 240 220 200 180 160 400 000 350 000 300 000 250 000 200 000 150 000 100 000 50 000 Year before present (present 1950) Temperature change from present, c 4°C 2°C 0°C 2 C 4°C 6°C -8°? -10°C 400 000 350 000 300 000 250 000 200 000 150 000 100 000 50 000 Year before present (present 1950) GRID Areadal UNEP Sourc JR. Petit J Jouzel, et al. Climato and at sphe ich ory othe past 420 000 y a 3 f on the Vostok ico core in Anta ca, Natue 399(?? pp 429-436, 1999. O 120-300 ppm O -10 to 2 oC O 180-350 ppb O 180-300 ppmExplanation / Answer
1. As shown in the graph, the range (maximum and minimum values) of carbon dioxide concentration over the past 400,000 years was from 180 to 300 parts per million. The values neither exceeded 300 ppm nor were less than 180 ppm. Hence, the correct option is 180 - 300 ppm
2. The carbon dioxide reached a concentration of 400 ppm during 2016 as per the data released by the Mouna Loa Observatory in Hawaii. The concentration has not yet reached a value of 452 or 632 ppm. Hence, the correct option is 403 ppm.
3. The obliquity cycle is one of the orbital cycles which explains the effect of the axial tilt on long-term climate change. Diagram A shows the changes in tilt, i.e. the obliquity cycle. Diagram B shows the change in axial precession, i.e. the precessional cycle. Diagram C shows the change in orbit from elliptic to circular, i.e. the eccentricity cycle. Hence, the correct option is A.
4. A decrease in solar luminosity would cause global temperatures to decrease as the Sun is the primary source of heat. A decrease in carbon dioxide and methane would also cause global temperatures to decrease as the positive feedback of such greenhouse gases on the climate will be reduced. An increase in atmospheric sulfate aerosols would favor the formation of more clouds and effectively decrease global temperatures. A large decrease in the ice covering the Earth's surface would decrease the amount of reflected radiation and lead to an increase in the global temperatures. Hence, the correct option is large decrease in ice covering Earth's surface
5. Paleoclimate records are useful for attributing past climate variability to natural factors such as orbital cycles. The rate of increase or decrease in past climate variables such as temperature is compared with the present-day changes thus enabling us to identify the causes of the changes. The past records can precisely show how such climate variables changed with changes in carbon dioxide concentration, solar luminosity, aerosols etc. The data from paleoclimate records are also used for assessing computer models that are meant to provide information on future climate and to check whether such models are effectively simulating the past climate variability or not. Hence, all of the above options are correct.
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