41. Over the past 50 yrars, what has happened to Co, levels in the atmosphene? C

Question

41. Over the past 50 yrars, what has happened to Co, levels in the atmosphene? CNote stands for "parts per mallion") a) C, levels have steadily decreased by about 30% from ~375 ppm to ~310 ppm. cycled between about 310 ppm and about 375 ppm. just a bit outside the range of expected natural variation. c) CO, levels have remained relatively steady at about 340 ppm. d) CO2 levels have steadily increased by about 33% from-310 ppm to 00 ppm. 42. According to the ice core records, the atmospheric concentration of carton dioxide (CO) and other greenhouse gases is a) at its lowest levels of the past 800,000 years. b) still within the range of natural variations over the past 800,000 years. e) approaching the upper limit of natural variations over the past 800,000 years. d) now at the highest levels Earth has seen in the past 800,000 years 43. Although Scientists have been able to show that greenhouse gas concentrations are at historically high levels in the atmosphere, they have not yet been able to show that the increase in greenhouse gases is due to human as opposed to natural causes a. TRUE b. FALSE 44. As the climate begins to warm, an example of a negative (or balancing) feedback efleer would be: a) The warmer air absorbs more water vapor causing the climate to warm even more Glaciers begin to melt, thus reflecting less sunlight back out to space and causing the climate to warm even more b) e) d) Arctic tundra begins to thaw releasing methane gas (CH,) and increasing the greenbouse Plants grow faster, thus absorbing more atmospheric CO, and reducing the greenhouse effect. effect 45. In the climate system, positive (reinforcing) feedbacks are good whereas negative (balancing) feedback effects are bad. a) TRUE b) FALSE 46. In general, the climate models that scientists have developed have been reasonably successful in reproducing and predicting the major characteristics of climate change. a) TRUE. b) FALSE 7. Before the rise of modern civilization, the main variable driving the Ice Ages was: a. Natural fluctuations in carbon dioxide in the atmosphere. b. Fluctuations in other greenhouse gases in the atmosphere. c.Fluctuations in the solar energy reaching the northern hemisphere due to variations in the tilt, wobble, and ellipticity of Earth's orbit. d. Variations in volcanic activity

Explanation / Answer

41] Option d is correct

The amount of carbon dioxide going into the atmosphere as a result of human activities has been fairly steadily increasing over recent decades. Carbon dioxide emissions from cement and burning fossil fuels, for example, are estimated to have increased by nearly 30 per cent between 2000 and 2009.

But not all of the carbon dioxide humans emit remains in the atmosphere. Scientists have identified a number of natural ‘carbon sinks’ – forests and oceans, for example – which are able to re-absorb some of it. Different sinks can lock away carbon for anything from years to thousands of years.  

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