The planet we live on: The beginnings of the Earth Sciences

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Figure 3.27: Global temperature changeover the last 2000 years, compiled from10 different sources (shown in differentcolours), including tree ring and glacialdata.Figure 3.28: <strong>The</strong> amount of carbon dioxidein the Earth’s atmosphere over the past40,000 years and (inset) the last 1000 years,measured from the bubbles of air trappedin ice cores.changed greatly, by as much as 10 ◦ C bet<strong>we</strong>en the warmest and coldest periods. It alsoshows that in geologically recent times, over the last 10,000 years, temperature has remainedparticularly stable. This is important is it is the time in which most of humanhistory has taken place; such developments might not have been possible if the temperaturehad not been so stable.This is why there is such concern over the recent global warming shown in Figure 3.27.This graph shows that recent temperatures have been 0.3 ◦ C warmer than at any time inthe last 2000 years and that this temperature increase is increasing.Temperature increases in the past have been associated with a similar increases in theamount of carbon dioxide in the atmosphere, as shown in Figure 3.28. Ho<strong>we</strong>ver, whetherthe increase is forcing (or causing) the climate change is still being debated.Nowadays that fact that both Earth’s temperature and the carbon dioxide content ofthe atmosphere have increased over the past 200 years, and are continuing to increase,is not disputed by the majority of scientists. Most scientists also think that the increasein carbon dioxide in the atmosphere is linked to the extensive burning of fossil fuels, likecoal and oil, since the industrial revolution began, 200 years ago.<strong>The</strong> carbon dioxide in the atmosphere is part of the complex carbon cycle and hugeamounts of carbon, cycle through the Earth’s systems annually. Plants absorb carbondioxide and release oxygen during photosynthesis whilst all respiring organisms, plantsand animals, have the opposite effect, absorbing oxygen and releasing carbon dioxide.This means that the amount of plant cover on Earth affects the amount of carbon dioxidein the atmosphere, which is why people are concerned about the felling of the tropical rainforests. After deforestation, the Earth’s surface can absorb less carbon dioxide, leavingmore in the atmosphere.91
Figure 3.29: A computer generated prediction for the global effects of a 3 ◦ C increase inglobal temperature.While most scientists think that the increase of carbon dioxide is the cause of the globalwarming, some scientists think that global warming is causing the increase of carbondioxide. This is an area of continuing debate by climate scientists. Ho<strong>we</strong>ver, manypoliticians now believe that impact of the burning of fossil fuels must be reduced, toreduce the amount of greenhouse gases being released into the atmosphere, and so reducethe effects on global warming.<strong>The</strong>re is still much debate over the effects that global warming might have. Clearly thewhole globe would become warmer, but computer-based climate models, based on flows ofthe ocean and atmosphere (such as in Figure 3.29), suggest that some parts of the Earthwould become much hotter whilst others might stay much the same temperature.Nevertheless, changes like these would have dramatic effects on Earth’s climate, withpredictions that Earth’s <strong>we</strong>ather would become more stormy and that the extent andintensity of drought areas would increase. Such <strong>we</strong>ather changes would affect water andfood supplies and so would directly affect humanity.Such warming would cause ice sheets to melt. If the floating ice sheets on the oceansmelted, global sea level would not change, since water from melting ice occupies a smallervolume than the ice itself. Ho<strong>we</strong>ver, if the ice sheets on land melted, all the water trappedas ice on the continents above sea level would flow into the sea, causing rises in sea level.Meanwhile, as the ocean waters warm, they expand, further increasing the volume of theoceans. Figure 3.30 shows that if the current trend of continental ice sheet melting andsea level rise continues, sea level is predicted to rise bet<strong>we</strong>en 20 and 60 cm by 2100.92
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Basic Books in ScienceBook 6<strong
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BASIC BOOKS IN SCIENCE- a Series of
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BASIC BOOKS IN SCIENCE- a Series of
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Looking ahead - If you came across
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3.2 Plate tectonics (20th Century)
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1.30 Coal seams in an opencast coal
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3.4 Alfred Wegener, the polar explo
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5.14 A GPS remote volcano monitorin
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Figure 1.2:minerals.A sandstone roc
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Even diamond can have different col
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Figure 1.8: A red garnet crystal in
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Figure 1.12: Crystals of minerals i
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Hematite, Fe 2 O 3 - earthy red, me
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Figure 1.17: Sedimentary rocks show
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Figure 1.20: A close up view of a p
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Figure 1.26: Ancient wave ripple ma
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Figure 1.30: Coal seams in an openc
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Figure 1.32: Close up view of a pie
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Figure 1.35: A fossil colonial cora
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Figure 1.38: Fossil ammonites, indi
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Figure 1.39: ‘Massive’ igneous
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Figure 1.41: A close up view of a p
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Figure 1.44: A basalt flow that coo
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Figure 1.47: Deposit of volcanic as
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Figure 1.49: An old slate quarry, s
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Figure 1.51: Slate, a low-grade met
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Figure 1.53: Schist, a medium-grade
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Page 71 and 72: Chapter 2Reading landscapes: how la
Page 73 and 74: Figure 2.3: Rock fragments loosened
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Page 89 and 90: Figure 3.3: James Hutton, the ‘Fo
Page 91 and 92: Figure 3.5: A page of Wegener’s 1
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Figure 6.6: Groundwater flowing out
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Dam disaster in Italy, when the wav
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Figure 6.10: A slab foundation, bui
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An example of this is investigation
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GlossaryAbsolute age The</s
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Carbon capture The
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Crustal shortening This results of
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Evaporite deposits (or evaporites)
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Geophysical survey Using the method
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“Integrated waste management” <
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Metamorphism The r
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Pore spaces (or pores) Gaps bet<str
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Saltation Sediment movement by flui
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Suspension Sediment movement by flu
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AcknowledgementsPermission to repri
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Figure 2.3 A scree slope. Photo ID:
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Figure 1.15a Hematite.Figure 1.15b
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Figure 1.28 Dune cross bedding in s
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Figure 3.18 An island arc volcano,
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Figure 5.21 Excavations at the dino
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