FIGURE 2.10 Sunlight warms the earth’s surface only during the day, whereas the surface constantly emits infrared radiation upward during the day and at night. (a) Near the surface without water vapor, CO2, and other greenhouse gases, the earth’s surface would constantly emit infrared radiation (IR) energy; incoming energy from the sun would be equal to outgoing IR energy from the earth’s surface. Since the earth would receive no IR energy from its lower atmosphere(no atmospheric greenhouse effect), the earth’s average surface temperature would be a frigid –18°C (0°F). (b)With greenhouse gases, the earth’s surface receives energy from the sun and infrared energy from its atmosphere. Incoming energy still equals outgoing energy, but the added IR energy from the greenhouse gases raises the earth’s average surface temperature about 33°C, to a comfortable 15°C (59°F). Fig. 2-10, p.37

Table 2-2, p.40

FIGURE 2.13 On the average, of all the solar energy that reaches the earth’s atmosphere annually, about 30 percent(30 ⁄ 100) is reflected and scattered back to space, giving the earth and its atmosphere an albedo of 30 percent. Of the remaining solar energy, about 19 percent is absorbed by the atmosphere and clouds, and 51 percent is absorbed at the surface. Fig. 2-13, p.41

FIGURE 2. 11Air in the lower atmosphere is heated from below FIGURE 2.11Air in the lower atmosphere is heated from below. Sunlight warms the ground, and the air above is warmed by conduction, convection, and infrared radiation. Further warming occurs during condensation as latent heat is given up to the air inside the cloud. Fig. 2-11, p.39

FIGURE 2. 14 The earth-atmosphere energy balance FIGURE 2.14 The earth-atmosphere energy balance. Numbers represent approximations based on surface observations and satellite data. While the actual value of each process may vary by several percent, it is the relative size of the numbers that is important. Fig. 2-14, p.42

Increasing CO2 Concentrations

Example of Predicted Pattern of Temperature Increase over 100 years

FIGURE 2.15 The elliptical path (highly exaggerated) of the earth about the sun brings the earth slightly closer to the sun in January than in July. Fig. 2-15, p.44

FIGURE 2.16 Sunlight that strikes a surface at an angle is spread over a larger area than sunlight that strikes the surface directly. Oblique sun rays deliver less energy (are less intense) to a surface than direct sun rays. Fig. 2-16, p.44

FIGURE 2.16 Sunlight that strikes a surface at an angle is spread over a larger area than sunlight that strikes the surface directly. Oblique sun rays deliver less energy (are less intense) to a surface than direct sun rays. Fig. 2-16a, p.44

FIGURE 2.16 Sunlight that strikes a surface at an angle is spread over a larger area than sunlight that strikes the surface directly. Oblique sun rays deliver less energy (are less intense) to a surface than direct sun rays. Fig. 2-16b, p.44

FIGURE 2.17As the earth revolves about the sun, it is tilted on its axis by an angle of 231⁄2°. The earth’s axis always points to the same area in space (as viewed from a distant star). Thus, in June, when the Northern Hemisphere is tipped toward the sun, more direct sunlight and long hours of daylight cause warmer weather than in December, when the Northern Hemisphere is tipped away from the sun.(Diagram, of course, is not to scale.) Fig. 2-17, p.45

Table 2-3, p.46

FIGURE 2.19 During the Northern Hemisphere summer, sunlight that reaches the earth’s surface in far northern latitudes has passed through a thicker layer of absorbing, scattering, and reflecting atmosphere than sunlight that reaches the earth’s surface farther south. Sunlight is lost through both the thickness of the pure atmosphere and by impurities in the atmosphere. As the sun’s rays become more oblique, these effects become more pronounced. Fig. 2-19, p.46

FIGURE 2.22 The changing position of the sun, as observed in middle latitudes in the Northern Hemisphere. Fig. 2-22, p.50