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Earth’s Changing Environment Lecture 11. Growth. Growth. Growth. Growth Rate. Growth Rate = % change/year World population increased from 6.079 billion in 2000 to 6.154 billion in 2001. This corresponds to a Growth Rate equal to 1.2%. US Population Growth. Current US Population:
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Earth’s Changing EnvironmentLecture 11 Growth Growth Growth
Growth Rate • Growth Rate = % change/year • World population increased from 6.079 billion in 2000 to 6.154 billion in 2001. • This corresponds to a Growth Rate equal to 1.2%.
US Population Growth • Current US Population: 293 million • Growth Rate = 0.87% • Population Growth = 0.0087x 293 million = 2.5 million • 2050 Population: 403 million
Global Population Growth • Current Global Population: 6.3 billion • Growth Rate = 1.15 % • Population Growth = 0.0115x 6.3 billion = 73 million • 2050 Population: 9.1 billion
Global Population GrowthMore/Less Developed Countries • Now • World: 6.3 billion • MDC: 1.20 • LDC: 5.10 • 2050 • World: 9.1 billion • MDC: 1.25 billion • LDC: 7.84 billion
Growth in Energy ConsumptionMDCs & LDCs • Now • World: 400 QBtu • MDC: 270 QBtu • LDC: 130 QBtu • 2050* • World: 800 QBtu • MDC: 320 QBtu • LDC: 480 QBtu * A mid-range prediction
Population growth increases environmental impacts • Increasing population and increasing energy consumption will accelerate: • depletion of fossil fuel resources • increasing pollution • declining biodiversity
Exponential Growth • Constant Growth Rate
Doubling Time • DT, the doubling time, is the time for something (population, energy consumption, pollution) to double. • DT (years) = 70 / Growth Rate (%) • If Growth Rate = 3.5%, DT = 70/3.5 = 20 years.
Growth in Energy Consumption • Growth rate = 3.4% • What’s the doubling time?
Growth in Energy Consumption • Growth rate = 1.6% • What’s the doubling time now?
Global Energy Consumption • Growth rate = 1.76% • What’s the doubling time?
Global Energy Consumption • Growth rate = 0.2 % • What’s the doubling time?
Another Calculation • During 2003, India consumed 13 QBtu of primary energy. • Suppose the growth of Indian energy consumption equals 5%. • What will be India’s consumption level in 2059? • DT = 70 / 5 = 14 years • 56 y / 14 y = 4 • Doubles 4 times: 2x2x2x2 = 16 • In 2059: 16 x 13 = 208 QBtu
Lifetime of a Non-Renewable • Lifetime (L) of a non-renewable Resource (R) with current consumption (C) increasing with a fixed growth rate (G): L = [Ln(G R/C + 1)]/G
Example: Oil • R = 2000 Gbo • C = 28 Gbo/year • G = 5% • L = 30 years • R = 4000 Gbo • L = 42 years • G = -1 % • L = 125 years
A note of caution • The doubling time calculation is very useful for estimating the effects of exponential growth, but it does not always lead to realistic predictions. If the growth rate is not constant, then growth will not be exponential.