Earth’s Changing Environment Lecture 11 Growth

Growth Rate Growth Rate = % change/year World population increased from billion in 2000 to billion in This corresponds to a Growth Rate equal to 1.2%.

US Population Growth Current US Population: 293 million Growth Rate = 0.87% Population Growth = x 293 million = 2.5 million 2050 Population: 403 million

Global Population Growth Current Global Population: 6.3 billion Growth Rate = 1.15 % Population Growth = x 6.3 billion = 73 million 2050 Population: 9.1 billion

Global Population Growth More/Less Developed Countries Now World: 6.3 billion MDC: 1.20 LDC: World: 9.1 billion MDC: 1.25 billion LDC: 7.84 billion

Growth in Energy Consumption MDCs & 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

What is the carrying capacity of the Earth?

Population growth increases environmental impacts Increasing population and increasing energy consumption will accelerate: depletion of fossil fuel resources increasing pollution declining biodiversity

US Energy Consumption ?

Arab Oil Embargo of 1973

Exponential Growth Models

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?

Exponential Growth Models

Growth in Energy Consumption Growth rate = 1.6% What’s the doubling time now?

Per Capita graph shows the effect of population growth

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.