Planetary Systems, Climate Change, Water Cycle and Biodiversity

Demographic Explosions

1670 (year) — 500,000,000 inhabitants; 1810 — 1,000,000,000; 1930 — 2,000,000,000; 1975 — 4,000,000,000; now — stagnant.

Systems Theory

Systems theory: a microscope for nearby objects and a telescope for the most distant; the macroscope will bring us closer to complex relationships hitherto unattainable.

Relationship Between Humans and Nature — Gaia

Relationship between man and nature. Gaia: The Gaia hypothesis interprets nature as a complex interrelationship between environmental systems that together form a kind of self-regulated superorganism. Global warming or alterations of ocean circulation may be adaptive reactions of the whole planet in response to environmental pressures.

Atmosphere and Earth's Thermal Balance

The atmosphere and the thermal balance of the Earth: The energy incident on Earth is primarily radiant, responsible for color vision and for the activity of photosynthetic algae and plants. Some incident energy is reflected by the surface (albedo); the remainder returns into the atmosphere as infrared radiation, which is dissipated as heat and warms the atmosphere. Elements that alter the path of intercepted radiation include:

• clouds
• suspended solid particles
• aerosols
• greenhouse gases

Weather and Climate Change

Weather: a difficult scientific model. The climate has always changed and will continue changing. Evidence about human influence on climate is varied. Atmospheric concentrations of CO₂ have risen by more than 30%. Humanity affects the climate by generating heat and warming the atmosphere.

Human Atmospheres

The human atmospheres: Increased atmospheric density in urban areas can inhibit heat escape. This density is often due to the presence of liquid and solid particles in suspension. Urban warming is understandable because buildings and paved surfaces retain heat like radiators. High concentrations of ozone gas are toxic and irritating and reduce visibility. Ozone is also produced by photochemical smog or haze in large cities.

Residence Time of Water

The residence time: the average time that a given amount of water remains in a compartment of the hydrosphere. A water molecule can remain trapped for millions of years in a polar ice cap or in the deep ocean, and several hundred thousand years in a subterranean aquifer. Only a few days are spent in a river or the atmosphere. These data show us how we should manage water resources.

The Water Cycle

The water cycle: The hydrologic cycle is the set of transport processes by which approximately 40,000 cubic kilometers of water are mobilized annually between the oceans and the continents. The primary pathway out of continental systems is ocean evaporation.

Biodiversity

Biodiversity: is a measure of the number of species living in a particular place relative to the total number of individuals in the community. The number of individuals is determined by food availability and the carrying capacity of natural systems. There are estimated to be between 3 and 50 million species. Humans began to affect biodiversity through hunting, expansion into new areas of occupation, and access to new resources.