Checks and Balances

The energy that Earth soaks up from the Sun is more or less balanced by the energy that it radiates out into space, but only in the long term. Short-term imbalances can make the planet colder or warmer. These temperature changes can lead to mass extinctions, like the one that wiped out the dinosaurs 65 million years ago. Once the balance is upset, this can lead to other changes in Earth's climate system, which are called feedbacks. There are two types of feedback. Negative feedbacks resist temperature change by reducing the effects of the initial imbalance. Positive feedbacks enhance the initial imbalance, leading to a greater temperature change. Scientists are concerned that steadily rising global temperatures may trigger powerful positive feedbacks that make Earth a lot warmer in the coming decades, with serious

NEGATIVE FEEDBACKS

Some natural processes resist change. When intense sunlight warms the ocean surface, water evaporates and rises into the air as invisible water vapor. As it rises it cools and forms clouds, which shade the ocean so it cools down. Eventually evaporation and cloud formation stops, so sunlight can warm the ocean again. This is an example of negative feedback.

POSITIVE FEEDBACKS

When ice forms or snow falls, the dazzling white surface acts like a mirror. It reflects solar energy, so less heat is absorbed by the ground and more ice forms. This is called the albedo effect. It is an example of positive feedback, which promotes change rather

Absorbed by the atmosphere

Reflected by the clouds, aerosols, and atmosphere

Absorbed by the atmosphere

Reflected by the clouds, aerosols, and atmosphere m

Absorbed by the surface

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Reflected by the surface r-

JAMES LOVELOCK

British scientist James Lovelock is famous for his theory that living things regulate the climate and the chemistry of the atmosphere in their own interest. Over the long term, a web of negative feedbacks ensures that life survives, despite catastrophes that cause mass extinctions. The theory is named after Gaia, the Greek goddess of the Earth.

Outgoing longwave radiation

Radiated by greenhouse gases

TIPPING POINTS

Steady change can have sudden, dramatic effects. If a jug full of ice cubes is warmed up from 14°F (-10°C) at the rate of a degree or two an hour, nothing at all happens until the temperature rises to just above 32°F (0°C). Then all the ice cubes start melting. Climate scientists worry that rising global temperatures may pass similar tipping points, causing sudden changes and triggering positive feedbacks that accelerate the process.

Outgoing longwave radiation

Radiated by greenhouse gases

. Transmitted through the atmosphere

Absorbed by greenhouse gases

Radiated by greenhouse gases

Radiated , from surface

Absorbed by . the surface

Elliptical orbit,

Earth

Earth

Circular_

orbit orbital cycles

Earth's climate changes in regular cycles caused by variations in its orbit around the Sun. These are known as Milankovitch cycles, after the Serbian mathematician who calculated them. One 100,000-year cycle changes the planet's orbit from almost circular to elliptical, affecting its annual temperature range.

Vertical

Sun's rays

Vertical

Changing tilt of axis

Changing tilt of Equator

Changing tilt of axis

Changing tilt of Equator

TILTED EARTH

Every 24 hours, Earth spins around an axis that is currently tilted at 23.5° from vertical. The spin gives us night and day, while the tilt causes our winters and summers. But the tilt varies over a 42,000-year cycle, from 21.6° to 24.5°. This alters the way sunlight strikes the surface of the planet, changing the areas of the tropical and polar regions and affecting global air circulation.

Axis orientation drifts in a circle

Getting Started With Solar

Getting Started With Solar

Do we really want the one thing that gives us its resources unconditionally to suffer even more than it is suffering now? Nature, is a part of our being from the earliest human days. We respect Nature and it gives us its bounty, but in the recent past greedy money hungry corporations have made us all so destructive, so wasteful.

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