1. Climate
Chapter 4
Section 1

2. Think about it
When you think about climate, you may think about big storms such as Hurricane Katrina, but big storms are better described as weather rather than climate. So, what is climate? How do climate and weather affected organisms and ecosystems?

3. Weather and climate
Weather is the day-to-day conditions of Earth’s atmosphere.
For example, it may be sunny one day and cloudy the next.
Climate is defined by year-after-year patterns of temperature and precipitation.
For example, the desert is typically dry and suffers from drought every year.
Microclimates are environmental conditions that can vary over small distances.
For example, south-facing sides of trees and buildings receive more sunlight and are usually drier than the north-facing sides.

4. Factors that affect climate
Global climate is shaped by many factors, including solar energy trapped in the biosphere, latitude, and the transport of heat by winds and ocean currents.
Ex: A person living in Orlando, Florida may wear shorts and a t-shirt in December, while a person living in Minneapolis, Minnesota is still wearing a heavy coat in April.

5. Solar energy and the greenhouse effect
Some of the energy we receive from the sun is reflected back into space, while some is absorbed and turned into heat.
Some of that heat goes back into space and some gets trapped in the biosphere.
The balance between the heat that stays in the biosphere and the heat that goes back into space determines the average temperature of the Earth.
Carbon dioxide, methane, and water vapor are called greenhouse gases, and they function like glass in a greenhouse.

6. Greenhouse effect
The phenomenon of allowing visible light to enter, but trapping heat, is called the greenhouse effect.
If the concentration of greenhouse gas rises, more heat gets trapped, so the Earth gets warmer.
If the concentration falls, more heat escapes and the Earth cools.
Without the greenhouse effect, Earth would be much cooler than it currently is.

8. Latitude and solar energy
Equatorial regions (places near the equator) are generally really warm because the sun is almost directly overhead at noon all year.
Earth’s climate zones are produced by an unequal distribution of the sun’s heat on Earth’s surface.
Polar regions, therefore, are going to receive much less solar energy than the tropical regions do.
The tilt of the Earth’s axis causes the distribution of sunlight to change over the course of the year.

9. Latitude and solar energy
The difference in heat distribution creates three different climate zones: tropical, temperate, and polar.
The tropical zone, or tropics, receives nearly direct sunlight all year long.
On either side of the tropical zone are the two temperate zones, and after the temperate zones come the polar zones.
Temperate and polar zones receive different amount of solar energy at different times.
During winter in the temperate and polar zones, days are shorter and solar energy is less intense.

11. Heat transport in the biosphere
The unequal distribution of heat across the globe is what creates wind and ocean currents.
These currents transport heat and moisture.
Warm air is going to rise, while cool air is going to sink. Earth’s currents cause winds to blow from west to east (generally) over the temperate zones, and from east to west over the tropics and the poles.