Question Answered by NOAA, Air Resources Laboratory, Field Research Division, Idaho Falls, ID
The Earth’s climate does vary over time due to factors such as the movement of continents, large-scale volcanic activity, changes in the Earth’s orbit, and variations in the Sun’s energy output. Because of these changing factors, there is not one fixed temperature that can be considered the “normal” surface temperature for the Earth. During the past couple of million years, orbital variations have produced a series of cold glacial periods (ice ages) and warmer interglacial periods. We are currently in an interglacial period that started around 12,000 years ago when orbital changes caused natural global warming. Changes in the Earth’s orbit are not expected to start a new glacial period for at least another 30,000 years.
All life forms including humans are adapted to the climates they have experienced in the recent past. Modern civilization has arisen entirely within the current interglacial period. Any rapid climate change—whether due to natural or human causes—can be highly disruptive to many forms of life. Within the last few decades scientists have come to understand that human activities are rapidly increasing greenhouse gas concentrations. The climate effects of these rising concentrations are starting to exceed natural climate variations. If the greenhouse gas concentrations continue their upward trend, a period of rapid climate change is likely both in this century and beyond. Climate change is not limited to temperature. It also affects precipitation patterns, winds, polar ice, and sea levels.
What is weather?
Weather: what’s happening to the atmosphere over a short period of time. Look outside right now. Is it sunny? Cloudy? Windy? Is it about to rain or snow?
These conditions are considered weather — something that is happening minute-to-minute, or day-to-day.
What is climate?
Climate: what’s happening to the atmosphere in a specific place over a long period of time (30 years or more). We can predict some areas in the world get a certain amount of rainfall in the summer, or other places in the world are usually hot or usually cold.
When you measure a weather pattern over a period of time to determine the average, that’s climate.
Measuring Changes in Climate
Earth’s climate changes over time. The amounts of different gases, ash, dust and pollen in the atmosphere changes, as does the temperature of Earth.
In snowy areas, such as the Arctic and Antarctic, or on glaciers, snowfall freezes each year leaving a layer of ice as a record of that year’s snowfall. The frozen water in this ice record can tell us the approximate temperature of the Earth when the snow fell. Bubbles of air can also be trapped in the ice when it is frozen. When analyzed, these small pockets of ancient air can tell us which gases and how much dust and dirt were in the air up to 800 000 years ago!
Ice cores are tubes drilled out from the ice, and can be up to two miles long. The ice cores are taken back to the laboratory so researchers can discover the information trapped inside.
To learn more (and make a tasty snack) try this totally cool activity!
Materials: water, freezer, plastic cup, carbonated lemonade, red food coloring, fruit juice with pulp, cocoa mix, mixing bowl
Layer One: Fill your cup about 1/3 cup of fruit juice. The pulp in the fruit juice represents pollen from plants that have been blown by wind into the atmosphere. Mix in a teaspoon of cocoa mix. This represents ash and dirt in the atmosphere from a volcanic eruption. Freeze this layer solid before moving to Layer Two.
Layer Two: Mix fruit juice and fizzy lemonade in the mixing bowl. The bubbles in the lemonade are bubbles of carbon dioxide gas that represents carbon dioxide gas in the atmosphere. Add the mixture to your cup until it is about 2/3 filled. Freeze this layer before moving to Layer Three.
Layer Three: Add carbonated lemonade and a drop of red food coloring. The food coloring represents a warming period. Freeze until completely solid.
When all three layers are frozen, you can eat your ice core treat.
Activity credit: https://blog.doublehelix.csiro.au/ice-core/