What Causes The Change in Earth's Climate?

Sometimes, Britain has been hot enough for hippos to live in Norfolk. On other occasions, ice has covered the country for tens of thousands of years. Global climate change has generally occurred very slowly for thousands or millions of years. Today our climate is changing rapidly in comparison.

These are some of the factors that can make the Earth's climate warm or cool:

• Strength of the sun

Almost all the energy that affects the climate on Earth originates in the Sun. The energy emitted by the sun passes through space until it reaches Earth's atmosphere. Only about 40 percent of the solar energy intercepted in the upper part of the atmosphere passes to the surface of the Earth. The rest is reflected or absorbed by the atmosphere. The energy output of the sun is not constant; it varies with time and has an impact on our climate.

• Changes in Earth's orbit

The orbit of the Earth around the Sun is an ellipse, not a circle, but the ellipse changes shape. Sometimes it is almost circular, and the Earth stays approximately the same distance from the Sun as it moves around its orbit. At other times, the ellipse is more pronounced, so that the Earth moves closer and farther from the Sun while it orbits. When the Earth is closer to the sun, our climate is warmer.

• Changes in the orientation of the axis of rotation of the Earth

The Earth revolves around an axis (imagine a line joining the north and south poles) but the Earth's axis is not vertical, but inclines at an angle. This angle changes over time and for approximately 41,000 years it moves from 22.1 degrees to 24.5 degrees and vice versa. When the angle increases, the summers become warmer and the winters become colder.

• Amount of Greenhouse gases in the Atmosphere

These include carbon dioxide, methane and water vapor. Of these three, water vapor makes the greatest contribution to the greenhouse effect because there is more. These gases trap solar radiation (electromagnetic radiation emitted by the Sun) in the Earth's atmosphere, which makes the climate warmer.

• Carbon dioxide content of the oceans

Oceans contain more carbon dioxide (CO₂) than the atmosphere and can also absorb CO₂ from the atmosphere. When CO₂ is in the oceans, it does not trap heat as it does when it is in the atmosphere. If CO₂ leaves the oceans and returns to the atmosphere, this can contribute to a warmer climate.

• Plate tectonics and volcanic eruptions

Over time, the processes of plate tectonics cause continents to move to different positions in the world. For example, Britain was close to the equator 300 million years ago, and therefore was warmer than today. For more details, check our weather poster or online map. The movement of the plates also causes volcanoes and mountains to form and these too can contribute to a change in climate. Large mountain ranges can influence the circulation of air around the world and, consequently, influence the climate. The hot air can be diverted somewhere cooler by the mountains. Volcanoes affect the climate through gases and dust particles released into the atmosphere during eruptions. The effect of volcanic gases and dust can heat or cool the surface of the Earth, depending on how sunlight interacts with the volcanic material.

• Ocean currents

Ocean currents carry heat around the Earth. The direction of these currents can change so that the different areas become cooler and colder. The oceans store a large amount of heat, so that small changes in ocean currents can have a great effect on the coastal and global climate.

By: Preeti Narula

Content: https://www.bgs.ac.uk/discoveringGeology/climateChange/general/causes.html