The conversationAugust 10, 2021 2:31:45 pm ES
You probably remember that your elementary school science teachers explained that energy cannot be created or destroyed. That is a fundamental property of the universe.
However, energy can be transformed. When the sun’s rays hit Earth, they transform into random movements of molecules that are felt as heat. At the same time, the Earth and the atmosphere are sending radiation into space. The balance between incoming and outgoing energy is known as the Earth’s “energy budget.”
Our climate is determined by these energy flows. When the amount of energy going in is greater than the energy going out, the planet heats up.
That can happen in a number of ways, such as when the sea ice that normally reflects solar radiation back into space disappears and the dark ocean absorbs that energy. It also occurs when greenhouse gases accumulate in the atmosphere and trap some of the energy that would otherwise have been radiated.
Scientists like me Has been measure the Earth’s energy budget since the 1980s using instruments on satellites, in the air and oceans, and on land. It is an important part of the new United Nations climate assessment. Report of the Intergovernmental Panel on Climate Change released on August 9, 2021.
Here’s a closer look at how energy flows and what the energy budget tells us about how and why the planet is warming.
Balance of the sun’s energy
Virtually all of the energy in Earth’s climate system comes from the Sun. Only a small fraction is driven up from inside the Earth.
On average, the The planet receives 340.4 watts of sun per square meter.. All the sun goes down during the day, and the numbers are much higher at local noon.
Of those 340.4 watts per square meter:
- Clouds, dust, snow, and the Earth’s surface reflect 99.9 watts out into space.
- The remaining 240.5 watts are absorbed, about a quarter by the atmosphere and the rest by the planet’s surface. This radiation is transformed into thermal energy within the Earth system.
Almost all the absorbed energy corresponds to the energy emitted into space. However, a residue is now accumulating as global warming. That residual has risen, from just under 0.6 watts per square meter at the end of the last century to 0.79 in 2006-2018, according to the latest data from the Intergovernmental Panel on Climate Change. The vast majority of that is warming the oceans. While it may seem like a small number, that energy adds up.
The atmosphere absorbs a lot of energy and emits it as radiation both to space and to the planet’s surface. In fact, the Earth’s surface receives almost twice as much radiation from the atmosphere as it does from direct sunlight. This is mainly because the sun heats the surface only during the day, while the warm atmosphere is there 24/7.
Together, the energy reaching the Earth’s surface from the Sun and from the atmosphere is about 504 watts per square meter. The surface of the Earth emits about 79 percent of that amount. The remaining surface energy is used to evaporate water and heat the air, oceans and land.
The residue between incoming sunlight and outgoing infrared is due to the accumulation of Greenhouse gases as carbon dioxide in the air. These gases are transparent to sunlight but opaque to infrared rays – They absorb and emit a large amount of infrared rays downwards.
The temperature of the Earth’s surface must rise in response until the balance between incoming and outgoing radiation is restored.
What does this mean for global temperatures?
Doubling the carbon dioxide would add 3.7 watts of heat per square meter from the earth. Imagine old-fashioned incandescent night lights spaced every 3 feet around the world, leaving them on forever.
At the current rate of emissions, greenhouse gas levels would double from pre-industrial levels by mid-century.
Climate scientists calculate that adding so much heat to the world would warm Earth’s climate by about 5 degrees Fahrenheit (3 C). To prevent this, it would be necessary to replace the combustion of fossil fuels, the main source of greenhouse gas emissions, with other forms of energy.
Earth’s energy budget is at the heart of the new IPCC climate assessment, written by hundreds of scientists reviewing the latest research. With the knowledge of what is changing, everyone can make better decisions to preserve the climate as we know it.
Scott denning, Professor of Atmospheric Sciences, Colorado State University. This article is republished from The conversation under a Creative Commons license. Read the Original article.