Today is Friday, January 5, 2024.
Have you already heard about the albedo?
The net sunlight reaching the Earth's climate system depends on the solar irradiance and the Earth's reflectance, the albedo.
And as we know from our daily clothes choices, black is warmer than white. This is because black absorbs light and white reflects it. This is why snow and ice shines.
Similarely, what happens when Earth's North and South Poles have less (white shining) ice sheets and more (black deep dark) water exposed?
The first precise and regular satellite measures of terrestrial albedo came with CERES - Clouds and the Earth’s Radiant Energy System - one of the five instruments onboard Terra spacecraft. Terra is a flagship mission from NASA’s Earth Observing System that began collecting data in early 2000.
Terra’s mission is to explore the connections between Earth’s atmosphere, land, snow and ice, ocean, and energy balance to derive a better understanding of the planet’s climate and climate change, along with the impact of human actions on these processes.
According to the new study in the AGU journal Geophysical Research Letters the Earth is now reflecting about half a watt less light per square meter than it was 20 years ago, with most of the drop occurring in the last three years of earthshine data. Earth reflects about 30% of the sunlight that shines on it and the reduction is equivalent of 0.5% in the Earth's reflectance.
According to the study, "neither the globally averaged inter-annual variations nor the long-term trend in Earth's reflectance that we measure show a correlation with either the solar cycle (sunspot number), the cosmic ray flux, or any other solar activity indices". So that means changes in Earth's reflectiveness are caused by something on the Earth.
According to a scientist at the University of California, many had hoped that a warmer Earth might lead to more clouds and higher albedo, which would then help to moderate warming and balance the climate system, but what is happening is the opposite.
Click at the image below to read the scientific study at American Geophysical Union / John Wiley & Sons.
You may also like the article Missing Heat, from Earthdata / Open Access for Open Science by NASA.
It starts as follows:
"When the mercury thermometer was invented in 1714, it took the scientific world by storm. On his transatlantic crossing in the year 1724, Benjamin Franklin recorded water temperatures by periodically dipping a thermometer into the ocean. By 1850, weather stations across the globe had gleaned a record of air temperatures over land. For the first time, scientists could track Earth’s temperature. And over time, it became clear that temperature was rising."
About temperature fluctuations, scientists indicate that one should look "at the entire energy balance: how much sunlight enters Earth’s atmosphere, how much of this energy is reflected and emitted back out to space, and where energy—in the form of heat—is being stored in Earth’s climate system ... Air, land, and water absorb and release heat at different rates, and on vastly different time scales". Not to mention high atmosphere and deep sea phenomena, El Niños and La Niñas, volcanic eruptions and greenhouse gases. The article analyses all that.
