Ejercicio B · Inglés PAU Madrid Extraordinaria Coincidencias 2022

TEXTO B

Climate Change Is Making Earth Dimmer

Earth is reflecting less light as its climate continues to change, a new research suggests. This research relies on two decades' observations of a phenomenon called "earthshine" – which is the light that Earth reflects onto the surface of the dark side of the moon – and with satellite data of Earth's reflectivity and the sun's brightness. Different features on Earth reflect different amounts of light: the oceans very little, land about twice as much. Meanwhile, clouds reflect half the sunlight that hits them, and snow and ice reflect the majority of light they receive.

Scientists at Big Bear Solar Observatory in Southern California have been studying earthshine fluctuations since 1998. In this new research, scientists combined that data with observations from NASA’s Clouds and the Earth’s Radiant Energy System (CERES) project, operating since 1997, to get a sense of Earth's brightness change. Over the last two decades, the amount of light Earth reflected dropped about 0.5%, with most of the change coming in the last four years, showing an even sharper decline at its end.

During the same time, the brightness of the sun – which went through two periods of maximum activity and one quiet period – didn't meaningfully connect to Earth fall in reflectance. Therefore, the change in the amount of light Earth is reflecting must undoubtedly come from a change in Earth itself, the researchers reasoned.

In particular, the CERES data noted a decrease in the amount of bright low-altitude clouds over the Pacific Ocean, where scientists are also registering sharp temperature increases at the ocean surface. And because light not reflected out to space is trapped in the Earth system, the change in brightness has implications for the future of climate, potentially increasing the pace of human-caused climate change.

Adapted from “Climate change is making Earth dimmer,” Live Science, October 3, 2021. <https://www.livescience.com/climate-change-dimming-earth>

QUESTIONS

B.1.- Are the following statements TRUE or FALSE? Copy the evidence from the text. Use a complete sentence. No marks are given for only TRUE or FALSE. (Puntuación máxima: 2 puntos)

a)

Clouds, snow and ice reflect at least 50% of the light they receive from the sun.

TRUE

FALSE

b)

According to experts, Earth reflection evolution isn't exclusively due to Earth's own changes.

TRUE

FALSE

B.2.- In your own words and based on the ideas in the text, answer the following questions. Do not copy from the text. (Puntuación máxima: 2 puntos)

a)

How has Earth brightness changed in the last twenty years?

b)

Which two facts have been observed in the Pacific Ocean area?