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Climate Change Causing Drop In Brightness Of Earth: Study

Two things affect the net sunlight reaching the Earth- the Sun’s brightness and the planet’s reflectivity, say experts

Climate Change Causing Drop In Brightness Of Earth: Study
  • Earth reflects about 30 per cent of the sunlight that shines on it: Experts
  • Experts studied decades of measurements of earthshine
  • A warmer Earth might lead to more clouds: Study

Washington: Warming ocean waters have caused a drop in the brightness of the Earth, according to a study which found that our planet is now reflecting about half a watt less light per square metre than it was 20 years ago. The study, published in the journal Geophysical Research Letters, used decades of measurements of earthshine — the light reflected from Earth that illuminates the surface of the Moon.

Also Read: World Facing COVID-19, Fragility, Conflict, Climate Change; We’re At Turning Point: UNGA

The researchers also analysed satellite measurements, finding that there has been a significant drop in Earth’s reflectance, or albedo, over the past two decades. They found that Earth is now reflecting about half a watt less light per square metre than it was 20 years ago, with most of the drop occurring in the last three years of earthshine data. That is the equivalent of 0.5 per cent decrease in the Earth’s reflectance, according to the researchers. Earth reflects about 30 per cent of the sunlight that shines on it, they noted.

The albedo drop was such a surprise to us when we analysed the last three years of data after 17 years of nearly flat albedo, said Philip Goode, a researcher at New Jersey Institute of Technology and the lead author of the study.

Mr Goode was referring to the earthshine data from 1998 to 2017 gathered by the Big Bear Solar Observatory in Southern California. When the latest data were added to the previous years, the dimming trend became clear, the researchers said. They noted that two things affect the net sunlight reaching the Earth: the Sun’s brightness and the planet’s reflectivity.

The changes in Earth’s albedo observed by the researchers did not correlate with periodic changes in the Sun’s brightness, meaning changes in Earth’s reflectiveness are caused by something on the Earth. There has been a reduction of bright, reflective low-lying clouds over the eastern Pacific Ocean in the most recent years, according to satellite measurements made as part of NASA’s Clouds and the Earth’s Radiant Energy System (CERES) project.

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That is the same area where increases in sea surface temperatures have been recorded because of the reversal of a climatic condition with likely connections to global climate change, according to the researchers. The dimming of the Earth can also be seen in terms of how much more solar energy is being captured by Earth’s climate system, they said.

Once this significant additional solar energy is in Earth’s atmosphere and oceans, it may contribute to global warming, the researchers explained. This is because the extra sunlight is of the same magnitude as the total anthropogenic climate forcing, or a number of human-induced factors, over the last two decades, they added. “It’s actually quite concerning,” said Edward Schwieterman, a planetary scientist at the University of California at Riverside who was not involved in the study. Many scientists 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, he said. “But this shows the opposite is true,” Mr Schwieterman added.

Also Read: U.N. Says World Likely To Miss Climate Targets Despite COVID Pause In Emissions

(Except for the headline, this story has not been edited by NDTV staff and is published from a syndicated feed.)

NDTV – Dettol have been working towards a clean and healthy India since 2014 via Banega Swachh India initiative, which is helmed by Campaign Ambassador Amitabh Bachchan. The campaign aims to highlight the inter-dependency of humans and the environment, and of humans on one another with the focus on One Health, One Planet, One Future – Leaving No One Behind. It stresses on the need to take care of, and consider, everyone’s health in India – especially vulnerable communities – the LGBTQ populationindigenous people, India’s different tribes, ethnic and linguistic minorities, people with disabilities, migrants, geographically remote populations, gender and sexual minorities. In wake of the current COVID-19 pandemic, the need for WASH (WaterSanitation and Hygiene) is reaffirmed as handwashing is one of the ways to prevent Coronavirus infection and other diseases. The campaign will continue to raise awareness on the same along with focussing on the importance of nutrition and healthcare for women and children, fight malnutrition, mental wellbeing, self care, science and health, adolescent health & gender awareness. Along with the health of people, the campaign has realised the need to also take care of the health of the eco-system. Our environment is fragile due to human activity,  that is not only over-exploiting available resources, but also generating immense pollution as a result of using and extracting those resources. The imbalance has also led to immense biodiversity loss that has caused one of the biggest threats to human survival – climate change. It has now been described as a “code red for humanity.” The campaign will continue to cover issues like air pollutionwaste managementplastic banmanual scavenging and sanitation workers and menstrual hygiene. Banega Swasth India will also be taking forward the dream of Swasth Bharat, the campaign feels that only a Swachh or clean India where toilets are used and open defecation free (ODF) status achieved as part of the Swachh Bharat Abhiyan launched by Prime Minister Narendra Modi in 2014, can eradicate diseases like diahorrea and the country can become a Swasth or healthy India.

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