It is now no surprise to hear that the planet is warming up very fast. The vast majority of this warming is not natural, according to more than 99% of scientists, but rather the result of greenhouse gases released by human activity, such as the burning of fossil fuels.
Yet, with all the thousands of studies on climate change and its connection to human activities, NASA researchers have only recently given direct observations of the driving force of climate change.
Since the Industrial Revolution in the mid-19th century, when man’s appetite for coal and other fossil fuels was first stirred, the concentration of CO2 in the atmosphere has skyrocketed from 280 parts per million (ppm) to more than 415 ppm today.
We know without a doubt that greenhouse gases such as CO2, methane or water vapor capture heat in the atmosphere and thus increase surface temperatures. We also know that CO2 in the atmosphere increases 100 times faster than it naturally should.
At the same time, human activity is also responsible for air pollution, such as particles that we all know are harmful to our health, as well as those of wildlife. But some of this air pollution is in the form of aerosols, which are small particles that hang in the atmosphere where it reflects incoming sunlight back into space. In other words, this type of pollution has a global cooling effect.
Aerosols are therefore a cooling force, while greenhouse gases cause heating. The difference between the energy absorbed by the atmosphere, of which greenhouse gases are a major contributing factor, and the energy emitted by space through factors such as aerosols is known as ‘radiative forcing’.
If radiation power is zero, it means that the planet’s energy system is in balance, so the atmosphere should not get hot and should not cool down either. When radiation coercion is positive, it means that the earth’s system is out of balance and getting hot.
What NASA did in its recent study is to quantify individual radiative forcing using satellite observations to determine exactly how much each component warms or cools the planet.
For decades, scientists have been developing models of climate change that predict how temperatures will change as a function of greenhouse gases in the atmosphere. It is not surprising that the new NASA study found that radiating forces match these models after combining data from NASA’s clouds and the Earth’s radiant energy system (CERES), which reflects the flow of radiation at the top of the Earth’s atmosphere. studied, with other data sources such as ocean heat measurements.
“This is the first calculation of the Earth’s total radiative forcing using global observations, taking into account the effects of aerosols and greenhouse gases,” said Ryan Kramer, first author on paper, and a researcher at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, said. , and the University of Maryland, Baltimore County. “This is direct evidence that human activity is causing changes in the earth’s energy budget.”
Another nail in the coffin
Scientists unanimously agree that human activity is the only thing that can explain the steep rise in the average world temperature on earth, which has increased by a little more than 1 ° C (2 ° Fahrenheit) since 1880. Two-thirds of global warming has occurred since 1975, at a rate of about 0.15-0.20 ° C per decade.
Although the evidence for anthropogenic global warming is overwhelming, it was actually the first study to offer direct, not indirect, evidence in favor of this warming explanation we are currently experiencing. So far, direct evidence that changes in greenhouse gases’ atmosphere’s ability to transfer heat was only available in the local environment.
According to the study, human activities between 2003 and 2018 led to an increase in radiant power on earth by approximately 0.5 Watt / square meter.
“If we set a direct record of radiation forces calculated from observations, we can evaluate how well climate models can simulate these forces,” said Gavin Schmidt, director of NASA’s Goddard Institute of Space Studies (GISS) in New York City. . “This will enable us to make more confident projections about how the climate will change in the future.”
The findings appear in the journal Geophysical research letters.