It can be a surprise, given the vast body of evidence that binds people together climate change, directly observed evidence of human impact on the climate had still avoided science. I mean so far.
In a single study, NASA calculated the individual forces of recent climate change through direct satellite observations. And in line with decades-old climate models, greenhouse gases and airborne pollution particles called aerosols from burning fossil fuels are responsible for the lion’s share of modern heating.
In other words, NASA has proven what determines climate change through direct observations – a gold standard in scientific research.
“I think most people would be surprised that we haven’t closed this small gap in our long list of evidence supporting anthropogens yet. [human-caused] climate change, “said Brian Soden, co-author of the study and a professor of atmospheric science at the Rosenstiel School of Marine and Atmospheric Sciences at the University of Miami.
So far it is known that fast heating of the last century is not natural. Rather, it is the result of the accumulation of greenhouse gases that capture heat, such as carbon dioxide (CO2) and methane, much of it burning fossil fuels.
The science behind why the Earth is warming
When sunlight enters the atmosphere, some of it is reflected back into space without warming the Earth. The rest is absorbed by the Earth’s surface and atmosphere and re-radiated as heat. Some of this heat escapes back into space, but the rest of the heat is trapped by specific molecules such as CO2, methane and water vapor. Simply put, the more greenhouse gases the atmosphere has, the more heat it captures and the higher the temperature.
GODMOTHER
Since the mid-1800s, CO2 in the atmosphere it has risen from 280 parts per million to 415 parts per million – a 50% increase – and is now the largest in the last 3 million years. Carbon dioxide in the atmosphere is growing at a rate 100 times faster than it should be naturally.
At the same time, suspended pollution particles, called aerosols, cool the atmosphere by blocking sunlight. This unintended side effect of the Industrial Revolution proved useful in masking a greenhouse heating.
While these particles have been effective in counteracting some of global warming from the middle to the end of the twentieth century, their impact is declining as pollution has gradually been clarified since the 1980s. Although this is great health news, it reveals additional heating in the system.
Together, the change in heat absorbed in our atmosphere due to changes in greenhouse gases and aerosols is called “radiative forcing”. These changes in radiative forcing throw the Earth’s energy balance. This is because, for the average temperatures of the Earth to remain constant, the “energy input” from the sun must be equalized by the “energy output” from the Earth into space.
When these numbers are equal, the Earth maintains its balance. But when greenhouse gases accumulate, the energy that comes out is less than the energy that enters the Earth’s system, which heats our oceans and atmosphere, creating an imbalance in the Earth’s energy budget.
What NASA has done in this study is to calculate or quantify the individual forces measured from specialized satellite observations to determine how much each component heats or cools the atmosphere. To everyone’s surprise, what they discovered is that the radiative forces, which computer models have shown for decades, were warming the Earth, match the changes they measure in observations.
A new perspective from NASA
Gavin Schmidt, director of the NASA Goddard Institute for Space Studies, says that science has long had an overwhelming amount of indirect evidence of the factors that warm the Earth. The predicted energy imbalance, illustrated by decades of computer models, has become apparent to all mankind, from disappearing glaciers to more extreme weather disasters to ocean warming.
“We have had good evidence for a long time that the estimated energy imbalance was real due to the rising ocean heat content. This is a very strong confirmation that the models predicted warming for the right reasons,” explains Schmidt. He says scientists have also had direct evidence that changes in greenhouse gases affect heat transfer and absorption in the atmosphere, but only in localized environments, not a comprehensive assessment.
Soden adds that science has strong observational evidence that CO2 has increased in the last century due to greenhouse gas burns and that laboratory measurements confirm that CO2 absorbs heat, which theoretically should cause the planet to warm at about the rate observed in the last century. However, Soden says that observing heat capture from space is actually quite difficult. This new research solves this challenge.
“This is the first calculation of the total radiative forcing of the Earth using global observations, taking into account the effects of aerosols and greenhouse gases,” said Ryan Kramer, lead author and researcher at NASA’s Goddard Space Flight Center in Greenbelt. Maryland. “There is direct evidence that human activities are causing changes in the Earth’s energy budget.”
Specifically, this study was able to calculate solid numbers for heat changes trapped in the Earth system from individual contributors influencing heat transfer, such as radiation, clouds, and water vapor, for the period 2003-2019. The researchers did this by analyzing satellite observations and applying what they call “radiative nuclei” to unleash the various components that control the transfer, absorption and emission of heat inside the Earth’s system and what is sent back into space. So far, satellite observations of the Earth’s radiation budget have measured only the total amount of radiation changes, not the individual components.
Then there are also feedbacks on the climate system, which represent a smaller but still significant amount of heating. An example of this is that as the atmosphere heats up, it can hold more water vapor and this means that it can catch more heat, further allowing more water vapor to accumulate. This is a positive feedback that perpetuates the warming.
The result: From 2003 to 2018, radiative forcing increased by 0.5 watts per square meter (W / m2), which explains the planetary imbalance, the excess heat trapped in the Earth’s system. The researchers concluded that this increase was indeed due to a combination of mainly increasing concentrations of greenhouse gases and, to a lesser extent, recent reductions in aerosol emissions.
For reference, Schmidt says the excess of 0.5 W / m2 added to the Earth system from 2003-2018 is roughly equivalent to one Christmas tree bulb for every 5 square meters of area on Earth. It may not seem like much, but one would expect a lot of energy to heat the planet by more than half a degree Fahrenheit in just 16 years. In other words, 0.5 W / m2 of excess heat absorbed by the Earth’s system is 10 times the total energy used by humans in a year, which means everything from cooking stoves to nuclear energy.
“In reality, the observational results came just as the theory predicted,” says Soden. “There is no surprise in the results, but rather it is rather” scoring the i’s and passing the t’s “on anthropogenic [human-caused] climate change. Closes the last link between rising CO2 levels and global warming. “
But this study does more than just provide concrete evidence of the connection between humans and recent climate change. It also illustrates how far science has come in discovering the secrets that govern the functioning of our physical universe.