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Fact check: Global warming caused by human activity, not solar winds or weakened magnetic field

USA TODAY logo USA TODAY 8/5/2022 Kate S. Petersen, USA TODAY
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The claim: Global warming is occurring because of solar winds and changes in Earth's magnetic field

Solar winds consist of charged particles emitted by the sun. Earth's magnetic field – generated by churning, molten iron in the planet's core – prevents most of these particles from interacting with Earth's atmosphere.

However, some social media users are sharing a post that claims solar winds and weakness in Earth's magnetic field are responsible for global warming.

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"The reason why it’s getting hotter and hotter is because our magnetic shield is weakening," reads the caption of a July 17 Facebook post. "Right now there is a huge crack in it and the more solar winds we keep getting then the more heat we get from those solar winds. Our troposphere is heating up mote (sic) and more. The Sun is waking up and is very active. So that’s why most of the Earth is burning up." 

The post garnered thousands of interactions in two weeks, but it is wrong.

Solar winds do not heat the troposphere – the lower section of Earth's atmosphere where humans reside, according to researchers. While the intensity of both Earth's magnetic field and the sun can fluctuate, neither can account for Earth's recent warming trend. 

Modern global warming is not naturally occurring. After investigating many alternative explanations, researchers have concluded that warming is caused by human-emitted greenhouse gases trapping excess heat on the Earth.

USA TODAY reached out to the Facebook user who shared the post.

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Solar winds do not cause global warming

Due to Earth's magnetic field, most charged particles from solar winds never interact with Earth's atmosphere. However, when conditions are right, they can be funneled into the upper atmosphere at Earth's poles, NASA research scientist Martin Mlynczak told USA TODAY.

The resulting interactions between the particles and a layer of the upper atmosphere, called the thermosphere, create the famous northern and southern lights

But these solar winds lack the energy necessary to heat the lower atmosphere where global warming is occurring, Mlynczak said in an email.

Energy from solar winds primarily gets dispersed in the thermosphere and is then lost to space, he said.  The lower atmosphere, or troposphere, is too dense and already contains too much thermal energy for solar winds to make a difference. 

"The energy contained in the solar wind is utterly insignificant," Mlynczak said. "Suggesting that the solar wind could heat the troposphere is tantamount to warming the head of pin and plunging it into a large swimming pool and expecting that all the water in the pool will evaporate."

Rather than solar wind, it is sunlight, or solar radiation, that effectively warms the troposphere, Rona Oran, a computational space physicist at Massachusetts Institute of Technology, told USA TODAY.

"Solar radiation carries a million times the amount of energy carried by (solar wind)" and is "indifferent to the magnetic field," passing right through it, she said in an email. 

Fact check: NASA says modern climate change caused by human activity, not solar orbital cycles

Global warming is happening because of radiation trapped by greenhouse gases

Rather than being caused by solar winds, global warming occurs through a multi-step process that begins when this solar radiation strikes and warms Earth's surface. When the Earth warms, it releases radiation of its own.

When this radiation strikes greenhouse gases in the lower atmosphere, the gases also release radiation. Some of this radiation is emitted back down toward Earth, further heating the planet, while some of it escapes into space.

But through satellite monitoring, researchers have observed that more radiation is entering Earth than leaving it, said Mlynczak.

This imbalance is one of many pieces of evidence that global warming is caused by an increase in human-emitted atmospheric greenhouse gases and not by some external force.

"While it may be tempting to look for other causes of surface warming, such as solar wind or magnetic field effects, these have been considered and discounted by scientists for some time now," Mlynczak said. 

Fact check: Short term global temperature fluctuations do not negate climate science, overall warming

Global warming cannot be explained by magnetic field weakening or solar changes

The post is correct that Earth's magnetic field has weakened. 

Its strength has diminished by roughly nine percent in the last 200 years, according to Zoë Thomas, a climate researcher at the University of South Wales, told USA TODAY. 

However, this is considered a normal amount of change.

"The magnetic field periodically undergoes periods of time when it is stronger or weaker, and this (current) weakening is well within what is considered the normal level of fluctuations," she said in an email. "This does not have an impact on global temperatures."

Despite the post's claim that the sun is "waking up," changes in the sun's behavior cannot explain modern global warming.

"The amount of solar energy that Earth receives has followed the Sun’s natural 11-year cycle of small ups and downs with no net increase since the 1950s," says NASA's Global Climate Change website. But "over the same period, global temperature has risen markedly. It is therefore extremely unlikely that the Sun has caused the observed global temperature warming trend over the past half-century."

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Our rating: False

Based on our research, we rate FALSE the claim that global warming is occurring because of solar winds and changes in Earth's magnetic field. Global warming is caused by thermal radiation that has been trapped by greenhouse gases. Solar winds don't warm the lower atmosphere. Scientists have studied changes in the sun and the Earth's magnetic field and determined neither plays a role in global warming.

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This article originally appeared on USA TODAY: Fact check: Global warming caused by human activity, not solar winds or weakened magnetic field

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