Fact check: Global warming caused by human activity, not solar winds or weakened magnetic field – USA TODAY
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.
“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.
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.
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.
“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.
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.”
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.
Our fact-check sources:
- Zoë Thomas, July 20, Email exchange with USA TODAY
- Martin Mlynczak, July 25 – Aug. 2, Email exchange with USA TODAY
- Rona Oran, July 26, Email exchange with USA TODAY
- Jürgen Matzka, July 20-26, Email exchange wtih USA TODAY
- NASA Global Climate Change, accessed July 20, Causes
- NOAA Climate.gov, Apr. 12, 2012, Do solar storms cause heat waves on Earth?
- NASA Global Climate Change, Aug. 3, 2021, Earth’s Magnetosphere: Protecting Our Planet from Harmful Space Energy
- NASA Global Climate Change, Aug. 3, 2021, Flip flop: Why variations in earth’s magnetic field aren’t causing today’s climate change
- NASA Global Climate Change, accessed July 25, Is the sun causing global warming?
- NASA, accessed July 28, Earth’s magnetosphere
- NASA, accessed July 28, Global Temperature
- Canadian Space Agency, accessed Aug. 2, What are the northern lights?
- NASA, Jan. 21, 2013, Earth’s Atmospheric Layers
- NASA Global Climate Change, Sept. 6, 2019, What Is the Sun’s Role in Climate Change?
- Australia Department of Climate Change, Energy and Environment and Water, accessed July 28, Understanding climate change
- NOAA Climate.gov, Nov. 5, 2020, How do we know the build-up of carbon dioxide in the atmosphere is caused by humans?
- NASA Global Climate Change, Oct. 2, 2019, Earth’s atmosphere: A Multi-layered cake
- University Corporation for Atmospheric Research, accessed Aug. 2, The thermosphere
- NASA Global Climate Change, July 10, 2020, Graphic: Temperature vs solar activity
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