Still, 43 percent of Americans said they worry about global warming a "great deal" and 20 percent said they worry a "fair amount."
When looking at political divides, the difference in the level of concern is striking. Among Democrats, 73 percent believe the effects of global warming have already begun and 87 percent believe global warming is caused by human activities. Republicans are far more skeptical, with only 41 percent believing the effects have started and 40 percent saying humans have caused global warming.
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Since last year, such skepticism among Republicans has increased, with 69 percent saying they think the seriousness of global warming is exaggerated, compared with 66 percent last year. On the other hand, only 4 percent of Democrats see the threat as exaggerated, a significant decrease from 10 percent in 2017.
As with many other issues, American views "have increasingly become politically polarized," Gallup wrote in a media release. The global consulting company suggested that the election of President Donald Trump has spurred the growing political divide when it comes to global warming.
"President Donald Trump, who has called global warming a 'hoax,' may have contributed to this widening divide by reversing a number of government actions to address the issue," Gallup wrote. "These included the announcement that the U.S. will withdraw from the 2015 Paris climate accord, the removal of climate change from the list of top U.S. national security threats and the elimination of the terms 'global warming' and 'climate change' from U.S. government websites and lexicons."
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While Americans' concern for climate change may be divided along political lines, the vast majority of scientists are concerned about the threat. A major 2013 peer-reviewed study showed that more than 97 percent of climate scientists agree on global warming. Additionally, the study showed that more than 97 percent of scientific articles find that global warming is real and largely caused by humans.
Another study published in 2016 backed-up the previous findings, concluded that the 97 percent estimate is accurate.
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In December, a major scientific study suggested that the worst-case predictions regarding the effects of global warming are most likely to be true.
Similar dire predictions led more than 15,000 scientists from around the world to sign an open letter warning that quick and drastic actions should be undertaken by society to address the threat of climate change.
The open letter, which was released last year, argued that "soon it will be too late to shift course away from our failing trajectory." Scientists warned that "time is running out" for humanity to address the crisis.
Whether or not Americans believe climate change will have an impact within their lifetime, experts suggest it is already affecting the environment, and conditions will worsen in the coming decades. Some experts researching environmental issues and their effects on global societies have suggested that climate change is a major factor behind the global refugee crisis.
A recent study by the World Bank also predicted that more than 143 million people will be displaced by 2050 in just three developing regions of the world, forced to move within their countries to escape climate-related issues.
Although mass migration may not currently be affecting most Americans' lives, it is already making an impact on U.S. foreign policy and changing how Washington acts globally.
Read the full poll data at Gallup.com.