Climate change is defined as a long-term change in the average weather patterns that have come to define Earth’s local, regional and global climates, according to NASA.

Most scientists attribute the phenomenon to both natural environmental factors, such as volcanic eruptions and the sun’s output glacial melting, as well as human activity, such as burning fossil fuels and deforestation. However, the degree to which human activity impacts this change is sometimes debated — ranging from humans being the primary cause to those who believe the impacts and threat of climate change are overblown. This article explores the evidence for the impact of each of these factors on the climate change occurring today.

Explore all stances and perspectives around climate change. Are we missing a stance or perspective? Email us!

RELATED: Unpacking Media Bias on Climate Change

Stance 1: Humans are the primary cause of climate change

CORE ARGUMENT: Human activities, particularly the burning of fossil fuels and deforestation, have caused the Earth's average temperature to rise. This is due to the increase in greenhouse gas emissions, which trap heat in the Earth's atmosphere.

More arguments for this stance:

• Concentrations of the key greenhouse gasses have all increased since the Industrial Revolution due to human activities. 
• Carbon dioxide, methane, and nitrous oxide concentrations are now more abundant in the earth’s atmosphere than any time in the last 800,000 years.
• By increasing the abundance of greenhouse gasses in the atmosphere, human activities are amplifying Earth’s natural greenhouse effect.
• Human influence on climate has been the dominant cause of observed warming since the mid-20th century, while global average surface temperature warmed by 0.85°C between 1880 and 2012.
• Current warming is occurring roughly 10 times faster than the average rate of warming after past Ice Ages. Carbon dioxide from human activities is increasing about 250 times faster than it did from natural sources after the last Ice Age.
• There is a scientific consensus that the likelihood that human activities have been the dominant cause of the recent warming is over 95%.
• Subtle changes in Earth’s orbit around the Sun are responsible for the comings and goings of Ice Ages. But the warming we’ve seen in recent decades is too rapid to be linked to changes in Earth’s orbit and too large to be caused by solar activity.
• The world is now careening toward 1.5 degrees — a critical threshold that warming should remain below to avoid the risk of increased extreme drought, wildfires, floods and food shortages.
• Climate change contributes to a web of intersecting environmental injustices that afflict less privileged demographic groups more harshly, and vice versa. One example is urban heat islands. 
• Some businesses, such as fossil fuel companies, have a monetary incentive to promote climate change denial and have used their financial resources to warp the conversation around climate change. For example, ExxonMobil has played down the impact of human emissions on the climate for decades despite their internal research agreeing with the scientific consensus.

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Stance 2: Natural factors also contribute meaningfully to climate change

CORE ARGUMENT: While human activities have contributed significantly to climate change, natural factors such as volcanic eruptions, solar radiation and natural greenhouse gas emissions also play a large role.

More arguments for this stance:

• Warming greater than the global average has already been experienced in many regions and seasons, with higher average warming over land than over the ocean (high confidence)
• The energy output of the sun is not constant: it varies over time and this has an impact on our climate. 
• Volcanic gasses like sulfur dioxide can cause global cooling, while volcanic carbon dioxide, a greenhouse gas, has the potential to promote global warming.
• Humans are a part of nature. Therefore, the things that humans create are “natural.”
• The geological archive reveals that Earth’s climate has varied as long as the planet has existed, with natural cold and warm phases.
• Natural processes are always influencing the earth’s climate.

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Stance 3: The extent of human contribution is uncertain, overblown, or nonexistent

CORE ARGUMENT:  While human activities contribute to climate change, the extent of human contribution compared to natural factors is not fully known or has been overblown.

More arguments for this stance:

• The commonly cited claim that 97% of scientists agree about global warming is based on just a handful of surveys, and much of the data backing up the claim there is a scientific consensus is faulty. Many of the studies and surveys that attempt to point to consensus have issues.
• Climate Change is the result of millions of years of cycles and the earth cycles have been occuring since long before we could measure them in days, weeks, months, and years.
• The United Nations’ Intergovernmental Panel on Climate Change (IPCC) gives researchers a monetary incentive to drum up alarmist claims that overblow human impact. Alarmism over climate change is often a way to drum up media hysteria and paper over true motives, such as anti-capitalist policies.
• Although climate change models are largely well-tuned to the past climate data we are able to obtain, they also have a degree of uncertainty due to potentially important factors about which we have incomplete information; we do not have enough accurate global data for a long enough period of time to see where there are natural warming mechanisms at work.
• There is no statistical evidence that global warming is intensifying hurricanes, floods, droughts and other natural disasters, or making them more frequent. Government data does not show a trend increase in hurricanes, tornadoes, droughts and wildfires over the last 100+ years.
• Reports of record high temperatures are impacted by the location of monitoring systems, which are often located in places with high populations and infrastructure; global satellite readings often show a less alarming picture. This “urban heat island” effect is often overlooked. Factors like El Niño are also sometimes overlooked. 
• The 19th century was one of the coldest in the last 10,000 years, so a change makes sense. 
• The rise of extra greenhouse gasses fundamentally indicates more and more people are experiencing longer and better lives.
• There is uncertainty within climate change models due to an incomplete understanding of Earth’s climate systems and their interactions; natural variability in the climate system; the limitations of climate models; bias; and measurement errors from imprecise observational instruments.
• Climate change is not severe enough to warrant being a top priority of the government compared to more urgent national concerns.

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Divya Bharadwaj is a Content intern for AllSides. She has a Left bias.

Reviewed by Evan Wagner, News Editor and Bias Analyst (Lean Left), Julie Mastrine, Director of Marketing and Media Bias Ratings (Lean Right), and Henry A. Brechter, Editor-in-chief (Center).