Scientists' Consensus: Pollution's Role In Global Warming

There is a strong consensus among climate scientists that global warming is occurring and that it is caused by human activity. Surveys and studies have shown that 97% of climate scientists agree that human-caused climate change is happening, with some studies placing the consensus at 100%. This consensus is based on extensive scientific evidence, including direct measurements of rising surface air and ocean temperatures, increases in global sea levels, retreating glaciers, and changes to many physical and biological systems. The human activities causing global warming include the burning of fossil fuels, cement production, and land-use changes such as deforestation, as well as emissions of greenhouse gases such as carbon dioxide, methane, and nitrous oxide. Despite this scientific consensus, public opinion polls and politicians often point to false beliefs and claims that significant debate still exists among scientists over the true cause of climate change.

Scientific consensus on climate change

There is a strong scientific consensus that global warming is caused by human activity, specifically the increase in human-produced heat-trapping gases. The consensus is that the Earth has been consistently warming since the start of the Industrial Revolution, and that this warming is mainly the result of a rapid increase in atmospheric carbon dioxide (CO2) caused by human activities.

The scientific consensus on climate change is expressed in the reports of the Intergovernmental Panel on Climate Change (IPCC), created in 1988 by the World Meteorological Organization and the United Nations Environmental Programme. The IPCC's purpose is to evaluate the state of climate science to inform policy action, primarily based on peer-reviewed and published scientific literature. The IPCC states unequivocally that the consensus of scientific opinion is that Earth's climate is being affected by human activities, specifically the increase in greenhouse gas concentrations.

The consensus is supported by the national science academies of all major industrialized countries, as well as other organizations such as the Network of African Science Academies and the International Union for Quaternary Research. The American Meteorological Society (AMS) and the American Geophysical Union (AGU) have also issued statements supporting the consensus.

Surveys of the scientific literature have found a high level of agreement among climate scientists. A 2004 analysis of 928 scientific papers on "global climate change" published between 1993 and 2003 found that 75% explicitly expressed support for or accepted the consensus, while none rejected it. A 2013 study of over 4,000 peer-reviewed papers on climate science published since 1990 found that 97% agreed that global warming is happening and is human-caused. A 2019 review of scientific papers found the consensus on the cause of climate change to be at 100%, and a 2021 study concluded that over 99% of scientific papers agree.

Despite this strong consensus, there has been a perception of disagreement or uncertainty among climate scientists, promoted by policymakers and the media. Some corporations whose revenues might be affected by controls on emissions have also alleged uncertainties in the science. However, this impression of disagreement is incorrect, and the scientific consensus is clear.

The impact of greenhouse gas emissions

The vast majority of actively publishing climate scientists – 97% – agree that humans are causing global warming and climate change through the emission of greenhouse gases. The burning of fossil fuels for electricity and transportation, as well as land use patterns, agriculture, and industrial processes, are the primary drivers of this phenomenon.

Fossil fuels, such as coal, oil, and gas, are the largest contributors to global climate change, accounting for over 75% of greenhouse gas emissions and nearly 90% of carbon dioxide emissions. The combustion of these fuels releases carbon dioxide, nitrous oxide, and methane into the atmosphere, creating a blanket of gases that traps the sun's heat and leads to global warming.

The changing climate has far-reaching consequences for both society and ecosystems. Warmer temperatures disrupt weather patterns and natural balances, posing risks to human beings and all other forms of life. It alters the habitats and interactions of species, potentially leading to fundamental transformations in current ecosystems. Additionally, the warming climate affects the water cycle, resulting in increased precipitation in some regions, while other areas experience more prolonged and intense droughts.

Greenhouse gas emissions have long-lasting impacts, and the emissions released today will continue to affect the planet and its inhabitants for years to come. Decision-makers, companies, leaders, and activists worldwide recognize the urgency of addressing climate change and mitigating the effects of greenhouse gas emissions.

The role of human activity

The vast majority of actively publishing climate scientists – 97% – agree that humans are causing global warming and climate change. This consensus is echoed by leading science organizations worldwide, including international and U.S. science academies, the United Nations Intergovernmental Panel on Climate Change, and other reputable scientific bodies.

Human activities, such as the burning of fossil fuels, oils, and gases, release carbon dioxide and other harmful greenhouse gases into the atmosphere. These gases, including methane, nitrous oxide, and chlorofluorocarbons, trap heat and lead to a rise in the Earth's average temperature, known as the greenhouse effect. Since the Industrial Revolution, human activities have significantly contributed to this effect, altering the Earth's climate and causing societal and ecological impacts.

Deforestation is another critical factor in global warming. Trees absorb carbon dioxide and release oxygen, but when they are cut down, they release CO2 back into the atmosphere. Additionally, large-scale farming of sheep, cows, and goats releases methane, another potent greenhouse gas. These human activities have led to observable consequences, such as rising sea levels, increased ocean acidification, melting ice glaciers, changes in agricultural production, and more frequent natural disasters like floods and droughts.

The evidence for global warming

Climate change is real, and there is a significant body of evidence to support the existence of global warming. The Earth's climate has changed throughout its history, but the current warming is unprecedented, occurring roughly 10 times faster than the average rate of warming after an ice age. The planet's average surface temperature has risen by about 1.8°F (1.0°C) since 1880, with most of the warming occurring in the last 40 years. The seven or 10 most recent years have been the warmest on record.

This warming is driven largely by increased carbon dioxide emissions into the atmosphere and other human activities. The key role that carbon dioxide plays in maintaining the Earth's natural greenhouse effect has been understood since the mid-1800s. Scientific evidence, including temperature data, shows that human activities, especially the burning of fossil fuels and greenhouse gas emissions, have warmed the Earth's surface and its ocean basins. The ocean has absorbed much of this increased heat, with the top 100 meters (about 328 feet) of the ocean showing warming of 0.67°F (0.33°C) since 1969.

Further evidence of global warming can be found in the melting of mountain glaciers and polar ice sheets worldwide, the decline of snow cover in the Northern Hemisphere, and the rise in mean global sea levels. The Greenland Ice Sheet, which holds about 8% of the Earth's fresh water, is melting at an accelerating rate. Data from NASA's Gravity Recovery and Climate Experiment show that Greenland lost an average of 279 billion tons of ice per year between 1993 and 2019, while Antarctica lost about 148 billion tons of ice per year. Glaciers are retreating almost everywhere, including in the Alps, Himalayas, Andes, Rockies, Alaska, and Africa.

Scientific evidence, including temperature data, ancient evidence from tree rings, ocean sediments, coral reefs, and sedimentary rocks, and modern equipment such as satellites, all point to the existence of global warming. The vast majority of actively publishing climate scientists, around 97%, agree that humans are causing global warming and climate change.

The effects of climate change

The vast majority of actively publishing climate scientists – 97% – agree that humans are causing global warming and climate change. Climate change is already affecting ecosystems and people in the United States and worldwide.

The Arctic is one of the ecosystems most vulnerable to the effects of climate change. It is warming at least twice as fast as the global average, and this warming has consequences that are felt across the globe. The melting of land ice sheets and glaciers is contributing significantly to rising sea levels. Sea levels are also rising due to thermal expansion, and the higher sea level puts coastal areas at greater risk of erosion and storm surges.

Effects of climate change can build upon one another to damage ecosystems. For example, sea level rise can cause sediment to smother corals, and warming waters can lead to coral bleaching, while stronger hurricanes can destroy reefs. Coral reef ecosystems are home to thousands of species, which rely on healthy coral reefs to survive. Oceans absorb 93% of all the heat trapped by greenhouse gases and up to 30% of all the carbon dioxide emitted from burning fossil fuels. The frequency of marine heatwaves has increased by more than a third, leading to mass die-offs of plankton and marine mammals. The elevated absorption of carbon dioxide by the ocean leads to its gradual acidification, threatening marine life that has evolved to live in a narrow pH band, such as corals, oysters, and mussels.

Climate change is also having an impact on weather systems, making events like droughts, hurricanes, and floods more intense and unpredictable. It is also extending and intensifying wildfire seasons, with human-caused climate change estimated to have already doubled the area of forest burned in recent decades. By 2050, the amount of land consumed by wildfires in Western states is projected to increase by two to six times.

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