The greenhouse effect is a natural process that keeps the Earth’s temperature about 60°F warmer than it would otherwise be. Human activities such as burning fossil fuels for transportation and electricity and deforestation are intensifying the greenhouse effect and causing global warming. This intense greenhouse effect may cause severe economic disruption and harm to wildlife and humans if left unabated.
The greenhouse effect refers to the process where greenhouse gases like carbon dioxide, methane, nitrous oxide, and fluorinated gases in the Earth’s atmosphere trap some of the sun’s heat, creating a natural greenhouse within the lower atmosphere. These gases allow sunlight to pass through the atmosphere, but prevent some of the sun’s energy from escaping back out to space. Most of this solar energy ends up heating the surface of the Earth, which in turn radiates infrared energy back towards the atmosphere at longer wavelengths.
Greenhouse gases in the atmosphere absorb this infrared radiation and re-radiate it in all directions, including back towards the Earth’s surface and the lower atmosphere. This retains heat somewhat like glass retains heat in a greenhouse. Without the natural greenhouse effect, the Earth’s average temperature would be about 0°F instead of the more habitable 57°F. This greenhouse effect provides a livable temperature and has remained relatively stable for thousands of years, allowing human civilization to flourish.
Since the Industrial Revolution began in the late 1700s, human activities have significantly increased the amounts of greenhouse gases in the atmosphere, especially carbon dioxide and methane. Carbon dioxide levels are now the highest they’ve been in at least 800,000 years according to ice core records. The burning of fossil fuels like coal, oil, and natural gas for electricity and transportation is the primary cause of increased CO2 emissions in the atmosphere. Deforestation, agriculture, waste disposal, and some industrial processes also contribute to increased greenhouse gases.
The increased CO2 and other greenhouse gases act just like additional blankets trapping heat, substantially intensifying the natural greenhouse effect. According to the U.S. Environmental Protection Agency, human activities have increased atmospheric CO2 levels by more than 45% since the pre-Industrial era. Measurements also show levels of methane and nitrous oxide in the atmosphere are rising largely due to human activities like animal agriculture, livestock, coal mining, and fertilizer production respectively. The accumulation of greenhouse gases in the atmosphere from human activities is enhancing the greenhouse effect and altering the climate system.
Evidence for human-caused climate change and global warming includes rising global temperatures, widespread melting of snow and ice, rising global sea levels, and other climate-related impacts. The World Meteorological Organization reported that 2020 tied with 2016 as the warmest year on record at 1.2°C above pre-industrial levels. Sixteen of the 17 warmest years in recorded history have occurred since 2001 according to the U.S. National Oceanic and Atmospheric Administration. The years from 2015 to 2020 are consecutively the warmest on record. Global temperatures are rising at least twice as fast in the Arctic.
Scientific evidence clearly shows that greenhouse gas emissions from human activities are the dominant cause of observed global warming since 1950 according to multiple independent studies. Climate models have accurately predicted the observed temperature rises when factoring in human greenhouse gas emissions and natural factors versus natural factors alone. The carbon released from burning fossil fuels cannot rapidly escape to space because the rate of fossil fuel burning vastly exceeds the rate at which natural sinks like oceans and forests can absorb it. As a result, the excess carbon stays in the lower atmosphere, enhancing the heat-trapping greenhouse effect.
If greenhouse gas emissions continue unabated according to current trajectories, the intensified greenhouse effect is expected to have widespread and severe economic and environmental impacts according to climate scientists from the Intergovernmental Panel on Climate Change. Some projected impacts of increased global warming include more frequent and intense extreme weather events like heat waves, drought, wildfires, hurricanes and flooding. Sea level rise is expected to accelerate due to melting land ice and ocean water expansion, threatening coastal cities and island nations. Climate change impacts are also likely to reduce crop yields and disrupt food production in many regions. Warming oceans will damage coral reefs and dislocate fish and marine life.
Rising temperatures and climate instability may also harm human health via more prevalent diseases, respiratory illness, disease outbreaks and mental health impacts. Large populations may face water scarcity, food shortages and instabilities that could amplify conflict and migration flows according to a report from U.S. security officials. Some low-lying areas could become uninhabitable as sea level rise escalates risks from coastal flooding. Entire ecosystems and biodiversity hotspots may be threatened by rising temperatures, more frequent wildfires, droughts and related impacts disrupting natural habitats. Unchecked climate change therefore poses serious risks to global stability and prosperity.
While some human and natural impacts may now be unavoidable due to past emissions already accumulated in the climate system, the severity and rate of future climate change impacts still depends greatly on how much and how quickly greenhouse gas emissions can be reduced globally according to climate scientists. Major emissions reductions in line with limiting global warming to well below 2°C compared to pre-industrial levels will be required to avoid the most catastrophic effects projected by climate models according to the IPCC. Transitioning to renewable energy generation like solar and wind power instead of fossil fuel combustion is essential. Improving energy efficiency, electrifying transportation, advancing carbon capture technologies and large-scale reforestation efforts can all help draw down atmospheric greenhouse gases over time. International cooperation on emissions reductions under the Paris Climate Agreement provides a framework for global action, but much faster progress is still urgently needed by scientists’ assessments.
The greenhouse effect is a natural process making the Earth habitable, but human activities since the Industrial Revolution have substantially amplified the greenhouse effect through increased emissions. Scientific evidence clearly shows that human-caused global warming poses widespread threats to societies and natural systems if left unaddressed. While some impacts are now difficult to avoid, significantly reducing greenhouse gas pollution as soon as possible in line with scientific advice remains essential to curb the intensity and harm of the intensified greenhouse effect unleashed by industrialization and deforestation over the past two centuries. International cooperation on rapidly transitioning away from fossil fuels to renewable energy could help prevent the most severe projected consequences of climate change according to climate science. Further research is continually improving our understanding of climate impacts and potential solutions to stabilize Earth’s climate.
Andrew Stroud