The greenhouse effect is the process by which radiation from a planet’s atmosphere warms the planet’s surface to a temperature above what it would be without its atmosphere. This phenomenon is caused by certain gas components in the atmosphere that exhibit the greenhouse effect, which helps to regulate the planet’s temperature. The greenhouse effect is a natural process that helps maintain an average temperature of around 15°C (59°F) on Earth instead of the average temperature of around -18°C (0°F) if only incoming visible radiation was considered without accounting for an atmosphere. Human activities that increase the concentration of greenhouse gases in the atmosphere are intensifying the greenhouse effect and leading to an enhancement of the planet’s natural greenhouse effect, resulting in global climate change and global warming.
Greenhouse gases like carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and fluorinated gases effectively absorb and emit infrared radiation within the thermal infrared range. The infrared radiation that gets absorbed by these gases is radiated in all directions and much of it back towards Earth’s surface, analogous to a greenhouse. Normal atmospheric constituents like oxygen (O2) and nitrogen (N2) are poor absorbers of infrared radiation and do not contribute significantly to the natural greenhouse effect. The intensity of infrared radiation that greenhouse gases can absorb depends on their atmospheric concentration and shape. Greenhouse gases readily accept the infrared light emitted from Earth’s surface trying to escape to space and efficiently re-emit it in all directions, including back towards the surface. This greenhouse effect helps trap some of the outgoing infrared radiation emitted from Earth’s surface to warm the lower atmosphere and surface. activities like burning of fossil fuels for energy and transportation have dramatically increased the concentration of greenhouse gases like CO2 in the atmosphere from 280 parts per million to over 415 parts per million since the industrial revolution began in 1750. Deforestation has also reduced the natural ability of forests and plants to absorb excess atmospheric CO2 through photosynthesis. Large-scale livestock farming and rice cultivation produce significant amounts of methane, another potent greenhouse gas. Agricultural activities have increased atmospheric levels of nitrous oxide as well. Chlorofluorocarbons and hydrochlorofluorocarbons that were once widely used as refrigerants and in aerosol propellants are also potent greenhouse gases that are long-lived in the atmosphere. The enhanced greenhouse effect due to rapidly rising levels of greenhouse gases from human activities is trapping more outgoing infrared radiation in the lower atmosphere and warming the climate system.
The impacts of the enhanced greenhouse effect due to human-caused climate change include rising global temperatures, widespread changes in weather patterns, melting of glaciers and ice sheets, more extreme weather events, rising sea levels due to thermal expansion of oceans and melting ice sheets. Global temperatures have risen around 1°C since pre-industrial times according to scientific data and climate models indicate further warming of between 2–5°C by 2100 depending on how much greenhouse gas emissions can be mitigated going forward. The rising temperatures are intensifying the global water cycle by driving more evaporation and precipitation. Altered weather patterns are shifting rainfall zones, increasing the risks of both floods and droughts in different parts of the world.
The rapid melting of glaciers and ice sheets in places like Greenland and Antarctica from the warmer climate is contributing significantly to global sea level rise. Sea levels have risen up to 8-10 inches since 1900 and the rate of rise has accelerated since the 1990s due largely to growing ice melt from Greenland. Arctic sea ice minimum extents have declined precipitously as warmer ocean and air temperatures thin out and melt the sea ice. As warmer ocean and air temperatures accelerate ice sheet melt and thermal expansion of seawater, further sea level rise of 1 meter or more by 2100 is possible under higher emissions pathways. Higher seas imperil coastal communities and will accelerate coastal erosion and increase the frequency and severity of coastal flooding even with small rises in sea level.
The added heat energy retained by greenhouse gases in the lower atmosphere is also raising global ocean heat content and temperatures, contributing to more extreme weather like hurricanes drawing energy from warmer oceans. More precipitation extremes linked to a warming climate increase flood risks around the world. Some drought-prone regions have grown drier as well, exacerbating water security issues. Events like heat waves are predicted to be more severe and frequent. The climate changes underway redistribute rising risks to human health, infrastructure, water supplies, agricultural systems, wildlife and entire ecosystems from rising temperatures, more erratic weather, rising seas and changing rainfall patterns. Marginalized populations in developing countries face greater vulnerability to food and water insecurity from climate change impacts.
Taking urgent action to curb greenhouse gas emissions is essential to avoid the most severe consequences of climate change according to climate experts and reports from the Intergovernmental Panel on Climate Change. Transitioning to renewable energy and low-carbon transportation while protecting natural carbon sinks in forests and oceans can help limit warming below dangerous levels. Yet global greenhouse gas emissions continue rising despite agreements like the Paris Accord, jeopardizing ambitious global climate goals. While some impacts are now unavoidable due to past emissions, adaptation measures through risk management strategies, infrastructure upgrades, carbon removal technologies and nature-based solutions can help build resilience against climate change at national and local levels. Sustained global effort and cooperation on sharply reducing emissions alongside climate adaptation is critical to manage risks in the coming decades from the intensifying enhanced greenhouse effect.
The greenhouse effect is a natural process that helps regulate the Earth’s temperature and make it habitable for life. Human activities amplifying greenhouse gases in the atmosphere are speeding up the greenhouse effect and disrupting the climate balance which supported human civilization. Urgent mitigation of emissions alongside investments in adaptation are needed to avoid escalating consequences for people and natural systems from an overheated climate undergoing rapid change from the intensifying enhanced greenhouse effect due to accumulated pollution. Sustained global action remains imperative to transition societies towards renewable energy while protecting natural carbon sinks, in order to stabilize the climate and limit risks in the future from a warming world with rising greenhouse gases.
Andrew Stroud