Which Answer Best Describes The Greenhouse Effect?

What is the greenhouse effect?

The greenhouse effect is a natural process that warms the Earth’s surface. When sunlight reaches the Earth’s atmosphere, some of it is reflected back to space while the rest is absorbed and re-radiated by greenhouse gases. Greenhouse gases include water vapor, carbon dioxide, methane, nitrous oxide, and ozone. These gases trap heat in the atmosphere, preventing it from escaping into space. This greenhouse effect is what makes the Earth habitable by keeping temperatures warm enough to support life.

The greenhouse effect becomes enhanced when the concentrations of greenhouse gases rise due to human activities like burning fossil fuels. This causes more heat to be trapped, increasing the Earth’s average surface temperatures. The natural greenhouse effect warms the Earth to about 59°F (15°C) on average. But human activities have increased greenhouse gas levels so much that the enhanced greenhouse effect is warming the planet above pre-industrial levels, causing global warming and climate change.

What causes the greenhouse effect?

The greenhouse effect is caused by certain gases in Earth’s atmosphere that trap heat. The main greenhouse gases are:

  • Carbon dioxide (CO2)
  • Methane
  • Nitrous oxide
  • Water vapor

While greenhouse gases occur naturally and help keep Earth warm enough for life, human activities since the Industrial Revolution have increased the amounts of these gases in the atmosphere. Burning fossil fuels like coal, oil and natural gas releases large amounts of CO2. Clearing forests also releases CO2. Livestock such as cows and sheep produce methane. Fertilizers contain nitrous oxide.

Increasing greenhouse gas levels causes a positive feedback loop. More heat is trapped, which causes more water vapor to evaporate. Since water vapor is a powerful greenhouse gas, this further enhances the greenhouse effect. This loop amplifies the initial warming caused by human greenhouse gas emissions.

How does the greenhouse effect warm the Earth?

The greenhouse effect warms the Earth’s surface and climate system due to the way greenhouse gases like carbon dioxide, methane, and water vapor interact with infrared radiation from the Sun. Here’s how it works:

The Earth receives visible light from the Sun, which passes through the atmosphere and warms the surface. The Earth then emits this energy back into the atmosphere as infrared radiation. Greenhouse gases in the atmosphere absorb a significant portion of this infrared radiation before it can escape into space.

These greenhouse gases then re-radiate the absorbed infrared radiation in all directions. Some of this re-emitted radiation is directed back toward the Earth’s surface, effectively trapping the heat and causing additional warming. The more greenhouse gases in the atmosphere, the more infrared radiation gets absorbed and re-emitted, amplifying the greenhouse effect.

As a result of this process, the temperature at the Earth’s surface increases. The greenhouse effect creates a natural blanketing effect, allowing the Earth to be warm enough to support life as we know it. But human activities like burning fossil fuels have enhanced this effect, leading to excess warming of the climate system.

Evidence of the Enhanced Greenhouse Effect

There are several clear signs that the greenhouse effect has been enhanced by human activities:

Rising Global Temperatures
Global surface temperatures have increased by about 1.8°F since 1880. The last five years have been the warmest on record, with 2016 being the warmest year so far. This warming trend cannot be explained by natural causes alone.

Melting Glaciers and Sea Ice
Glaciers all over the world have been retreating rapidly, and the amount of Arctic sea ice in summer has declined by 40% since the late 1970s. This melting ice leads to sea level rise.

Sea Level Rise

Global sea levels have risen by about 8 inches since 1880, and the rate has accelerated in recent decades. Rising seas increase coastal flooding and erosion.

Ocean Acidification

About 30% of human-caused CO2 emissions have been absorbed by the oceans, making them more acidic. Ocean acidity has increased by about 30% since the Industrial Revolution, impacting marine ecosystems.

Impacts of the enhanced greenhouse effect

The enhanced greenhouse effect is already having profound impacts on the planet’s climate and human society. The most significant impact is climate change. Global temperatures have risen approximately 1.1°C since the late 1800s, causing widespread melting of snow and ice, and rising sea levels. The past decade was the warmest on record.

The warming climate is also linked to an increase in the frequency and intensity of some extreme weather events. Heatwaves are more common, wildfires are larger and last longer. Heavy precipitation events are increasing, raising the risk of flooding. Tropical cyclones are generating higher rainfall amounts.

Climate zones are also shifting as regions warm. Plant and animal species are migrating towards the poles or to higher elevations. Some sensitive species may go extinct if they cannot adapt quickly enough to the changing climate.

The changing climate is negatively impacting human health as well. Heat stress has led to more heat-related illnesses and deaths. Poor air quality resulting from wildfires has increased respiratory and cardiovascular hospitalizations. The geographic range of insects that transmit diseases like malaria and dengue fever is expanding, exposing more people to these illnesses.

Positive feedback loops

One concerning aspect of global warming is that it can set into motion positive feedback loops that amplify the greenhouse effect. There are a few major feedback loops that climate scientists are monitoring closely:

As global temperatures rise, ice sheets and glaciers melt at increasing rates. This melting exposes more land and open ocean, which have a much lower albedo (reflectivity) than ice and snow. More of the sun’s radiation is absorbed rather than reflected, causing further warming.

Warmer temperatures also lead to more evaporation from the oceans and land. Water vapor is a powerful greenhouse gas that traps heat, so increasing humidity leads to further atmospheric warming.

Finally, higher temperatures are beginning to thaw permafrost regions in the Arctic. This releases previously trapped carbon dioxide and methane – two major greenhouse gases that were locked away in frozen soils. The release of these gases due to melting permafrost creates more warming.

These are concerning positive feedbacks that act to amplify human-caused climate change. They have the potential to accelerate warming beyond what climate models currently project.

How to mitigate the greenhouse effect

There are several ways we can take action to reduce the impacts of the enhanced greenhouse effect. The most direct approach is to reduce burning of fossil fuels like coal, oil and natural gas. These release large amounts of carbon dioxide when burned, which builds up in the atmosphere and traps more heat. Phasing out fossil fuel use in favor of renewable energy sources like solar, wind and hydro power can significantly cut greenhouse gas emissions.

Reforestation and afforestation efforts can also help mitigate climate change. Planting more trees removes carbon dioxide from the air through photosynthesis. While forests can’t offset all human emissions, expanding forests worldwide can make a measurable dent in atmospheric carbon levels.

Emerging carbon capture technologies may also play a role. These systems filter out carbon dioxide from power plant and industrial emissions before they enter the atmosphere. The carbon can then be stored underground or repurposed into fuels and materials. While costs are still high, carbon capture may grow as an emissions reduction strategy.

Transitioning to a low-carbon economy will require large systemic changes, from how we produce energy to how we use land. But concrete steps like increasing renewable power, restoring forests and developing carbon capture can put us on the path toward mitigating the greenhouse effect.

International agreements

Governments around the world have recognized the threats posed by climate change and have sought to address the problem through international agreements. Three major agreements stand out:

UN Framework Convention on Climate Change

The UN Framework Convention on Climate Change (UNFCCC) was adopted in 1992 and entered into force in 1994. It provided a framework for international cooperation to combat climate change but set no binding limits on greenhouse gas emissions. The UNFCCC has near universal membership, with 197 countries having ratified it.

Kyoto Protocol

The Kyoto Protocol was adopted in 1997 and operationalized in 2005. It represented the first time binding greenhouse gas emission reduction targets were agreed to by developed countries. 37 industrialized countries committed to reduce emissions by an average of 5 percent below 1990 levels between 2008-2012. The United States notably did not ratify the Kyoto Protocol.

Paris Agreement

In 2015, the Paris Agreement was adopted and opened for signatures. It represented a new, comprehensive climate change agreement building on previous efforts. The Paris Agreement’s central aim is to keep global temperature rise well below 2 degrees Celsius and pursue efforts to limit increase to 1.5 degrees Celsius. Over 190 countries have joined. Developed countries agreed to take the lead by undertaking absolute economy-wide reduction targets while developing countries would continue enhancing mitigation efforts. The Agreement also included provisions on adaptation and climate finance mechanisms.

Public perceptions

There is a wide range of public perceptions regarding climate change and the enhanced greenhouse effect. Surveys show that most people agree climate change is happening, but there is less consensus on the primary causes. Many believe human activities like burning fossil fuels are the main drivers, while others think natural climate cycles play a bigger role. There are also differences in the level of concern about climate change impacts. People living in coastal regions tend to be more worried about sea level rise, for example.

Support for policies to mitigate climate change also varies. Policies like carbon pricing or clean energy incentives tend to receive broad public support according to polls. However, support often depends on the specific costs and benefits to individuals. People want climate action but may oppose policies that significantly increase energy prices or restrict industries providing jobs in their communities. Bridging this gap between general concern and support for concrete policy steps remains a challenge.

In summary, views on climate change are nuanced. While most agree it is occurring, perceptions on causation, impacts and appropriate responses are more mixed. Public education and clear communication of the scientific consensus could help build wider support for solutions.

Looking forward

As greenhouse gas emissions continue to rise, climate models project significant warming in the coming decades. Under a high-emissions scenario, global temperatures could rise 4°C or more by 2100. This level of warming would have devastating consequences such as sea level rise, increases in extreme weather, and loss of ecosystems.

To avoid the worst impacts of climate change, the international community has agreed on the goal of limiting global warming to well below 2°C, preferably 1.5°C, compared to pre-industrial levels. This requires rapid and deep reductions in greenhouse gas emissions globally. Most climate scientists agree net-zero CO2 emissions must be achieved by around 2050.

Reaching these ambitious targets will require a massive shift away from fossil fuels and a rapid transition to renewable energy sources like solar, wind and geothermal. Other solutions include electrifying transportation, improving energy efficiency in buildings and industry, reducing deforestation, and developing technologies to remove CO2 from the atmosphere. Individuals can help by reducing energy use, switching to green power, eating less meat, and pressuring governments and corporations to enact climate policies.

While the challenge is daunting, innovations in clean tech and changes in consumer habits and social attitudes give hope. With immediate and concerted global action, the worst climate impacts can still be avoided. The coming decades will be crucial in determining the future habitability of our planet.

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