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Climate Change
Greenhouse Gases, Temperature & Impacts
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Climate change refers to long term shifts in temperature, precipitation, and weather patterns, while global warming is the specific rise in Earth's average surface temperature. These changes matter because they affect ecosystems, agriculture, sea level, water supplies, and human health. The main driver today is the increase in greenhouse gases from burning fossil fuels, deforestation, and industry. Understanding the science helps explain both current impacts and possible solutions.
The greenhouse effect is a natural process that keeps Earth warm enough for life, but human activity is strengthening it. Sunlight enters the atmosphere mostly as shortwave radiation, and Earth's surface absorbs part of that energy and re-emits it as infrared radiation. Greenhouse gases such as carbon dioxide, methane, and water vapor absorb and re-radiate some of this outgoing heat, which raises surface and lower atmosphere temperatures. As this energy imbalance grows, it leads to warming oceans, melting ice, shifting climate zones, and more frequent extreme weather events.
Key Facts
- Global warming is the long term increase in Earth's average surface temperature, mainly due to increased greenhouse gases.
- Incoming solar energy is mostly shortwave radiation, while Earth emits energy mainly as longwave infrared radiation.
- A simple energy balance idea is absorbed solar energy = outgoing infrared energy in a stable climate.
- Greenhouse gases absorb outgoing infrared radiation and re-radiate part of it back toward the surface.
- Carbon dioxide concentration has risen from about 280 ppm before the Industrial Revolution to over 420 ppm today.
- Radiative forcing from carbon dioxide can be approximated by DeltaF = 5.35 ln(C/C0) W/m^2.
Vocabulary
- Greenhouse effect
- The process in which gases in the atmosphere absorb and re-radiate infrared energy, warming Earth's surface and lower atmosphere.
- Carbon dioxide
- A greenhouse gas released by respiration, combustion, and industry that plays a major role in modern climate change.
- Infrared radiation
- Longwave energy emitted by Earth's surface after it absorbs sunlight.
- Albedo
- The fraction of incoming sunlight that a surface reflects back into space.
- Radiative forcing
- A measure of how a factor such as greenhouse gases changes the balance of incoming and outgoing energy in the climate system.
Common Mistakes to Avoid
- Confusing weather with climate, because a cold day or a storm does not represent the long term average patterns used to define climate. Climate is measured over many years or decades.
- Thinking the greenhouse effect is entirely bad, because the natural greenhouse effect is necessary for life on Earth. The problem is the enhanced greenhouse effect caused by extra greenhouse gases from human activity.
- Assuming ozone depletion is the main cause of global warming, because ozone loss and greenhouse warming are different environmental issues. Some gases can affect both, but rising carbon dioxide and other greenhouse gases are the main cause of current warming.
- Believing all sunlight is trapped directly by greenhouse gases, because greenhouse gases mainly absorb outgoing infrared radiation from Earth rather than most incoming visible sunlight. This distinction is central to understanding the mechanism.
Practice Questions
- 1 Use DeltaF = 5.35 ln(C/C0) to estimate the radiative forcing when carbon dioxide rises from 280 ppm to 420 ppm. Give your answer in W/m^2.
- 2 A surface receives 340 W/m^2 of incoming solar energy and reflects 30% of it. How much solar energy is absorbed by the Earth system?
- 3 Explain why melting sea ice can increase future warming even though ice itself does not produce heat.