Greenhouse gas

**Greenhouse Gas Properties:**
– Greenhouse gases trap heat from sunlight on Earth’s surface.
– Important greenhouse gases include carbon dioxide, water vapor, and methane.
– Greenhouse gases absorb radiation emitted by the Earth, causing the greenhouse effect.
– Without greenhouse gases, Earth’s average surface temperature would be -18°C.
– Most abundant greenhouse gases in Earth’s atmosphere are water vapor, carbon dioxide, methane, nitrous oxide, and ozone.

**Sources of Greenhouse Gases:**
– Carbon dioxide is the primary driver of global warming.
– Methane contributes significantly to warming and lasts around 12 years in the atmosphere.
– Human activities since the Industrial Revolution have significantly increased methane and carbon dioxide levels.
– Majority of carbon dioxide emissions come from fossil fuel combustion.
– Methane emissions originate from agriculture, fossil fuel production, and waste.

**Impact of Greenhouse Gases:**
– Average global surface temperature has risen by over 1.2°C since the pre-industrial period.
– Continued emission rates may lead to a temperature rise exceeding 2.0°C by 2040-2070.
– United Nations IPCC considers a 2.0°C rise as dangerous.
– Greenhouse gases cause the Earth’s surface to radiate heat back into the atmosphere.
– Greenhouse gases absorb and emit infrared radiation.

**Atmospheric Properties:**
– Greenhouse gases absorb and emit infrared radiation in the same wavelength range as Earth’s emissions.
– Nitrogen and oxygen make up 99% of Earth’s dry atmosphere and are not affected by infrared radiation.
– Trace gases like carbon dioxide, methane, and nitrous oxide account for less than 0.1% of the atmosphere but contribute to the greenhouse effect.
– Argon is monatomic and transparent to thermal radiation.
– Greenhouse gases’ asymmetry in charge distribution allows them to interact with electromagnetic radiation.

**Radiative Forcing:**
– Water vapor absorbs over a broad range of wavelengths.
– Earth’s surface temperature depends on the balance between incoming and outgoing energy.
– Greenhouse gases affect Earth’s energy balance by trapping heat.
– Carbon dioxide and water vapor play significant roles in Earth’s energy absorption.
– Greenhouse gases like methane and nitrous oxide contribute to radiative forcing.