Thegreenhouse effectis a process by whichthermal radiationfrom a planetary surface is absorbed by atmosphericgreenhouse gases, and is re-radiated in all directions. Since part of this re-radiation is back towards the surface and the lower atmosphere, it results in an elevation of the average surface temperature above what it would be in the absence of the gases.

Solar radiation at the frequencies ofvisible lightlargely passes through the atmosphere to warm the planetary surface, which then emits this energy at the lower frequencies ofinfraredthermal radiation. Infrared radiation is absorbed by greenhouse gases, which in turn re-radiate much of the energy to the surface and lower atmosphere. The mechanism is named after the effect of solar radiation passing through glass and warming agreenhouse, but the way it retains heat is fundamentally different as a greenhouse works by reducing airflow, isolating the warm air inside the structure so that heat is not lost byconvection.

If an ideal thermally conductiveblackbodywere the same distance from the Sun as the Earth is, it would have a temperature of about 5.3°C. However, since the Earth reflects about 30% of the incoming sunlight, this idealized planet'seffective temperature(the temperature of a blackbody that would emit the same amount of radiation) would be about −18°C.The surface temperature of this hypothetical planet is 33°C below Earth's actual surface temperature of approximately 14°C.The mechanism that produces this difference between the actual surface temperature and the effective temperature is due to the atmosphere and is known as the greenhouse effect.

Earth’s natural greenhouse effect is critical to supporting life. However, human activities, primarily the burning of fossil fuels and clearing of forests, have intensified the natural greenhouse effect, causingglobal warming.

Agreenhouse gas(sometimes abbreviatedGHG) is agasin an atmosphere thatabsorbsandemitsradiation within thethermal infraredrange. This process is the fundamental cause of thegreenhouse effect.The primary greenhouse gases in theEarth's atmospherearewater vapor,carbon dioxide,methane,nitrous oxide, andozone. Without greenhouse gases, the average temperature of Earth's surface would be about 33°C colder, which is about 59°F below the present average of 14°C (57°F).

Since the beginning of theIndustrial Revolution(taken as the year 1750), theexhaust gasfrom burning offossil fuelsand extensive clearing of native forests has contributed to a 40% increase in the atmospheric concentration ofcarbon dioxide, from 280ppmin 1750 to 392.6 ppm in 2012. It has now reached 400 ppm in the northern hemisphere. This increase has occurred despite the uptake of a large portion of the emissions by various natural "sinks" involved in thecarbon cycle. Anthropogeniccarbon dioxide (CO2) emissions (i.e., emissions produced by human activities) come fromcombustionofcarbon-based fuels, principallywood,coal,oil, andnatural gas.

It has been estimated that, if greenhouse gas emissions continue at the present rate, Earth's surface temperature could exceed historical values as early as 2047, with potentially harmful effects onecosystems,biodiversityandthe livelihoods of peopleworldwide.

In theSolar System, the atmospheres ofVenus,Mars, andTitanalso contain gases that cause a greenhouse effect, though Titan's atmosphere has ananti-greenhouse effectthat reduces the warming.

Global warmingandclimate changeare terms for the observed century-scale rise in the average temperature of the Earth'sclimate systemand its related effects.

Multiple lines of scientific evidence show that the climate system is warming. Although the increase of near-surface atmospheric temperature is the measure of global warming often reported in the popular press, most of the additional energy stored in the climate system since 1970 has gone into ocean warming. The remainder has melted ice, and warmed the continents and atmosphere.Many of the observed changes since the 1950s are unprecedented over decades to millennia.

1. Reuse,Reduce,Recycle
2. Use less energy around the house- Heating/Air-Con
3. Save the World byChanging a Light Bulb
4.Ditch the Car!
5. Buying Energy-Efficient Products
6. Use Less Hot Water
7. Make a routine of turning Everything off
8.Plant a Tree
9.Get a Home Energy Audit done.
10. Encourage Others to Recycle/Get involved