What Factors Determine Earth’s Climate? A01235523

climate
1. The atmospheric component of the climate system most obviously characterises climate; climate is often defined as ‘average weather’. Climate is usually described in terms of the mean and variability of temperature, precipitation and wind over a period of time, ranging from months to millions of years (the classical period is 30 years)
radiaton
1. Solar radiation powers the climate system.
  1. There are three fundamental ways to change the radiation balance of the Earth:
    1. 1)By changing the incoming solar radiation (e.g., by changes in Earth’s orbit or in the Sun itself)
    2. 2)By changing the fraction of solar radiation that is reflected (called ‘albedo’; e.g., by changes in cloud cover, atmospheric particles or vegetation)
    3. 3)By altering the longwave radiation from Earth back towards space (e.g., by changing greenhouse gas concentrations
Reflectives sistem on Earth
1. The amount of energy reaching the top of Earth’s atmosphere each second on a surface area of one square metre facing the Sun during daytime is about 1,370 Watts
  1. About 30% of the sunlight that reaches the top of the atmosphere is reflected back to space. Roughly two-thirds of this reflectivity is due to clouds and small particles in the atmosphere known as ‘aerosols’.
    1. Light-coloured areas of Earth’s surface – mainly snow, ice and deserts – reflect the remaining one-third of the sunlight. The most dramatic change in aerosol-produced reflectivity comes when major volcanic eruptions eject material very high into the atmosphere.
      1. Rain typically clears aerosols out of the atmosphere in a week or two, but when material from a violent volcanic eruption is projected far above the highest cloud, these aerosols typically influence the climate for about a year or two before falling into the troposphere and being carried to the surface by precipitation.
        Major volcanic eruptions can thus cause a drop in mean global surface temperature of about half a degree celsius that can last for months or even years. Some man-made aerosols also significantly reflect sunlight.
Why te Earths surfaces is so warm?
1. The reason the Earth’s surface is this warm is the presence of greenhouse gases, which act as a partial blanket for the longwave radiation coming from the surface.
  1. 1. The greenhouse effect
      1. The most important greenhouse gases are water vapour and carbon dioxide.
      2. The two most abundant constituents of the atmosphere – nitrogen and oxygen – have no such effect.
      3. Clouds, on the other hand, do exert a blanketing effect similar to that of the greenhouse gases; however, this effect is offset by their reflectivity, such that on average, clouds tend to have a cooling effect on climate (although locally one can feel the warming effect: cloudy nights tend to remain warmer than clear nights because the clouds radiate longwave energy back down to the surface).
      4. Human activities intensify the blanketing effect through the release of greenhouse gases. For instance, the amount of carbon dioxide in the atmosphere has increased by about 35% in the industrial era, and this increase is known to be due to human activities, primarily the combustion of fossil fuels and removal of forests.
    2. Atmospheric circulation
      1. Because the Earth is a sphere, more solar energy arrives for a given surface area in the tropics than at higher latitudes, where sunlight strikes the atmosphere at a lower angle
      2. Atmospheric circulation is primarily driven by the release of this latent heat. Atmospheric circulation in turn drives much of the ocean circulation through the action of winds on the surface waters of the ocean, and through changes in the ocean’s surface temperature and salinity through precipitation and evaporation.
      3. Due to the rotation of the Earth, the atmospheric circulation patterns tend to be more east-west than north-south. Embedded in the mid-latitude westerly winds are large-scale weather systems that act to transport heat toward the poles. These weather systems are the familiar migrating low- and high-pressure systems and their associated cold and warm fronts.
"Ice-albedo feedback"
1. As rising concentrations of greenhouse gases warm Earth’s climate, snow and ice begin to melt.
  1. This melting reveals darker land and water surfaces that were beneath the snow and ice, and these darker surfaces absorb more of the Sun’s heat, causing more warming, which causes more melting, and so on, in a self-reinforcing cycle.

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What Factors Determine Earth’s Climate? A01235523

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