Monday, March 24, 2014

Is the global climate changing? fingerprint variables and effects

 Climate change refers to  long - term changes in the earth's weather, including changes in temperature, wind patterns and rainfall, especially the increase in the temperature of the earth's atmosphere that is caused by the increase of particular gases, especially carbon dioxide. Global climate is determined by the energy transfer from the sun at and near the earth’s surface. This energy transfer is influenced by dynamic processes such as cloud cover and the earth’s rotation and static conditions such as the position of mountain ranges and oceans. The biosphere is primarily responsible for modulating the climate and the environment of the earth to its benefit.  The earth’s climate has warmed by approximately 0.60C over the past 100 years. The small changes in the average temperature can lead to large shifts in climate and weather. Climate change may be due to natural internal processes or external forcings, or to persistent anthropogenic changes in the composition of the atmosphere or in land use. Climate change is shown in the melting of ice-sheets and snow, warming of oceans and rising in sea levels.

Factors influencing the earth’s climate

  • Variations in the solar radiations
  • Changes in the greenhouse gas concentrations 
  • Changes in ocean circulation

    Fingerprint variables  of climate change

Fingerprints are changes that show a certain pattern that is unique to a specific climate-change driver. Finger printing assumes that each individual influence on climate has a unique signature in climate records. Fingerprint method compares the pattern of temperature trends calculated from greenhouse models with the pattern observed in the atmosphere. The climate fingerprints are estimated with computer models.

Fingerprint variables

The amount of water vapour in the atmosphere is the human fingerprint. The primary driver of atmospheric moistening is the increase in carbon dioxide caused by the burning of fossil fuels (coal, oil and natural gas).
Global mean surface temperature is a fingerprint variable used to predict enhanced greenhouse effect.
Tropopause height is an integrated fingerprint variable of human induced climate change. It reflects global scale changes in the temperature structure of the atmosphere. The Tropopause is the boundary between the turbulently mixed troposphere and the more stable stratosphere. It lies roughly 10 miles above the earth’s surface at the equator and 5 miles above the poles. The location of the tropopause is sensitive to changes in vertical profiles of atmospheric temperature. Human-induced changes in ozone and GHGs are the primary drivers of changes in the height of the tropopause.  
The heat penetration into the ocean is another fingerprint variable of climate change. The six oceans that circle the globe have been warming as a result of enhanced greenhouse warming. The heat penetration with depth varies from ocean to ocean which indicates of anthropogenic influence of climate change.

Evidences of climate change (IPCC report 2007)

The ocean temperature has risen about 0.50C in the last 40 years. The Arctic freshwater ice sheet has melted around an area of 20000 km2 from 1965 to 1995. In the last 100 years, the global average sea level risen about 10 to 25 cm. The earth experienced 11 warmest of the last 12 years. In the past 100 years, the global surface temperature has risen about 0.70C and average annual temperature in the Arctic to 10C. According to the IPCC report the main characteristic of climate change is an increase in average global temperature.

Biological effects of climate change

Climate directly affects the functions of individual organisms (e.g., growth, behaviour), modifies populations (e.g., age structure and size). Climate change also affects ecosystem structure and function (e.g., decomposition, nutrient cycling, water flows, species composition and species interaction) and the distribution of ecosystems within landscape. Warming of climate could force species to migrate to higher latitudes or higher elevations where temperatures are more conducive to their survival. 

Ecological effects of climate change

The ecological impacts of climate change are diverse altering plant phenology and growth, carbon and nutrient cycling, as well as biodiversity and extinction risk. Climate changes cause food web disruptions in the polar bears and mismatches in the timing of migration, breeding and food availability. A warming of the ocean results in acidification and mass mortality of coral reefs (Schneider et al., 2007). Increased global temperature will cause more heat waves, heavy rainstorms and frequent wildfires. Climate change has complex effects on water supply and demand. Warmer temperatures cause more precipitation, higher evaporation rates and long-lasting droughts in some places.

Human health effects of climate change

Warmer climates cause more illnesses and injury from heat waves and fires and more food- and water- borne diseases. Climate change may affect allergies and respiratory health. Warmer temperatures from climate change will increase the frequency of unhealthy levels of ground- level ozone which can damage lung tissue, reduce lung function and inflame airways. Change in climate may enhance the spread of some diseases.

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