Climate change: Basic Concepts

 Climate change: Basic Concepts

Climate change is a very natural phenomena and the earth’s climate has witnessed changes in its climatic characteristics throughout the geological periods. Different parts of the world have undergone drastic changes in climate and the factors (Climate forcing) are many. 

• The drifting continents are the major driving force that forced the climatic change of different parts of the world along with some other natural factors. 

• These are periodic variations of solar output, 

• volcanic eruptions,  

• earth eccentricity, 

• earth obliquity and 

• earth precession or wobble etc created climate changes on a regular basis.

The glacial and interglacial period on the Earth surface  of 10,000 years interval are subject to these earth events. 

But in this modern populous human world there are some signs of climatic variability in different parts of the world with different magnitudes which are putting considerable impacts on the pattern of agriculture and settlement and the life and economy of people. The records from the recent past warn human society for climatic change in different parts of human habitations making people vulnerable and forcing them towards danger. Severe climatic hazards in the form of heat wave, flood, drought, cyclones, inundation and flooding due to oceanic surge, desertification, global warming, drying of water bodies, acid rain, ocean acidification, shortening of mountain glaciers and ice sheets in polar region,  all are signs of global climate change. 

The immediate result is the changing scenario of food production resulting in famine and hunger with severe malnutrition, livelihood changes and economic losses causing poverty, environmental forced migration and climate refugee, extinction of species due to ecosystem modification. 

Instrument records started 100- 150 years ago. The data earlier than this was collected from tree rings (one to half yearly cycle), ice cores (long column of ice), peat bogs and ocean sediments (100- 1000 year resolution). 

• Recent Climate Forcing and climate feedbacks (Factors):

Increasing concentration of carbon dioxide in the atmosphere in the last 200 years creates an enhanced greenhouse effect (climate feedbacks) in the atmosphere, which in turn forces the global average atmospheric temperature to rise (positive climate feedbacks). Positive feedback of CO2 and other greenhouse gases on global warming put positive impacts on the positive water vapour feedback, Even melting of snow and ice and permafrost zones further lead to lowering of its albedo, thereby causing more warming and positive climate feedback by increasing methane from melting permafrost region.

Along with global warming global dimming is also observed in some places where the amount of aerosols and dust particles has increased in the atmosphere. 

The climate forcings are natural as well as human driven. 

Human driven forces are: 

i. Increasing fossil fuel burning and increased concentration of carbon dioxide, 

ii. Loss of forest covers, 

iii. Melting of ice sheets and decreasing albedo, 

iv. Concretisation of surface etc. 

Climate both at global scale, and micro scale are changing and we are now in a position of facing various adverse climatic events. Global climate change is determined by the rise of global average temperature but there is a wide spatial variation in the temperature changes. 

Some areas of the world, especially the Cool temperate region experiences high heatwaves,

the oceanic areas in the Equatorial region experience a lowering of average temperature. 

In a few areas average temperature is reducing due to decreasing solar input because of high aerosol concentration in lower atmosphere (Called global dimming).