Climate Change – Its stages and causes

From the beginning, there have been many instances of climate change on the planet earth. These instances prove that the changes in the climate are natural and happen continuously. 

• The changes in the interglacial and glacial period can be witnessed in the geological records
• At high latitudes and altitudes, the evidence of the proceeding and retreating of the glaciers can be monitored by studying their geomorphological features
• Glacial lakes contain sediments that showcase the existence of cold and warm periods
• The tree rings showcase the existence of dry and wet periods
• During the 8000 B.C. there was a cold and wet climate at the place where Rajasthan desert stands today

Stages of Climate Change

• Earth experiences various stages of climate change over a period. According to the geological past, earth witnessed a warm climate during the Silurian, Cambrian, and Ordovician periods. This period can be traced way back to 300 to 500 million years ago
• The interglacial and glacial time spans were during the time of Pleistocene Epoch. The final major peak of the glacial period happened some 18,000 years ago
• The ongoing interglacial period started approximately ten thousand years ago

Causes of Climate Change 

The causes of climate change can be categorised into terrestrial  causes and astronomical causes. 

Astronomical Causes:

Astronomical Causes reflect in the transformation in the solar output and are related to the sunspot activities. 

Sunspot Activities:

The cool and dark patches on the surface of the sun increase or reduce in a cyclical way. These activities are referred to as sunspot activities. 

As per some meteorologists, storms, cool, and wet climates tend to occur with the increase in the sunspots. However, a decrease in the same results in a dry and warm climate. 

Milankovitch Oscillations:

Milankovitch Oscillations refers to the infer cycles in the characteristics associated with earth’s orbit around the sun and the altercations in the earth’s axial tilt due to its wobbling. These factors change the insolation amount coming out from the sun which may further change in the climate. 

Terrestrial Causes 

Volcanic Eruptions:

Volcanic eruptions result in the release of numerous aerosols that stay in the earth’s atmosphere for a long time. They reduce the radiation of the sun that reaches the earth’s surface. For instance, the El Cion and Pinatubo eruptions that occurred recently result in the lowering of the earth’s temperature for some period. 

Anthropogenic Effect:

The concentration of gases emitted by the greenhouses in the earth’s atmosphere is increasing. This trend is known as anthropogenic effect. 

Effects of 19th Century Climate Changes 

• The climate exhibits variations irrespective of time and place. However, the 19th century witnessed extreme climate changing events. Some of the worst floods and hottest temperatures were recorded in this century
• The Sahel region witnessed a devastating drought from 1967 to 1977. It is located to the Sahara Desert’s south and can be considered as one such variation
• The impact of climate changes can be studied through events like migration of people, bumper crop yields or devastating crop failures, floods, etc
• Europe has gone through periods of wet, cold, dry, and warm climates. The 10th and 11th centuries witnessed dry and warm conditions that forced the Vikings to settle down in Greenland
• The period between 1550 to 1850 is considered to be a little ice age in Europe
• The global temperatures soared from 1885 to 1940. This rate of temperature rise slowed down gradually after the 1940s

Global Warming 

• The earth’s atmosphere is showing the symptoms of a greenhouse because of the tremendous release of greenhouse gases in it
• The atmosphere begins to absorb the substantial part of long wave radiations that are released upwards by the surface of the earth. The gases that are capable of absorbing these radiations are known as greenhouse gases
• This results in warming of the earth’s atmosphere which is generally referred to as the global warming due to greenhouse effect 

GHGs (Greenhouse Gases)

• Ozone (03), Carbon dioxide (CO2), Methane(CH4), Nitrous Oxide (N2O), and Chlorofluorocarbons (CFCs) are the primary greenhouse gases
• Gases like carbon monoxide (CO) and nitrous oxide (NO) tend to react with GHGs and influence their concentration

The impact of a GHG molecule varies according to these factors:

1. The magnitude of the improvement in concentration. 
2. The period of its existence.
3. The wavelength of the radiation which it is capable of absorbing.

• Among the GHGs, carbon dioxide has the highest concentration in the atmosphere
• Carbon dioxide gets released due to the combustion of coal, gas, oil, and other fossil fuels
• Forests absorb CO2 for their growth. Therefore, deforestation and other factors contributing to the variations in the land use leads to a higher concentration of CO2
• The time taken by the earth’ atmosphere to revive from the modifications brought about by a GHG molecule depends on the time during which it sustains in it
• CFCs are released due to human activities and are highly effective as well
• When present in the lower troposphere, ozone is capable of absorbing terrestrial radiation. It also absorbs the ultraviolet radiation radiated by the sun
• Ozone is present in the stratosphere in which the UV rays convert oxygen into the ozone gas
• When the ozone layers become thin or get depleted, it is called the ozone hole. Antarctica witnesses some of the biggest depletion of the ozone

Conclusion

In order to plan for the future, we must first understand how the environment is changing. Climate science allows us to predict how much rain will fall next winter and how much sea levels will rise significantly as of rising sea temperatures.