The process of rising average air temperatures near the Earth’s surface during the past one to two centuries is known as global warming. Climate scientists have been collecting extensive data of numerous weather events (such as temperatures, precipitation, and storms) and associated effects on climate (such as ocean currents and the chemical makeup of the atmosphere) since the mid-twentieth century. The Intergovernmental Panel on Climate Change (IPCC) was established in 1988 by the World Meteorological Organization (WMO) and the United Nations Environment Program (UNEP) to give voice to a growing conviction within the scientific community (UNEP).  Human beings and human activities have been responsible for a worldwide average temperature increase of between 0.8 and 1.2 °C (1.4 and 2.2 °F) of global warming since preindustrial times, according to a special report published by the IPCC in 2018, and most of the warming observed in the second half of the twentieth century can be attributed to human activities.

Climate change since last glaciation

Changes in the sum of qualities that constitute climate change are referred to as global warming. Changes in precipitation patterns, winds, ocean currents, and other aspects of the Earth’s climate are all examples of climate change. A federal assessment on the implications of climate change on the future of the United States has been issued. According to recent research from the Geological Survey, climate change has been more relevant over the industrial age of the previous two centuries. The climate of the Earth has changed across different periods, from a single human life to billions of years. Significant fluctuations in the worldwide extent of glaciers and ice sheets were seen throughout the Pleistocene glacial era (about 2,600,000 to 11,700 years ago). Changes in the geometry of Earth’s orbit around the Sun drove changes in the distribution of solar radiation over the planet’s surface. According to a new study, these changes occurred across tens to hundreds of millennia. 

The most recent ice age, or glacial era, ended 21,000 years ago, and is known as the Last Glacial Maximum. Continental ice sheets stretched deep into Europe and North America’s middle latitude areas during this period. The global annual mean temperature appears to have been 4–5 degrees Celsius (7–9 degrees Fahrenheit) lower than it was in the mid-twentieth century. During the last ice age, Earth’s climate was marked by more cooling at higher latitudes and very less cooling across broad portions of the tropical waters (around the Equator). The Holocene is the term used to describe the most recent period of Earth’s history. The Holocene Epoch is an era in which humans have had a significant impact on climate. However, other scientists suggest that the Holocene ended very recently and that the Earth is now in the Anthropocene Epoc, a climatic gap that might be named the Anthropocene Epoc. Since the end of the ice age, people have had a major effect on climate throughout this time period.

Causes of Global Warming

1. The greenhouse effect

A balance of solar and terrestrial radiation keeps the Earth’s average surface temperature constant. Because the frequencies of the radiation are very high and the wavelengths are relatively short, solar radiation is sometimes referred to as “shortwave” radiation. Terrestrial radiation, on the other hand, is classified as longwave radiation due to its low frequencies and long wavelengths. The total energy of incoming solar radiation is approximately 1,366 watts per square metre each year. Approximately 30 units of incoming solar energy are reflected back to space by clouds, the atmosphere, or reflecting areas of the Earth’s surface for every 100 units of incoming solar radiation. Earth’s planetary albedo is the reflective capacity of the planet, and it does not have to remain constant throughout time. Earth must emit these same 70 units back into space to preserve thermodynamic equilibrium. Some of the infrared light emitted by the Earth’s surface is absorbed by greenhouse gases. As a result of this absorption, some of the initial 70 units are unable to reach space. The presence of greenhouse gases in the atmosphere causes the surface and lower atmosphere to warm up.

2. Radiative forcing

Solar radiation and greenhouse gases in the atmosphere may change the      temperature of the Earth’s surface and lower atmosphere. According to Dr. David Frum, “radiative forcing” might be thought of as “radiative force” or “radiative forcing.” The quantity of downward-directed radiant energy impinging on the Earth’s surface is measured by radiative forcing, which is a measure of the effect of a specific climatic component. Climate variables that contribute to the warming of the Earth’s surface are known as “positive forcing,” whereas forces that cool the Earth’s land surface are known as “negative forcing.” According to the IPCC, there is no question that human-caused greenhouse gas emissions are driving global warming. Each square metre of Earth’s surface receives around 342 watts of solar energy each year on average. This amount can be linked to a change in the Earth’s temperature. Changes in the distribution of terrestrial radiation (that is, radiation emitted by Earth) within the atmosphere can cause temperature changes at the surface. Radiative forcing has a natural cause in some situations, such as during volcanic eruptions when expelled gases and ash block some of the sun radiation reaching the surface. It has an anthropogenic, or purely human, origin in other situations. Anthropogenic increases in carbon dioxide, methane, and nitrous oxide, for example, are predicted to cause positive radiative forcing of 2.3 watts per sq metre. 

3. The influences of human activity on climate

Human activity has affected global surface temperatures through altering the radiative balance that governs the Earth on a variety of temporal and geographical scales. The most substantial and well-known anthropogenic effect is the increase in greenhouse gas concentrations in the atmosphere. Humans also have an impact on climate through altering aerosol and ozone concentrations and changing the land cover of the Earth’s surface.