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Evidence for Causes of Gradual Climate Changes

Grade 9
May 17, 2023

Our planet is warming. The average Earth’s average temperature by 1.5°F over the last century and is likely to increase by another 0.5 to 8.6°F over the next century. Small changes in the planet’s average temperature can cause large and potentially dangerous shifts in climate and weather.

The evidence is undeniable. Rising global temperatures have accompanied weather and climate changes in fall. As a result, rainfall in many places has changed, causing more floods, droughts, heavy rain, and frequent and severe heat waves.

The planet’s oceans and glaciers have also undergone significant changes, with oceans warming and unbecoming acidic, ice caps melting, and sea levels rising. These and other changes will almost certainly pose challenges to our society and environment as they become more pronounced in the coming decades.

Climate change is described significant change in climate measurements that lasts for an extended period change, in other words, includes substantial changes in temperature, precipitation, or wind patterns, including other effects, that take place over several decades or longer.

Climate Change


Causes of Climate Change

The Temperature of the Earth Is a Delicate Balancing Act:

The balance of energy entering defines the temperature of the Earth and leaving the planet’s system. When the Earth’s system absorbs inbound solar energy, it warms. The Earth avoids warming when the Sun’s energy is reflected into space. Earth’s absorbed energy is released back into space. Many natural and man-made factors can cause changes in the Earth’s energy balance, including:

  • Variations in the amount of sunlight that reaches Earth.
  • Variations in the reflectivity of the Earth’s atmosphere and surface.
  • Changes in the greenhouse effect, affect how much heat the Earth’s atmosphere retains.

These factors have triggered the Earth’s climate to shift numerous times.

Scientists have restored a record of Earth’s climate dating back hundreds of thousands of years (and, in some circumstances, millions or hundreds of millions of years) by analyzing ice cores, tree rings, glacier lengths, pollen remains, and ocean sediments, as well as studying changes in Earth’s orbit around the Sun.

Model showing human and Natural influence on Climate

This record demonstrates that the climate system naturally varies over a wide range of time scales. Earlier to the Industrial Revolution in the 1700s, climate changes could be described by natural causes like changes in solar energy, volcanic eruptions, and natural changes in greenhouse gas (GHG) concentrations.


On the other hand, recent climate changes cannot be explained solely by natural causes. According to research, natural causes do not account for the majority of observed warming, particularly warming since the mid-twentieth century. Instead, human activities were likely the primary cause of the warming.

Greenhouse Gases

The greenhouse effect causes heat to be maintained in the atmosphere.

When sunlight strikes the Earth’s surface, it can be reflected into space or absorbed by the planet. After absorbing some of the energy, the planet emits some of it back into the atmosphere as heat (also known as infrared radiation).

Greenhouse gases like water vapour (H2O), carbon dioxide (CO2), and methane (CH4) absorb energy, slowing or stopping heat loss to space. GHGs act as As a result, a blanket, keeping the Earth warmer than it would be otherwise. This is commonly referred to as the “greenhouse effect.”

Greenhouse effect

Greenhouse gases and Greenhouse effect 2

The Role of the Greenhouse Effect in the Past:

CO2 levels have fluctuated with glacial cycles over the last several hundred thousand years. CO2 levels were higher during warm “interglacial” periods. CO2 levels were lower during cool “glacial” periods.

Variations in the natural resources and sinks of these gases, as well as changes in greenhouse gas concentrations in the atmosphere, can be caused by heating or cooling the Earth’s surface and oceans.  These shifting concentrations are thought to have acted as a positive feedback system, increasing temperature changes caused by long-term shifts in Earth’s orbit.

Earth’s changing CO2 Concentration

Feedback Can Increase or Reduce Changes:

Climate feedback either increases or decreases the direct warming and cooling effects. They have no direct impact on the planet’s temperature. Positive feedback refers to feedback that amplifies changes. Negative feedback is feedback that counteracts changes. Changes in surface reflectivity, clouds, water vapor, and the carbon cycle are all associated with feedback.

The most significant feedback appears to be caused by water vapor. The rate of evaporation and the ability of air to hold water vapor both increase as the earth warms, raising the amount of water vapor in the air. Because water vapor is a greenhouse gas, this contributes to even more warming.

Another example of positive climate feedback is the melting of Arctic sea ice. Sea ice melts as temperatures rise. When ice melts, it exposes the underlying sea surface, which is darker and absorbs more sunlight than ice, increasing the overall amount of warming.

Some clouds produce negative feedback. Warming, for example, can increase the amount of reflectivity of these clouds, allowing more sunlight to be reflected into space and thus cooling the planet’s surface. Other types of clouds, on the other hand, provide positive feedback.

Several positive feedbacks also contribute to increased GHG concentrations. For example, as the temperature rises:

  • Natural processes that impair acted by warming, such as permafrost thawing, tend to emit more CO2.
  • The ocean emits CO2 into the atmosphere and absorbs CO2 from the atmosphere at a slower rate.
  • Various types of land surfaces may emit more methane (CH4).

These changes increase the concentrations of GHGs in the atmosphere and contribute to global warming.

Recent role of the Greenhouse Effect

Since the Industrial Revolution around 1750, human activities have significantly contributed to climate change by adding CO2 and other heat-trapping gases to the atmosphere. The greenhouse effect has been exacerbated due to these greenhouse gas emissions, causing the Earth’s surface temperature to rise. Greenhouse gas release from burning fossil fuels is the primary human activity influencing the amount and rate of climate change.

The increase in the Concentration of Greenhouse gases

The Primary Greenhouse Gases (GHGs):

Carbon dioxide (CO2), methane (CH4), nitrous oxide (N2O), and several other GHGs are among the most significant GHGs directly emitted by humans.

1. Carbon dioxide:

It is a minimal but very important element of the atmosphere. Carbon dioxide is released by natural processes like respiration and volcanic eruptions and by human activities like deforestation, changes in land usage, and burning of fossil fuels.

Since industrial development, humans have increased the concentration of atmospheric CO2 by 48%. This is the major component of climate change.

2. Methane:

It is a hydrocarbon gas produced through both the sources such natural sources and human activities, like the decomposition of waste materials in landfills, agriculture, and particularly in rice cultivation, as well as ruminant digestion process and manure management related to domestic livestock.

Methane is a more active greenhouse gas than carbon dioxide, but it is also one of the components that is much less abundant in the atmosphere.

3. Nitrous oxide:

It is a very powerful greenhouse gas emitted by various modes like methods of soil cultivation, particularly the use of commercial and organic fertilizers, burning of fossil fuels,  production of nitric acid, and burning of biomass.

Sources of Greenhouse gases

Other Greenhouse Gases:

1. Water vapour:

It is the most abundant greenhouse gas, but mainly, it acts as a feedback to the climate. When Earth For example, the thermosphere gets warm, water vapour increases. By this, the possibility of clouds and rain increases. This makes the feedback mechanism the greenhouse effect.

2. Chlorofluorocarbons (CFCs):

Synthetic compounds are used in several products but are now mainly regulated in production and release to the atmosphere by international agreements for their capacity to add to the damage of the ozone layer. This is because CFCs are too greenhouse gases.

Effect of Sun’s Energy

The amount of energy that comes to the Earth’s system is affected by changes in the Sun’s energy:

Natural changes influence climate. affecting how much solar energy reaches Earth. Changes within the sun’s and earth’s orbits are examples of these changes.

Changes in the Sun’s rays can have an impact on the amount of Sun light that reaches the Earth’s surface. The intensity of the sunlight can cause either warming (during periods of higher solar intensity) or cooling (during periods of lower solar intensity) (during periods of weaker solar intensity). The Sun goes through an 11-year cycle of small ups Sun downs in intensity, but the effect on Earth’s climate is minor.

Variations in the shape of the Earth’s orbit, as well as the tilt and position of the Earth’s axis, can all have an impact on the amount of sunlight reaching the Earth’s surface.

Measurement of Surface temperature and Sun’s energy

In the past, variations in the intensity of the sun’s rays have historically influenced Earth’s sun’s state. For example, the so-called “Little Ice Age” between the 17th and 19th centuries may have been caused in part by a period of low solar activity from 1645 to 1715, which coincided with cooler temperatures.

The term “Little Ice Age” refers to a period of slight cooling in North America, Europe, and possibly other parts of the world. Over tens to hundreds of thousands of years, changes in Earth’s orbit have significantly impacted the climate. The amount of summer sunlight in the Northern Hemisphere appears to drive the advance and retreat of ice sheets, which are affected by changes in the planet’s orbit.

Recent Role of the Sun’s Energy:

Changes in solar energy continue have an impact on the climate. However, solar output has been lower than it has been since the mid-20th century over the last 11-year solar cycle, which does not explain Earth’s recent warming.

Similarly, changes in the shape of the Earth’s orbit and the tilt and position of the Earth’s axis affect the temperature on very long timescales (tens to hundreds of thousands of years) and thus cannot explain the recent warming.

Effects of Reflectivity

Variations in reflectivity affect how much energy enters Earth’s system.

Once solar radiation reaches the Earth’s surface, it can be reflected or absorbed. The Earth’s surface and atmosphere determine the amount of sunlight reflected or absorbed. Light-colored objects and characters, such as snow and clouds, remember the most sunlight, whereas darker objects and surfaces, such as the ocean, forests, or soil, absorb more sunlight.

The amount of solar radiation reflected by an object or surface, expressed as a percentage, is described as its albedo. The Earth, For example, has an albedo of about 30%, which means that 70% of the sunlight that reaches the planet is absorbed. Sunlight absorbed warms the Earth’s land, water, and atmosphere.

Albedo effect

Aerosols also have an impact on reflectivity. Aerosols are airborne particles or liquid droplets that can absorb or reflect sunlight. Unlike greenhouse gases, the climate effects of aerosols vary depending on their composition and location of emission.

Aerosols that reflect sunlight, such as volcanic ash or sulphur emissions from coal combustion, have a cooling effect. Those that absorb sunlight, such as black carbon (a component of soot), warm the environment.

The Role of Relativity in the Past

Nature Past changes in reflectivity, such as melting sea ice, have contributed to climate change, frequently acting as feedback to other processes.

Volcanoes have had a significant impact on climate. Volcanic particles reaching the upper atmosphere can reflect enough sunlight into space to cool the planet’s surface by a few tenths of a degree for several years. These are some examples of cooling aerosols. Volcanic particles from a single eruption do not cause long-term change because they are in the atmosphere for much fewer periods than GHGs.

Recent Role of Relativity

Human changes in land use and land cover have altered the reflectivity of the Earth. Processes such as deforestation, reforestation, desertification, and urbanization frequently contribute to climate change in the areas where they occur. These effects may be significant at the regional level but are much smaller when averaged globally.

Deforestation, Urbanization

Furthermore, human activities have increased the overall number of aerosol fragments in the atmosphere. Human-generated aerosols have a net cooling effect, offsetting roughly one-third of the total warming effect caused by human greenhouse gas emissions. Reducing overall aerosol emissions may thus result in more warming. Still, targeted reductions in black carbon emissions can help to decrease global warming.

Green House Effect and Global Warming


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