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Climate Forcing’s

  • Climate “forcings” are factors in the climate system that either increase or decrease the climate system's effects.
  • Positive forcings such as excess greenhouse gases warm the earth while negative forcings, such as the effects of most aerosols and volcanic eruptions, actually cool the earth.
  • Atmospheric aerosols include volcanic dust, soot from fossil fuels' combustion, particles from burning forests and mineral dust.
  • Dark carbon-rich particles such as soot from diesel engines absorb sunlight and warm the atmosphere.
  • Conversely, exhaust from high-sulphur coal or oil produce light aerosols that reflect sunlight back to space, producing a cooling effect. Aerosols that form naturally during volcanic eruptions cool the atmosphere. Large volcanic eruptions can eject enough ash into the atmosphere to lower temperature for a year or more until the atmosphere's sulfate particles settle out.

(a) Forcing

  • Altering the Energy Balance
    (i) The power of a process to alter the climate is estimated by its “radiative forcing,” the change in the Earth’s energy balance due to that process.
    (ii) Some climate forcings are positive, causing globally averaged warming, and some are negative, causing cooling. Some, such as from increased CO2 concentration, are well known; others, such as aerosols, are uncertain.
  • Natural Forcings
    (i) Natural forcings include changes in the amount of energy emitted by the Sun, prolonged variations in Earth’s orbit, and volcanic eruptions.
    (ii) Since the start of the industrial revolution, the only natural forcing with any long-term significance has been a small increase in solar energy reaching Earth. However, this change is not nearly enough to account for the current warming.
  • Human-Induced Forcings
  • Human activities can also cause climate forcing. These activities include greenhouse gas and aerosol emissions from burning fossil fuels and the land surface modifications, such as deforestation.
  • Human-Generated Greenhouse Gases
  • Greenhouse gases are a positive climate forcing; that is, they have a warming effect. Carbon dioxide emitted from fossil fuel burning is presently the largest single climate forcing agent, accounting for more than half of the total positive forcing since 1750.
  • Human-Generated Aerosols
    (i) Burning fossil fuels adds aerosols to the atmosphere. Aerosols are tiny particles in the atmosphere composed of many things, including water, ice, ash, mineral dust, or acidic droplets.
    (ii) Aerosols can deflect the Sun’s energy and impact the formation and lifetime of clouds. Aerosols are a negative forcing; that is, they have a cooling effect.
  • Causes of Climate Change
  • While natural forcings do exist, they are not significant enough to explain the recent global warming. Human activities are very likely responsible for most of the recent warming.

How to estimate the effect of each gas?

Each gas’s effect on climate change depends on three main factors:

  • How much of these gases are in the atmosphere?
    (i) Concentration, or abundance, is the amount of a particular gas in the air. Greenhouse gas concentrations are measured in parts per million, parts per billion, and even parts per trillion.
    (ii) One part per million is equivalent to one drop of water diluted into about 13 galloons of liquid (roughly the fuel tank of a compact car).
  • How long do they stay in the atmosphere?
    (i) Each of these gases can remain in the atmosphere for different amounts of time, ranging from a few years to thousands of years.
    (ii) All of these gases remain in the atmosphere long enough to become well mixed, meaning that the amount that is measured in the atmosphere is roughly the same all over the world, regardless of the source of the emissions.
  • How strongly do they impact global temperatures?
    (i) Some gases are more effective than others at making the planet warmer and “thickening the Earth’s blanket (greenhouse gas)”.
    (ii) For each greenhouse gases, a Global Warming Potential (GWP) has been calculated to reflect how long it remains in the atmosphere, on average, and how strongly it absorbs energy.

Global Warming Potential

  • Global warming potential describes the impact of each gas on global warming.
  • The two most important characteristics of a GHG in terms of climate impact are how well the gas absorbs energy (preventing it from immediately escaping to space), and how long the gas stays in the atmosphere.
  • The Global Warming Potential (GWP) for a gas is a measure of the total energy that a gas absorbs over a particular period of time (usually 100 years), compared to carbon dioxide.
  • Gases with a higher GWP absorb more energy, per pound, than gases with a lower GWP, thus contributing more to warming Earth.

 GWP & Lifetime of Green House Gases

Carbon dioxide (CO2) has a GWP of 1 and serves as a baseline for other GWP values.

  • The larger the GW P, the more warming the gas causes. For example, methane’s 100-year GWP is 21, which means that methane will cause 21 times as much warming as an equivalent mass of carbon dioxide over a 100-year time period.
  • Methane (CH4) has a GWP more than 20 times higher than CO2 for a 100-year time scale. CH4 emitted today lasts for only 12 years in the atmosphere, on average. However, on a pound-for-pound basis, CH4 absorbs more energy than CO2, making its GWP higher.
  • Nitrous Oxide (N2O) has a GWP 310 times that of CO2 for a 100-year timescale. N2O emitted today remains in the atmosphere for an average of 120 years.
  • Chloro fluoro carbons (CFCs), hydro fluoro carbons (HFCs), hydro chloro fluoro carbons (HCFCs), perfluoro carbons (PFCs), and sulfur hexafluoride (SF6) are called high-GWP gases because, for a given amount of mass, they trap substantially more heat than CO2.

Receding Glaciers-A Symptom of Global Climate Change

150 years ago there were 147 glaciers in Glacier National park, but today only 37 glaciers remain, and scientists predict that they are likely to melt by the year 2030. Similarly, glaciers all across the Himalayas and Alps are retreating and disappearing every year. There are almost 160,000 glaciers found in Polar Regions and high mountain environments. Therefore, researchers are increasingly using satellite remote sensors to routinely survey our world’s glaciers in a fraction of the time.

(i) Impact of glacial retreat

  • The retreat of glaciers in the Andes and the Himalayas will have a potential impact on water supplies.
  • Climate change may cause variations in temperature and snowfall, causing changes in the mass balance of a glacier.
  • The Himalayas and other mountain chains of central Asia support large regions that are glaciated. These glaciers provide critical water supplies to dry countries such as Mongolia, western China, Pakistan and Afghanistan. The loss of these glaciers would have a tremendous impact on the ecosystem of the region.
  • World’s leading scientists predict that global warming may pose serious threat to national and global economy and the environment.
  • The poor and low-lying countries will find it difficult to cope with the damages caused by changing climate and rise in sea level
The document Climate Change- 2 | Environment for UPSC CSE is a part of the UPSC Course Environment for UPSC CSE.
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FAQs on Climate Change- 2 - Environment for UPSC CSE

1. What is climate forcing and how does it contribute to climate change?
Ans. Climate forcing refers to the factors or mechanisms that can alter the Earth's energy balance and cause changes in the climate system. These forcings can be both natural, such as volcanic eruptions and variations in solar radiation, and anthropogenic, like greenhouse gas emissions. Climate forcing plays a significant role in climate change as it can either warm or cool the planet by modifying the amount of energy that enters or exits the Earth's atmosphere.
2. How do greenhouse gases act as climate forcings?
Ans. Greenhouse gases, such as carbon dioxide (CO2) and methane (CH4), act as climate forcings by trapping heat radiated from the Earth's surface and preventing it from escaping into space. This phenomenon, known as the greenhouse effect, leads to an increase in the average global temperature. The rising concentrations of greenhouse gases in the atmosphere, primarily due to human activities like burning fossil fuels and deforestation, enhance this effect and contribute to global warming.
3. Are there any natural climate forcings apart from greenhouse gases?
Ans. Yes, apart from greenhouse gases, there are several natural climate forcings that can drive climate change. These include volcanic eruptions, which release large amounts of ash and aerosols into the atmosphere, blocking sunlight and causing temporary cooling. Additionally, variations in solar radiation due to changes in the Earth's orbit and solar activity can also act as natural climate forcings, influencing long-term climate patterns.
4. How do aerosols act as climate forcings and what are their sources?
Ans. Aerosols are tiny solid or liquid particles suspended in the atmosphere. They can act as climate forcings by either scattering or absorbing solar radiation, thereby influencing the amount of energy reaching the Earth's surface and affecting climate. The sources of aerosols are diverse and include natural sources like dust storms and volcanic emissions, as well as human activities such as industrial processes and the burning of fossil fuels.
5. Can climate forcings be mitigated to address climate change?
Ans. Yes, climate forcings can be mitigated to address climate change. Efforts to reduce greenhouse gas emissions, such as transitioning to renewable energy sources and improving energy efficiency, can help mitigate the warming effect of these forcings. Additionally, measures to reduce other climate forcings, such as controlling the release of aerosols and limiting deforestation, can also contribute to addressing climate change. It is important to implement a combination of adaptation and mitigation strategies to effectively tackle the complex issue of climate change.
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