Global Warming Causes

By Irina Bright.

This article is part of our Environment section

See the complete list of all our Pollution Articles here.

What are the main global warming causes? While there are several natural causes that may influence the temperature of our planet, a vast majority of climate scientists attribute the recently observed global warming phenomenon mostly to human activities. A 2007 climate change report released by the global climate authority IPCC re-affirms in no uncertain terms that “there is very high confidence that the net effect of human activities since 1750 has been one of warming” (Ref. 1).


industrial global warming Industry-Dependent Earth
Photo: Steven Allen

Fundamental Causes of Global Warming

Natural Causes of Global Warming

Important Anthropogenic Greenhouse Gases

Economic Sectors Acting as Global Warming Causes

Global Emissions of Greenhouse Gases

     Energy Sector Emissions
     Land Use Emissions
     Industrial Processes Emissions
     Waste Management Emissions

Case Study: Deforestation




Fundamental Global Warming Causes

It is no surprise that global warming is a result of human-induced pollution.

As we have seen before, there are many types of environmental pollution and specifically air pollutants, which negatively affect the health of the environment but do not directly contribute to global warming.

Instead, the main immediate global warming cause is the increased concentration of greenhouse gases in the atmosphere.

The greenhouse gases are the by-products of many human activities.

Once emitted, some of these greenhouse gases end up in the atmosphere, where they trap a certain amount of solar energy (which would have otherwise escaped to space), and thus radiate this energy back to the Earth raising the planet’s average temperature.

So, the FIRST fundamental global warming cause is an absolute dependence of the modern human society on the burning of fossil fuels, which is the most important source of greenhouse gas emissions.

The focal point of this cause is the generation of Energy for use both in industry and commercial/private sector.

Fossil fuel combustion is especially heavily used as a source of energy for industry.

In fact, industry literally cannot exist without fossil fuels.

Carbon dioxide (CO2) is the main greenhouse gas emitted as a by-product of fossil fuel combustion. This gas is the most important immediate global warming cause. Some amounts of carbon dioxide are removed from the atmosphere by the carbon sinks, such as tropical rainforests and oceans, as part of the process of carbon exchange between the atmosphere and the Earth (“carbon cycle”). This carbon exchange has been taking place for thousands of years. It is an implicit guarantor of the Earth’s climate stability since the amount of carbon on the planet is more or less constant.

Carbon is indeed “the chemical basis of all known life” (Ref. 2). The carbon content of past living organisms has been stored in the form of fossil fuels – oil, gas and coal (ref. 3), which we use in virtually every aspect of our lives.

But the problem is that, as Barry Commoner notes, (ref. 4): “The amounts of these fuels burned to provide society with energy represent the carbon captured by photosynthesis over millions of years. So, by burning them…we have returned carbon dioxide to the atmosphere thousands of times faster than the rate at which it was removed by the early tropical forests.”

In other words, we now release very large amounts of carbon dioxide at a very high rate, and the nature is unable to remove it in good time. This leads to the accumulation of extra carbon in the atmosphere and, consequently, to global warming.

So the first global warming cause is related to activities which are performed to generate energy for industry and commercial & private sector needs.

The SECOND fundamental global warming cause is related to the way we use our land, i.e. Land Use.

Among other applications, most common land use activities include:

  • Modern agricultural practices employed to breed animals, grow cereals, fruits & vegetables and other foods, all for human consumption. The two important greenhouse gases emitted by agricultural practices are methane (CH4) and nitrous oxide (N20).
  • Clearance of land for timber sales or for the expansion of human settlements / cattle ranches. Alongside a cocktail of pollution released as part of this process, the main greenhouse gas emitted is carbon dioxide (CO2). A very important element of this area is tropical deforestation, especially by way of forest fires, which alongside other pollutants causes the release of carbon dioxide.

Natural Global Warming Causes

The following natural factors may cause an increase in the Earth’s temperature: (Ref. 5)

Changes in solar energy output

Since the sun is the only source of energy for the functioning of the Earth’s climate system, any changes in solar output may lead to climate change and, specifically global warming.

It is predicted that a change in solar output by only 1% per century may change the average temperature of the planet by between 0.5 to 1.0°C.

Changes in the Earth’s orbital characteristics

Changes in the shape of the Earth’s orbit around the sun as well as the tilt of the Earth’s axis alter the total amount of solar energy received by the planet. This would also affect the planet’s temperature.

Summary of Important Anthropogenic Greenhouse Gases

global warming pollution Global Warming Pollution

So, among the most important anthropogenic greenhouse gases we have:

  • Carbon dioxide (CO2)
  • Methane (CO4)
  • Nitrous Oxide (N2O)
  • Fluorocarbons (incl. hydrofluorocarbons (HFCs) and perfluorocarbons (PFCs))
  • Sulfur hexafluoride (SF6)

Many of these gases come from natural sources.

But it is the human-caused contribution of these gases to global warming that we are interested in for the purposes of our discussion.

We will focus on three greenhouse gases – carbon dioxide, methane and nitrous oxide – since they are the main anthropogenic contributors to global warming.

Carbon dioxide is by far the most important past and current greenhouse gas, followed by methane and nitrous oxide.

According to the calculations of the potential impact of each greenhouse gas on the future global temperatures weighed by their global warming potential Global warming potential (GWP) is a measure of how much a given mass of greenhouse gas is estimated to contribute to global warming. It is a relative scale which compares the gas in question to that of the same mass of carbon dioxide (whose GWP is 1 by definition). A GWP is calculated over a specific time interval and the value of this must be stated whenever a GWP is quoted or else the value is meaningless. (Wikipedia) and based on the year 2000 emissions data, the contribution of each gas to the total temperature rise over the next 100 years is projected to be: (Ref. 6)

  • carbon dioxide – 72%
  • methane – 19%
  • nitrous oxide – 9%

Although some non-greenhouse air pollutants do not directly contribute to global warming, once in the air they may be transformed into actual greenhouse gases (for example, carbon monoxide (CO) may be transformed into carbon dioxide (CO2) ) and thus indirectly contribute to climate warming.

Such non-greenhouse gases are called precursor gases.

Some of the most important precursor gases are carbon monoxide (CO), nitrogen oxides (NOx) and volatile organic compounds (VOC).

Major Economic Sectors Acting as Global Warming Causes

As we described above, Energy and Land Use activities are the major anthropogenic sources of greenhouse gas emissions. They are complemented by Industrial Processes and Waste Management.

The pie chart below shows the shares of each sector in the total amount of global greenhouse gas emissions (weighed by their global warming potential).

greenhouse effect

The energy sector is by far the largest emitter of greenhouse gases (70%) followed by the land use sector (23%), waste management (4%) and industrial processes (3%).

Below we analyse exactly which sub-sectors within each sector are the biggest emitters of certain greenhouse gases.

Global emissions of greenhouse gases (weighed by their global warming potential) based on the year 2000 emissions data (EDGAR), in teragram (Tg) (Ref. 7)

Energy Sector



CH4 (CO2eq)

N2O (CO2eq)


% of total

Power Generation

8,814 3 30 8,847 31%

Industrial Sector
(excl. refineries etc)

4,398 8 9 4,415 15%


4,276 22 32 4,329 15%

Residential, Commercial, and Other Sector

3,390 42 7 3,439 12%

Other Transformation Sector
(incl. refineries etc)

2,222 9 5 2,236 8%

Gas Production & Transportation

0 1,235 0 1,235 4%

Non-Energy Use and Chem. Feedstocks
(CO2 only)

916 0 0 916 3%

Coal Production

0 849 0 849 3%


654 0 6 660 2%

Oil Extraction, Transportation and Handling

291 262 0 554 2%

Intl. Shipping

428 0 1 429 1%

Rail and other non-road

390 0 1 390 1%

Biofuel Residential

0 345 0 345 1%


25,778 2,774 90 28,642 100%

As we can see, power generation is the biggest source of greenhouse gases (specifically, CO2) within the energy sector, with 31% of the energy sector’s total emissions.

Power generation includes public electricity and heat production, according to the UNFCCC emissions reporting guidelines. (Ref. 8)

A very significant proportion of power plants around the world depends on fossil fuels (coal, natural gas, oil) as their sources of energy.

And as we know, fossil fuel combustion is the primary global source of carbon dioxide, the most powerful of all greenhouse gases acting as global warming causes.

Coal is a particularly dirty fuel. It is not only a source of greenhouse gases including methane. It is also a source of other waste products such as heavy metals (including arsenic, lead, mercury etc) polluting the environment and resulting in radioactive waste. (Ref. 9) Many countries heavily depend on coal for power generation. For example, in 2006 coal was used to produce roughly 49% of total electricity capacity of the US. (Ref. 10) Developing countries such as Russia are especially dependent on coal as this resource is still in plentiful supply.

In addition to coal, natural gas- and oil- based power plants are also serious sources of greenhouse gases.

Industrial sector generates around 15% of the energy sector’s total emissions and includes fossil fuel combustion to power primarily manufacturing industries such as iron & steel, chemical, paper production and other industries.

Road transport is, of course, another major generator of greenhouse emissions (15% of the total amount), as still a vast majority of road vehicles around the world are currently powered by liquid oil.

Together these three sub-sectors – power generation, industrial sector and road transport – produce slightly more than 60% of the total greenhouse gas emissions related to the energy sector. Theforefore, they act as major global warming causes.

The biggest greenhouse gas emitted by the energy sector in general is, without doubt, carbon dioxide – it makes up 90% of all the greenhouse gas emissions.

Land Use Sector






% of total

Deforestation, incl. Tropical Forest Fires

2,740 243 28 3,012 31%

Animals, Enteric Fermentation

0 2,001 0 2,001 21%

Rice Cultivation

0 984 0 984 10%

Arable Land, Fertilizer Use

0 0 822 822 9%

Animal Waste Deposited to Soil

0 0 796 796 8%

Leaching & Run-off

0 0 573 573 6%

Crop Production

0 0 467 467 5%

Animal Waste Management

0 212 166 378 4%

Savannah and Shrubs Fires

0 233 41 274 3%

Deforestation, Post-Burning Effects

0 0 181 181 2%

Atmospheric Deposition

0 0 115 115 1%


2,740 3,671 3,189 9,601 100%

As for the land use sector, deforestation, animal enteric fermentation and rice cultivation are the top 3 sub-sectors with the largest greenhouse gas emissions.

Deforestation causes 31% of the total land use emissions and is a very serious problem not only from the point of view of global warming but also in respect of irreversible plant and animal diversity loss with negative consequences for many different groups of people and the planet as a whole.

Since forests are one of the largest storages of carbon, deforestation particularly through forest fires is a major source of carbon dioxide emissions globally.

This is especially true for many tropical countries which are host to tropical rainforests and all the natural resources coming with them.

Read more about deforestation in the case study below.

Enteric fermentation by farm animals (such as cattle, sheep, goats etc) is another important source of greenhouse emissions (21% of total land use emissions).

Enteric fermentation is a process through which animals produce methane in their digestive tract and then either belch it or pass it out as gas. (Ref. 11) It is one of the reasons why there are now global calls to start abandoning meat-based diets in favour of vegetarian ones.

Rice cultivation is one more major cause of methane emissions, producing 10% of total land use emissions.

There are several sub-sectors within the land use sector which emit significant amounts of nitrous oxide. This is specifically true because of a widespread use of artificial fertilizers in agricultural production.

The main greenhouse gases emitted by land use activities are methane and nitrous oxide, with a significant amount of carbon dioxide produced as a result of deforestation.

Industrial Processes






% of total

Building Materials

826 0 0 826 79%


0 0 196 196 19%

Iron & Steel

0 21 0 21 2%

Solvent Use

0 0 7 7 1%


826 21 202 1,049 100%

For industrial processes, the most important sub-sector is building materials. It includes production of cement which generates a big share of the total global anthropogenic carbon dioxide emissions.

Waste Management Sector






% of total

Human Wastewater Disposal

0 736 0 736 48%


0 577 0 577 38%

Waste Water Treatment

0 135 85 219 14%


0 1,448 85 1,532 100%

The main gas emitted by the waste management sector is methane.

Case Study: Deforestation as One of the Major Global Warming Causes

There is no doubt that over the last several decades Deforestation has become one of the greatest sources of greenhouse gas emissions and, therefore, one of the most important contributors to global warming.

Read more about different causes of rainforest destruction leading to deforestation here.

As we have seen from the figures above, deforestation accounts for at least 7% of the total global greenhouse gas emissions (though many sources often refer to a figure of 20% here - that depends on particular methodology applied to derive this figure), with the main gas being carbon dioxide plus smaller amounts of methane and nitrous dioxide.

Tropical rainforests play a very important role in regulating global and regional climate patterns.

So their destruction inevitably causes disruptions in many environmental services as well.

An extremely important service provided by the rainforests is the removal of carbon dioxide from the atmosphere by photosynthesis. In other words, it acts as a pollution / carbon dioxide sink and storage.

So in global warming terms, deforestation leads to: (Ref. 12)

  • release of carbon dioxide from the trees back into the atmosphere
  • release of carbon stores held in the soil into the atmosphere
  • destruction of forests as carbon sinks for future carbon dioxide removal (i.e. damage to the planet’s future “carbon-sequestration” potential), and
  • all of the above will further contribute to the global warming effect

However, the global warming effect from deforestation may be counterbalanced by the Earth’s increased albedo ratio. The higher albedo ratio means that the Earth will be able to reflect more solar energy back into space and thus contribute to global cooling.

The issue of deforestation has recently received a special international attention for several different reasons:

  • Deforestation is a source of greenhouse gas emissions and therefore global warming.
  • Environmental services provided by the rainforests benefit all the inhabitants of the planet rather than just citizens of the rainforest host countries.
  • It is very difficult to control deforestation on a local level.
  • The vast majority of Earth’s remaining forest cover is located in developing countries in the regions around the equator. These countries desperately need resources provided by the rainforests for their own economic and social development.

The challenge to the international community is to find sustainable ways of rainforest management which would guarantee economic development for host countries as well as rainforests’ healthy functioning.

Conclusion - Are We Ready to Change the Way We Live?

To summarize it all, greenhouse gas emissions are the immediate global warming causes. And such emissions are produced by virtually every imaginable human activity.

So it is clear, that in order to eliminate the global warming causes we need to drastically cut our greenhouse gas emissions.

And for that we need to start changing our lifestyles to make them more economical and appreciative of the environmental health, and of course start developing new, renewable sources of energy.

There are probably a couple of “latent” global warming causes which we can attend to almost immediately if we really want to:

  • Our own lifestyles and a lack of desire to change them. For example, simple things like saving electricity at home, switching to more efficient technologies, or recycling can make a real difference.
  • Absence of political will to implement required changes. Unfortunately, ubiquitous presence of vested interests (especially those of oil companies) prevents political leaders from driving the real change that we need forward.

It’s interesting to note that though global warming has been known to be a problem since the 1980s, we did not make much progress in the direction of cutting greenhouse gas emissions.

Ironically, by 2005 we actually witnessed an increase in global GHG emissions as compared to the Kyoto Protocol’s base year of 1990. (Ref. 13)

Of course, it is no easy task to reverse the process of global warming.

But it surely does not mean that we should not at least try.

Written by:     Irina Bright
Original publication Date:     2008
Republication date:     2020


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6. Author’s own calculations based on the data provided by Netherlands Environmental Assessment Agency, Project EDGAR (Emission Database for Global Atmospheric Research):

Netherlands Environmental Assessment Agency (August 16, 2005). Emissions Databases for Major Greenhouse Gases. Retrieved May 30, 2008 from

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8. United Nations Framework Convention on Climate Change (UNFCCC) (February 16, 200). UNFCCC Guidelines on Reporting and Review. Common Reporting Format for the provision of inventory information by Annex I Parties to the UNFCCC,p. 26. Published for Conference of the Parties in Bonn, Germany, 25 October – 5 November 1999

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13. The Intergovernmental Panel on Climate Change (2007). Climate Change 2007: Synthesis Report. Summary for Policymakers, p. 5. Approved in detail at IPCC Plenary XXVII in Valencia, Spain, 12-17 November 2007