Global Warming and Climate Change

1. Issue in brief

Global warming and climate change

Global warming has always taken place; without it, the planet would be freezing cold and uninhabitable. It is caused by sunlight, which radiates to the earth as short wave radiation, being trapped by the 'greenhouse gases' surrounding the earth. As the solar radiation reaches the earth and the atmosphere around it (the troposphere), that part of the radiation which is converted to infra-red radiation can no longer pass through these gases so freely and is locked into the atmosphere. To try to return to an equilibrium, the air heats up until the outgoing long-wave radiation (OLR) matches the incoming solar radiation. Currently, this steady state is not being reached and the planet is gradually becoming hotter - known as the Enhanced Greenhouse Effect.

Radiative forcing describes the changes brought about by the mechanism described above. A positive radiative forcing makes the earth and the atmosphere around it hotter (global warming), whilst a negative radiative forcing makes it cooler.

Greenhouse gases and aerosols

Greenhouse gases

Greenhouse gases can be split into those that are naturally occurring, and those that are produced as a result of human activity. Important greenhouse gases include carbon dioxide, ozone, methane, nitrous oxide and water vapour. Over the last thirty or so years, there has been a steady and unprecedented climb in the levels of greenhouse gases, and most people now believe that this accelerated growth is largely man-made (anthropogenic). This increase in greenhouse gases is raising the temperature of the earth and the air around it to dangerous levels. Manufacturing, power generation, farming and transport are largely blamed, and the excessive level of greenhouse gases they produce are believed to be at the root of climate change.

See a country list of Carbon Dioxide emissions per capita here


Aerosols (microscopic airborne particles or droplets) affect global warming. Some of them (such as those from erupting volcanoes) have a cooling effect. Most aerosols will scatter and absorb solar and infra red radiation in the atmosphere, and have probably had an overall negative contribution to global warming. They also affect cloud formations by increasing the numbers of fine particles that retain the droplets in warm clouds.

On the other hand, black carbon (soot), created by burning carbonaceous fuels, tend to warm the planet. The quantity of black carbon is a function of the way in which it is burnt, and recent research indicates that the smoke from household cooking stoves is particularly high in black carbon.

Feedback effects

'Positive feedbacks' involving water vapour, snow, and ice may amplify the direct response to greenhouse gas emissions by a factor of two to three. The water vapour feedback is particularly important as water vapour is a powerful greenhouse gas, and models project that global warming will raise water vapour levels in the lower atmosphere - a phenomenon that appears to be happening already, particularly in the Northern hemisphere. Water vapour concentrations are affected by temperature and pressure, which dictate how much vapour can be carried within the atmosphere. If water vapour is at an altitude where the temperature is lower than ground temperature it will inhibit outgoing radiation, causing positive forcing. As the difference in these two temperatures widens, the effect is exacerbated. Further, as the air warms, allowing more water vapour to be held, this increases the effect, and is known as positive water vapour feedback.

Snow and ice reflect sunlight very effectively. If a small warming melts snow earlier in the year, more energy will be absorbed by the ground exposed underneath it, in turn causing more warming. This is the main reason wintertime northern regions are expected to warm the most.

Clouds are closely connected with this system; although they may prevent infrared radiation from escaping, they also reflect back some of the solar radiation. As clouds form from water vapour, they release latent heat, which can be a central influence in a weather system see IPCC information on climate change.

3. Current Best Practice

HEDON Household Energy Network has created a special interest group called CarbonSIG where through this, people who are concerned and working on climate change issues are trying to create a sustainable environment that benefits those living in poverty through information, discussion and action around improved household energy.

4. Areas of Research

Cooking and greenhouse gases

Over two billion people cook using biomass, and yet more cook one coal - the majority of whom cook over three-stone fires and / or rudimentary stoves. These cooking methods lead to substantial levels of Products of Incomplete Combustion (PICs) - over one hundred of them, among which are some of the more potent greenhouse gases, including methane and Nitrous oxide . The amount of global warming attributed to each gas is known as its Global Warming Potential (GWP), which describes its potential relative to carbon dioxide. As gases break down over different periods of time, GWP changes with the time period over which the global warming is being considered - known as the Time Horizon.

Table 1 shows some of the more common greenhouse gases, modified from the IPCC working group report 2001, showing the GWP with a time horizon of 100years:

Chemical speciesFormula100-yr GWP
Carbon dioxideCO21
MethaneCH4 (ppb)23
Nitrous oxideN2O (ppb)296

Note, however, that black carbon does not appear in these tables despite its high global warming potential. For further information on black carbon see:

Effects of global warming

There is a growing consensus that, with a business-as-usual scenario, the mean global temperature will increase by between 2C and 5C before the end of this century. We are already seeing the impacts:

  • A rise in the level of the oceans - already driving island-dwellers from their homes
  • The permafrost at the ice-caps disappearing
  • More violent and unpredictable weather - hurricanes, flash floods
  • An increase in droughts and violent rains
  • Biodiversity reduction as living things fail to evolve fast enough to survive
  • Increase in disease and epidemics as disease vectors spread geographically
  • Parts of the world becoming unbearably hot, leading to mass migrations, and land and water conflicts

Just to maintain the status quo of levels of carbon dioxide and other greenhouse gases affecting our planet, we need to reduce emissions by around 70%.


Biochar is a carbonised material made from biomass which is treated to high temperatures in a zero to low oxygen environment. Biochar can be produced in certain stove types, and can even be used in a stove as fuel. Because of its recalcitrance to degradation, biochar can be used as a carbon sink, which can mitigate against global warming.

5. Organisations/People

International action

Since 1994, most countries of the world have joined an international treaty — the United Nations Framework Convention on Climate Change to consider what can be done to reduce global warming and to cope with whatever temperature increases are inevitable. The Convention on Climate Change sets an overall framework for intergovernmental efforts to tackle the challenge posed by climate change. Under the Convention, governments strive to:

  • Gather and share information on emissions, policies and best practice
  • Launch national strategies for addressing emissions and adapting to expected impacts. These include provision of financial and technological support to developing countries
  • Cooperate in preparing for adaptation to the impacts of climate change

An addition to the treaty, the Kyoto Protocol, has more powerful (and legally binding) measures. Not all countries - notably the US - have signed up to this Treaty to date.

Who does what?

Main actors at international level
  • The Conference of the Parties (COP) is the prime authority of the Convention. It is an association of all member countries (or "Parties") and usually meets annually for a period of two weeks. These sessions are attended by several thousand government delegates, observer organizations, and journalists.
  • The Subsidiary Body for Scientific and Technological Advice (SBSTA) counsels the Conference of the Parties on matters of climate, the environment, technology, and method.
  • A Subsidiary Body for Implementation (SBI) helps review how the Convention is being applied. It also deals with financial and administrative matters.

Expert groups
  • The Consultative Group of Experts (CGE) on National Communications from "non-Annex 1 Parties" helps developing countries prepare national reports on climate change issues.
  • The Least Developed Country Expert Group (LEG)advises such nations on establishing programmes for adapting to climate change.
  • The Expert Group on Technology Transfer (EGTT) encourages the sharing of technology with less-advanced nations.

Partner agencies include
  • The Global Environment Facility, which has existed since 1991 to fund projects in developing countries that will have global environmental benefits.
  • The Intergovernmental Panel on Climate Change (IPCC) provides services to the Convention; publishing comprehensive reviews every five years of the status of climate change and climate-change science, along with special reports and technical papers

HEDON Cooking and Carbon Special Interest Group

Carbon SIG is a special interest group on cooking and carbon being established to discuss all things dealing with all things to do with climate change and household energy. Its specifically aims are to connect people and organisations working on household energy and carbon emission reduction, sequestration and adaptation to climate change, to support high quality business, government and NGO networking, to foster co-ordination and collaboration leading to the creation of new knowledge and ultimately improved household energy provision and finally to support information exchange on carbon emission reduction, carbon sequestration, and climate adaptation in the household energy sector.
Carbon SIG special interest group has its own vocabulary for making the various meanings of words for climate change and household energy precise and comprehensive to people that do not have specific knowledge on this field. You can see the CarbonSIG glossary here

Climate change science

The IPCC website on climate change (http://www.grida.no/climate/ipcc_tar/wg1/index.htm) provides a very comprehensive scientific background to the current situation. It looks at evidence based on temperature of both land and sea, humidity, clouds, rainfall, snow and ice cover - and analyses the likely effects of global warming for separate geographic areas. The summary for policymakers provides an excellent overview

Carbon trading

Carbon trading - or carbon emissions trading - is a concept where companies in the industrial world can agree to offset some of their emissions by paying for those emissions to be reduced in a developing country. There is substantial argument over whether these emission reductions are 'real' or whether this mechanism allows large industrial organisations to continue to pollute by giving them a 'conscience clause' in that their payment is used to fund development in other countries. Emissions are sold by price per tonne of carbon dioxide saved. There are two distinct mechanisms:
  • Clean Development Mechanism (CDM); This is the mechanism set up under the Kyoto protocol and is more relevant for very large projects as verification is expensive and complex. In terms of stoves, there are currently obstacles to using the CDM as biomass fuel has to be shown to be 'renewable' both before and after projects have taken place. This constraint is currently under review by the COP. Kyoto carbon trading is set to start in April 2007. A detailed description of how cooking stoves relate to the CDM can be found here
  • Voluntary market: This mechanism is perhaps more appropriate for smaller projects. Companies (represented by several of our CarbonSIG members) negotiate with organisations and industries to provide funding for development projects which reduce carbon emissions. The level of monitoring and verification differ from company to company, and are also dependent on the wishes of the industry offsetting the carbon.

7. Documents and further reading

These resources have been taken from the Carbon SIG special interest group page


Last edited by Miriam Hansen .
Page last modified on Wednesday September 29, 2010 09:02:51 GMT.
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