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climate change > overview > the changing climate and a warming world

The changing climate and a warming world

Posted: 05 Mar 2009

by Amanda Chiu

�Warming of the climate system is unequivocal, as is now evident from observations of increases in global average air and ocean temperatures, widespread melting of snow and ice and rising global average sea level.� � IPCC, Fourth Assessment Report (2007).

�Unequivocal� is a very strong word, meaning clear, unambiguous, and leaving no doubt, and sends a clear message from the scientific community to the world that the science is confirmed � climate change is real, and it is already happening.

Glacier, Himalayas<br>© DEP Kumar/UNEP/Topham
Glaciers are melting in the Himalayas
� DEP Kumar/UNEP/Topham
The natural driving force behind climate change is the greenhouse effect at work in our world's climate systems. As infrared solar radiation from the sun reaches the earth, about 30 per cent of it is reflected back into space, without entering the atmosphere. Another 20 per cent is immediately absorbed into the atmosphere, and the remaining 50 per cent reaches the Earth�s surface, where much of it is absorbed and the rest reflected back towards the atmosphere and through to space. The amount of solar radiation that reaches the Earth is about equal to the amount reflected, maintaining an energy balance. Without this greenhouse effect, the environment on Earth would not be favourable to sustaining life.

This energy balance is now being altered by two components of the atmosphere. First, greenhouse gases (GHGs) - the most well-known being carbon dioxide (CO2), methane (CH4), nitrous oxides (N2O), sulphur hexafluoride (SF6), hydrofluorocarbons (HFCs), and perfluorocarbons (PFCs) � capture some of the energy reflected from the surface of the earth, keeping it in our atmosphere and warming the planet. Second, aerosols - miniscule particles suspended in the air - primarily have a cooling effect on the Earth because they reflect solar radiation back into space before reaching the atmosphere, though aerosols like black carbon produced from burning of biomass and diesel engine exhaust have a warming effect.

The impacts of human activities, however, are now outpacing the long-term, natural climate variabilities. Dating back to the agricultural revolution of the 18th century, human activities have released greenhouse gases and aerosols into the atmosphere, but the amount of these emissions were at a small scale compared to the natural greenhouse gas process. It was not until the turn of the 20th century and the Industrial Revolution that emissions from our actions increased dramatically, trapping more greenhouse gas emissions and in turn more heat in the atmosphere and causing human-induced climate change.

Temperature change map
Global and continental temperature change. Source: IPCC. Click to enlarge.

Greenhouse gases

The concentration of CO2 in the atmosphere reached 384 part per million (ppm) in 2007, an increase of over 30% from pre-industrial levels of 280 ppm over a century ago and far beyond the natural range of concentrations over the last 650,000 years. The latest estimates of emissions in 2004 produced by human activity, or �anthropogenic� emissions, totaled 49 gigatonnes of carbon dioxide equivalent (GtCO2eq), a nearly 25 per cent increase from 1990 levels of 39.4 GtCO2eq. Carbon dioxide is the predominant global greenhouse gas, making up over 75 per cent of total emissions, and is used as a baseline of comparison for other greenhouse gases.

Changes in greenhouse gases
Changes in greenhouse gases from ice core and modern data. Atmospheric concentrations of CO2, methane and nitrous oxide over the last 10,000 years (large panels) and since 1750 (inset panels). Source: IPCC.

Anthropogenic CO2 emissions are mainly a result of fossil fuel combustion, flaring (burning) of natural gas which is a byproduct of oil drilling, and cement production. The energy supply sector, which ranges from fuel mining to energy delivery to the end-user, contributes over 25 per cent of total world emissions. Industry emissions, which include both energy use and industrial processes, follow at 19 per cent, and the forestry sector which includes forest management, forest harvesting for residential and commercial uses, deforestation, afforestation, and forest biomass for bioenergy, at 17 per cent.

The agricultural and transport sector each produce 13 per cent of emissions. Agriculture is the main contributor of methane and nitrous oxide emissions. The methane results from biomass decomposition, the digestion process of livestock like cows, and rice grown in flooded fields. Chemical reactions in the soil and manure due to excess nitrogen emit nitrous oxide. Methane has a potency, or global warming potential, of about 25 times that of carbon dioxide over a 100 year period as a greenhouse emission, and nitrous oxide as a global warming potential of 298.

Global emissions
Share of global emissions in CO2 equivalent, 2004. Source: State of the World 2009, Worldwatch Institute

Climate changes

Since 1901, the Earth has warmed over 0.7�C. Warming in our future is heavily dependent on our actions in the short and mid-term. Even if emissions are capped at 2000 levels, an average temperature increase of 0.1�C per decade is already underway due to the time lag between the initial emitting of greenhouse gases, the subsequent changes in the atmosphere, and the continued self-amplifying processes which feed into other processes, called positive feedbacks.

Anthropogenic emissions are destabilizing the Earth�s climate system. This is directly affecting air and ocean temperature, precipitation and extreme weather events, and creating positive feedbacks in the climate. For example, with more heat trapped in the atmosphere, global average air and ocean temperatures will rise, leading to a positive feedback in which one change results in another process altering the climate in a similar direction - further melting ice and snow both on land and at sea, raising the sea level, and causing other ecosystem changes. The complexity of the climate system also includes dampening, negative feedbacks. Another example, with warmer air temperatures, more water will evaporate and enter the atmosphere, resulting in more clouds. This in turn increases the albedo, or the atmospheric reflectivity, of the Earth and reduces the amount of solar radiative energy absorbed.

This 0.1�C warming will thus occur regardless of our actions. A recent study found that the effects of climate change are largely irreversible, with impacts from carbon dioxide lasting more than 1,000 years. While current and future actions to reduce emissions will not deter the 0.1�C warming, they can prevent further warming. The threshold, or tipping point, of no return, in which the world is catapulted into catastrophic climate change, is generally understood based on science to occur at a 2�C increase over pre-industrial temperatures; however, as emissions continue rising, the world will pass other thresholds, triggering a domino effect of significant and adverse changes in the climate. Avoiding catastrophic climate change is an imperative, but changes even close to catastrophic do not bode well for the world either.

weakened animals
People bringing their weakened animals to an Oxfam destocking programme. Photo: Jane Beesley, Oxfam.

The number of cold days and cold nights in most of the world has a 90 per cent likelihood of decreasing while the number of hot days and hot nights are on the rise. Heat waves will make more regular appearances, as will heavy rainfall which can contribute to flooding. These changes will have asymmetric impacts on regions of the world based on each unique location and ecosystem. Countries further from the equator are expected to experience heavier precipitation, whereas tropical and sub-tropical regions are expected to receive less precipitation.

According to the Intergovernmental Panel on Climate Change (IPCC), an international scientific body established by the World Meterological Organization and UN Environment Programme and responsible for assessing climate change science through consensus, the world could warm by 1.8-4.0�C by 2100. As scientific understanding of the interaction between warming air temperatures and ice sheet melting improve, the possibility of sea level rise reaching one meter is increasing as well.

For reference, all countries with coasts will see changing coastlines of varying levels. Low-lying coastal countries, on the other hand, could witness flooding of large portions of their land. These areas are likely to be heavily populated. For example, one metre of sea level rise in Bangladesh translates into flooding of 14,000-30,000 km2, or 10-20 per cent of its total area, which would displace a fifth of the country�s population. For many small island nations, one metre translates to near to total inundation, requiring complete population migration.

Current impacts

Glaciers and sea ice are already melting at increasing rates. The ice loss of about half a metre during the decade from 1996-2005 is about twice the ice loss during the previous decade and four times the ice loss during the decade before. Coral reefs, an indicator of ocean health and stability due to their sensitivity to warming sea surface temperatures and ocean acidification, are dying off at an alarming rate. The latest review of coral reefs in 2008 found that 20 per cent of the world�s coral reefs had been destroyed or severely damaged. Taking into consideration climate change, all coral reefs are at risk of extinction.

Recent climate-related impacts on land are quite diverse. Three examples are expanding ranges of pests, severe heat waves, and more frequent flooding events. Pine beetles have been moving up in latitude and altitude as regions experience warmer winters and, in taking advantage of already stressed higher temperatures and drought conditions, have had devastating effects on forests. And these forests are important carbon sinks which take up greenhouse gas emissions. In the western United States, nearly 4 million acres of forest were killed in 2007 alone. In Central America, Belize experienced its first ever major pine beetle outbreak in 2000, a natural disaster which had a higher tree mortality rate than any other natural disaster in the country since 1944 when such monitoring began.

Freshwater vulnerabilities
Examples of current vulnerabilities of freshwater resources and their management. In the background, a map of water stress. Source: IPCC. Click to enlarge.

In the last century, some regions of the world (eastern North and South America, northern Europe, and northern and central Asia) saw an increase in precipitation while other regions (the Sahel belt south of the Sahara desert, the Mediterranean region, southern Africa, and parts of southern Asia) saw less � even factoring in natural variables like El Nino and the North Atlantic Oscillation. Europe bore the brunt of extreme weather events in the form of unusually intense flooding in 2002, followed by the heat wave in 2003 which resulted in the deaths of an estimated 30,000 people. In France, the average summer temperature in 2003 was 3.6�C above the long-term norm.

The IPCC agrees that climate change would increase the intensity and severity of extreme weather events, altering what is considered normal for these events. Natural variability has and will continue to play a leading role in these events, but climate changes are expected to exacerbate them. Evidence of this is accumulating globally, as anthropogenic emissions rise, along with the number of weather-related disasters.

Natural hazards like earthquakes are far less susceptible to human influence than weather-related natural hazards like hurricanes, winter storms, flooding, and wildfires. The 1980s saw on average 300 disasters a year of weather-related disasters, and that number grew to 480 in the 1990s, and in the last decade has increased to 620. Meanwhile, worldwide economic losses associated with these disasters topped $214 billion (USD) in 2005 as a result of an intense hurricane season. While climate change does not directly cause these events, destabilizing the climate system will affect � primarily increase � the likelihood and severity of extreme weather events.

Future impacts

Future impacts of climate change on the Earth and human vulnerabilities to those impacts could be numerous. While some regions of the world could experience more annual rainfall, water resources both above and below ground in many regions of the world will also be strained, as precipitation patterns shift. Where glaciers and annual snowmelt are the primary source for surface waters, regions can expect declining water availability over the next 100 years. For example, glaciers in Tibet are the start of six major rivers located in the some of the most heavily populated regions of the world.

Future water vulerability
World map of future water vulnerabilities. Source: IPCC. Click to enlarge.

Indirectly due to climate change, regions reliant on groundwater sources might also experience problems, as water for recharging aquifers dwindles. Additionally, many aquifers are being mined for water at an unsustainable rate. A decline in water resources could create waves of instability in both natural and human systems, impacting agriculture and food security, ecosystems and biodiversity, human health, settlements and infrastructure, the economy, sanitation, and of course the water supply.

In addition to effects on natural systems, like increased run-off or soil erosion, climate change will stress food security in the human system. Agricultural productivity is very sensitive to seasonal heat, and sub-tropical areas are expected to receive much less precipitation. As extremes become the norm by the next century - which has a greater than 90% chance of occurring in the sub-tropics and tropics, vulnerable communities will be hard pressed to achieve or maintain food security. Because climate change affects regions disproportionately, the average temperature during growing season will likely exceed the historic extremes in semi-arid regions like the Sahel.

The task of protecting and improving human health becomes increasingly unwieldy as ranges for vectors that carry diseases like malaria, dengue fever, and schistosomiasis extend further in latitude and altitude to regions that were previously protected by their cold winter conditions. The intensity and seasonality of vector-borne disease outbreaks are projected to change as well.

Global response

The science of climate change is bringing to light an immense challenge for the global community, but climate change can also be considered �breathtaking opportunities disguised as insoluble problems,� in the words of John Gardner, former US Secretary of Health, Education, and Welfare and founder of Common Cause. The global community has two courses of actions that it can � and must � undertake to mitigate the causes of climate change to the best of our abilities as well as to adapt to climate change.

Climate change is happening and will continue to a certain extent regardless of short- and middle-term actions, and adaptation is a necessity for all countries but particularly for the most vulnerable. These developing countries are also struggling with poverty and food insecurity, among others, which combine to worsen climate change vulnerabilities.

Encroaching sands, Sudan
Encroaching sands have displaced entire communities, such as the people of the village of Jadallah. Photo � UNEP

Mitigation actions must be taken in all countries. Developed countries have contributed the majority of historic emissions which have brought the world to where it is now, but many developing countries are catching up in emissions very quickly and some are even surpassing developed country emissions levels. In 2007, China took the lead in total greenhouse gas emissions, displacing the United States.

The world�s response to climate change must be different than its responses to previous environmental problems. In the late 1980s, the global community mobilized to remove ozone-depleting chemicals from common use. Efforts were largely successful, and the ozone holes over the poles began shrinking within in a matter of years. Climate change will require a similar united response but on of a magnitude far greater, and the effects of these efforts will take longer to come to fruition.

In 1970s and 1980s, the scientific community made the link between acid rain and sulphur and nitrogen pollution. Through national and local efforts to limit or eliminate these emissions, people responded to protect their well-being and their living environment. Climate change, however, is not a geographically local problem that can be solved by local or regional efforts alone. Once greenhouse gases are emitted from their sources, they mix into the atmosphere and blanket the entire planet. To address climate change, international efforts must integrate with local, national, and regional abilities.

Under the United Nations Framework Convention on Climate Change (UNFCCC), the Kyoto Protocol aims at the �stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system.� Kyoto was the successful outcome of a difficult process, but agreement on the definition of �dangerous anthropogenic interference� has continued to be the center of much debate. In the Kyoto agreement, countries also acknowledge the �common but differentiated responsibilities� of developed and developing countries which have varying capacities to address climate change. Binding obligations apply only to Annex I countries, primarily industrialized countries, in the first commitment period (2008-2012). These countries agreed to reduce their emissions by 5 per cent by 2012 compared to 1990 levels.

Kyoto also recognized the similar challenge of clean development in developed countries and developing countries, or non-Annex I countries under the UNFCCC. Promoting sustainable development is the underlying goal behind the three �flexible mechanisms� under Kyoto (emissions trading, joint implementation, and clean development mechanism).

In 2007, the global community began serious preparations towards a new climate change agreement for the second commitment period of the Kyoto Protocol in Bali, Indonesia (COP13). Those efforts continued at the Conference of Parties in Poznan, Poland (COP14) and are to culminate at the Conference of Parties in Copenhagen, Denmark (COP15) in December of 2009.

The 2007 �Bali Roadmap� framed the plan of action for the 183 signatories of the UNFCCC. Among the outcomes of COP13 are agreements to incorporate �measurable, reportable, and verifiable� and nationally appropriate mitigation efforts by developed countries into the Copenhagen agreement. In a big shift, developing countries signalled a new willingness to engage in mitigation in addition to adaptation. Thus �measurable, reportable, and verifiable� mitigation efforts by developing countries will also be considered.

The results of COP14 in Poznan raised concerns that the Copenhagen agreement was in jeopardy, with only the bare minimum agreed upon by the end of the two week conference. The European Union, normally a leader in this arena, was embroiled in debates on its own climate change package (20-20 by 2020), and the United States (and the world) was waiting for the inauguration of its next President, leaving a leadership vacuum in the UNFCCC process. Developing countries tried to improve the productivity at COP14 with a few notable proposals, but at COP15, both developing and developed countries must be actively engaged.

If the world is to limit global warming to 2�C, it must reduce emissions by 50 to 80 per cent compared to 2000 levels by 2050, according to the IPCC. Scientists, vulnerable countries, and others are increasingly calling for a warming limit of 1.5�C. Calling the 2�C target �suicide� for small island nations, Selwin Hart � a representative from Barbados at COP14 � stated on behalf of the Alliance of Small Island States (AOSIS), �agreeing to a goal that results in our extinction is not something we�re prepared to do.� There is much need to prevent further changes in the climate, and with world emissions steadily increasing, there is still much to be done.

Amanda Chui is a Sustainable Energy Fellow at the Washington-based Worldwatch Institute, with a special interest in energy and climate change research.

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