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Keeping Climate Liveable

Windmills at the coastline
Bar chart: 154 000 deaths per year, 182 million lives at risk Bar chart: 83 billion $ in damages per year, 5-20% of per-capita consumption at riskNegative trend

Man-made climate change will likely include the ongoing increase of global surface temperature, as well as increasing thermal extremes and weather disasters, affecting agricultural crops and biodiversity, rainfall and freshwater supplies, sea-levels, changes in the dynamics of disease vectors, etc. (and so on)

Affected people and foundations of life: Climate change affects the entire world population, especially those in coastal zones and less developed countries.

Global surface temperature has already risen in the 100-year linear trend (1906-2005) by 0.74°C (degree Celsius) [0.56 to 0.92°C] (IPCC [Intergovernmental Panel on Climate Change] 2007, 1). Ten of the last twelve years (1996-2007) rank among the twelve warmest years in the instrumental record of global surface temperature (since 1850; WMO [World Meteorological Organization] 2008, 4). Sea level has risen during the 20th century by 0.17m (metre) [0.12 to 0.22m] (IPCC 2007a, 7). Arctic sea ice extent has shrunk per decade by 2.7% [2.1 to 3.3%], observed by satellites since 1978. By a probability of more than 66%, the area affected by drought has enlarged since the 1970s, the frequency of heat waves and heavy precipitation events have increased over most areas, and the incidence of weather-related extreme high sea level has increased worldwide. (IPCC 2007, 1.) In terrestrial ecosystems, earlier timing of spring events and poleward and upward shifts in plant and animal ranges are with very high confidence linked to recent warming (IPCC 2007, 2).

Most of the rise in global temperatures since the mid-20th century is, by probability of more than 90%, due to the increase in man-made greenhouse gas concentrations (IPCC 2007, 5). There is very high confidence that the net effect of human activities since 1750 has been one of warming. Increasing greenhouse gases tend to warm the surface while increases of aerosols tend to cool it. The net effect is one of warming (+1.6W/m2 [watts per square metre) [+0.6 to +2.4W/m2]). There is an additional, but ten times smaller warming effect caused by natural changes in solar radiation (+0.12W/m2 [+0.06 to +0.30W/m2]). (IPCC 2007, 4f. [and following page])
  Global atmospheric concentrations of major greenhouse gases – carbon dioxide, methane and nitrous oxide – have increased substantially as a result of human activities since 1750 and now exceed pre-industrial levels by far. Global greenhouse gas emissions due to human activities have grown since pre-industrial times. From 1970 to 2004, emissions increased from 28.7 billion tonnes of CO2-equivalent to 49.0 billion tonnes CO2-eq (carbon dioxide equivalent). Carbon dioxide (CO2) is the most important greenhouse gas, accounting by fossil fuels for 56.6%, and by deforestation and decay of biomass for 17.3% of man-made greenhouse gas emissions. The portion of methane (CH4) is 14.3%, the one of nitrous oxide (N2O) 7.9%. The life-time of CO2 within the atmosphere is 50-200 years. Sectors that are most responsible for global greenhouse gas emissions are energy supply (25.9%), industry (19.4%), deforestation and forestry (17.4%), agriculture (13.5%), and transport (13.1%). (IPCC 2007, 4.)

With current climate change mitigation policies and related sustainable development practices, global greenhouse gas emissions will continue to grow over the next decades. This would cause further warming trends and induce many changes in the global climate system. For the next two decades a global warming of about 0.2°C per decade is projected for a range of emission scenarios. Afterwards, temperature projections depend increasingly on specific emission scenarios, as shown in table 1. (IPCC 2007, 6.)

Table 1:
IPCC TAR Scenarios on Greenhouse Gas Emissions
(Source: IPCC 2007, 7, table SPM.1.)
IPCC TAR Scenarios
(in the absence of climate policies above current level)
CO2-equivalent concentration
(at 2090-99, GHGs and aerosols)
Temperature change
(at 2090-99 relative to 1980-99)
Sea level rise
(at 2090-99 relative to 1980-99)
B1 (global sustainability) 600 ppm (parts per million) +1.8°C [1.1-2.9°C] 0.18-0.38m
A1T (business as usual + non-fossil energy) 700 ppm +2.4°C [1.4-3.8°C] 0.20-0.45m
B2 (local sustainability) 800 ppm +2.4°C [1.4-3.8°C] 0.20-0.43m
A1B (business as usual + balancing fossil and non-fossil) 850 ppm +2.8°C [1.7-4.4°C] 0.21-0.48m
A2 (regional fragmentation) 1250 ppm +3.4°C [2.0-5.4°C] 0.23-0.51m
A1Fl (business as usual + fossil energy) 1550 ppm +4.0°C [2.4-6.4°C] 0.26-0.59m

The data on sea level rise does not fully include feedbacks in the climate-carbon cycle and also changes in ice sheet flow, both of which might increase. (IPCC 2007, 7f.) Thermal expansion of sea water would continue for many centuries, even after greenhouse gas concentrations have stabilized (IPCC 2007, 21).
  Climate change will have negative impacts on all global regions (IPCC 2007, 8-11). A global temperature rise of more than 1.5-2.5°C (0.15-0.25°C per decade) could cause major impacts in the sectors of water availability, food, health, ecosystems, and coastal systems (IPCC 2007, 9). Moreover, anthropogenic warming could lead to some impacts that are abrupt or irreversible, depending on the rate and magnitude of the climate change. Partial loss of ice sheets on polar land could imply metres of sea level rise, major changes in coastlines and inundation of low-lying areas, with greatest effects in river deltas and low-lying islands. There is medium confidence that approximately 20-30% of species assessed so far are likely to be at increased risk of extinction if increases in global average warming exceed 1.5-2.5°C (relative to 1980-1999). As global average temperature increase exceeds about 3.5°C, model projections suggest significant extinctions (40-70% of species assessed) around the globe. (IPCC 2007, 13.) Avoiding a global temperature rise above 1.5-2.5°C requires stabilization of greenhouse gas emissions by 2015 at the latest, as table 2 indicates.

Table 2:
Characteristics of post-TAR stabilization scenarios
(Source: IPCC 2007, 21, table SPM.6.)
Category CO2-equivalent Concentration at stabilization including GHGs and aerosols (2005 = 375 ppm) Peaking year for CO2 emissions Change in global CO2 emissions in 2050 (% of 2000 emissions) Global average temperature increase above pre-industrial at equilibrium, using "best estimate" climate sensitivity Global average sea level rise above preindustrial at equilibrium from thermal expansion only Number of assessed scenarios
ppm year % °C metres
I445-4902000-2015-85 to -502.0-2.40.4-1.46
II490-5352000-2020-60 to -302.4-2.80.5-1.718
III535-5902010-2030-30 to +52.8-3.20.6-1.9 21
IV590-7102020-2060+10 to +603.2-4.00.6-2.4 118
V710-8552050-2080+25 to +854.0-4.90.8-2.9 9
VI855-11302060-2090+90 to +1404.9-6.11.0-3.7 5

Mitigation of climate change can benefit other issues like lowering pollution and maintaining biodiversity. A stabilization at 450 ppm CO2-eq leads to reductions in the range of 20-30% for sulphur oxide emissions (SOx) and 30-40% for nitrogen oxides (NOx). (OECD [Organisation for Economic Co-operation and Development] 2008, 163 and 165.) On the other hand, climate change could impede achievement of the Millennium Targets (IPCC 2007, 18f.; referring to UN [United Nations] 2000).
  The economic cost of disasters associated with climate change reached US$ (United States dollar) 83 billion in 2005 (insured losses from tropical cyclones in the North Atlantic; Munich Re 2006, 4, 7 and 13). According to the report by Sir Nicholas Stern, most earlier studies on the cost of climate change tended not to include some of the most uncertain but potentially most damaging impacts (Stern 2006, 143). Considering them, climate change could create risks of major disruption to economic and social activity, later in this century and in the next, on a scale similar to those associated with the great wars and the economic depression of the first half of the 20th century (Stern 2006, ii [roman 2]). In a temperature range of 2-3°C warming, the cost of climate change could be equivalent to a 0-3% loss in global GDP (gross domestic product). Poor countries will suffer higher costs. Regarding the total cost of climate change occurring by business as usual (higher warming), and expressed in terms of reduction in current per-capita consumption … the appropriate estimate of damages may well lie in the upper part of the range 5-20%. (Stern 2006, 143.) According to a similar estimate the total damage costs in 2050 and 2100 will represent 20% to 23% of global GDP, respectively, if no climate policies will be introduced (Kemfert/Schumacher [DIW (Deutsches Institut für Wirtschaftsforschung)] 2005, 35; OECD 2008, 281).

A linear climate change is considered to be a risk with quite a high extent of damage and quite a high probability of occurrence; non-linear changes (e. g. [for example] destabilization of ice sheets) have a higher extent of damage but unknown probability (WBGU [German Advisory Council on Global Change] 1998, 62).


  • 154 000 death cases in 2000, with increasing numbers in the future, are attributed to climate change (WHO [World Health Organization] 2002, 72, and 2004a, 1544f.).
  • By the end of this century, an estimated total of 182 million people in sub-Saharan Africa may have been killed by diseases associated with climate change in case of the IPCC's worst-case scenario of the Earth's temperature rising by 6°C by 2100 (Christian Aid 2006, 9).

Loss of healthy life-years: 5.5 million healthy life-years in 2000, with increasing numbers in the future (DALYs [Disability-adjusted life years], attributable to climate change; WHO 2002, 72, and 2004a, 1544f., 1607).


  • 192 countries have agreed to the objective of stabilization of greenhouse gas concentrations in the atmosphere at a level that would prevent dangerous anthropogenic interference with the climate system (UNFCCC [United Nations Framework Convention on Climate Change] 1992, § 2).
  • 40 industrialized countries and countries in transition to market economies have agreed on the aim of returning individually or jointly to their 1990 levels these anthropogenic emissions of carbon dioxide and other greenhouse gases (Annex I parties, UNFCCC 1992, § 4.2b).
  • 38 industrialized countries and countries in transition have committed themselves to reduce their greenhouse gas emissions from 1990 to 2008-12 by 5% (Kyoto Protocol,
  • The European Union (27 member states) is committed to achieve at least a 20% reduction of greenhouse gas emissions by 2020 compared to 1990. Moreover, it endorses an EU objective of a 30% reduction in greenhouse gas emissions by 2020 compared to 1990 as its contribution to a global and comprehensive agreement for the period beyond 2012, provided that other developed countries commit themselves to comparable emission reductions and economically more advanced developing countries to contributing adequately according to their responsibilities and respective capabilities. (EU [European Union] 2007, 12.). The EU also underlines the vital importance of achieving the strategic objective of limiting the global average temperature increase to not more than 2°C above pre-industrial levels (EU 2007, 10).
  • Many scientists demand halving global emissions by 2050. Concerning this the G8 (Group of Eight industrialized countries) stated: We seek to share with all Parties to the UNFCCC the vision of, and together with them to consider and adopt in the UNFCCC negotiations, the goal of achieving at least 50% reduction of global emissions by 2050, recognizing that this global challenge can only be met by a global response, in particular, by the contributions from all major economies, consistent with the principle of common but differentiated responsibilities and respective capabilities. In order to ensure an effective and ambitious global post-2012 climate regime, all major economies will need to commit to meaningful mitigation actions to be bound in the international agreement to be negotiated by the end of 2009. (G8 2008, §§ 23 and 24).


  • Worldwide: increase by 24.4% in greenhouse gas emissions, from 39.4 billion tonnes CO2-eq in 1990 to 49.0 billion tonnes CO2-eq in 2004 (IPCC 2007, 4). Carbon dioxide emissions by fossil fuels increased by 30%, from 21.3 billion tonnes in 1990 to 27.7 billion tonnes in 2005 (UN 2008, 37, and 2008a, indicator 7.2a; 2005 preliminary data). Most of this increase comes from emerging economies, and industrialized countries.
  • Annex I parties of UNFCCC (40 countries): reduction by 4.7% in greenhouse gas emissions from 1990 to 2006, with a slight increase since 2000
    • economies in transition: reduction by 37.0%
    • industrialized countries: increase by 9.9%
    (excluding emissions from land use, land-use change and forestry; UNFCCC 2008, part 1).
  • Parties of the Kyoto Protocol (38 countries): reduction by 17.2% in greenhouse gas emissions in 2006, compared to 1990
    • economies in transition: reduction by 37.1%
    • industrialized countries: increase by 0.9%
    (excluding emissions from land use, land-use change and forestry; UNFCCC 2008, part 2).

Measures: There is high confidence that neither adaptation nor mitigation alone can avoid all climate change impacts; however, they can complement each other and together they can significantly reduce the risks of climate change. … Mitigation efforts and investments over the next two to three decades will have a large impact on opportunities to achieve lower stabilisation levels. Delayed emission reductions significantly constrain the opportunities to achieve lower stabilisation levels and increase the risk of more severe climate change impacts. (IPCC 2007, 20.)

Economic potential for the mitigation of global greenhouse gas emissions over the coming decades is sufficient to offset the projected growth of global emissions or reduce emissions below current levels (IPCC 2007, 14). Net additional investment required ranges from negligible to 5-10% (IPCC 2007, 18). An effective carbon-price signal could realize significant mitigation potential in all sectors. Global carbon prices rising to 20-80 US$ per tonne CO2-eq by 2030 would be appropriate for stabilization at around 550ppm CO2-eq by 2100 (corresponding to scenario B1 in table 1). Induced technological change may lower these price ranges to 5-65 US$/tCO2-eq in 2030. (IPCC 2007, 18.)
  In 2050, global average macro-economic costs for mitigation towards stabilization between 710 and 445ppm CO2-eq are between a 1% gain and 5.5% decrease of global GDP. This corresponds to slowing down average annual global GDP growth by less than 0.12%. (IPCC 2007, 22f.) An OECD estimate indicates that a stabilization at 450ppm CO2-eq would cause manageable costs of 2.5% of global GDP below baseline estimate in 2050, equivalent to 0.1% reduction in annual GDP growth (OECD 2008, 25, 140 and 166). Early analytical results from integrated analyses of the costs and benefits of mitigation indicate that they are broadly comparable in magnitude (IPCC 2007, 22f.). According to the Stern Review, the benefits of strong, early action considerably outweigh the costs (Stern 2006, ii). About half the costs of greenhouse gas reduction required by the Kyoto Protocol might be recovered from air pollution control costs (co-benefits; OECD 2008, 163).

Appropriate measures should be intensified, including climate protection and adaptation efforts such as: strengthening energy efficiency, energy saving and renewable energies, emissions trading or carbon/energy tax, plane ticket tax, forest preservation and afforestation, sound agriculture, technology transfer, protection of coastal zones, public health, etc. Inter alia, the Asia-Pacific Partnership on Clean Development and Climate (7 developed and less developed countries) fosters the development and deployment of clean energy technologies by action plans and over 100 related projects ( Pertaining to environmental and clean energy technology research and development (R&D), ... G8 members have so far pledged over the next several years over US$ 10 billion annually in direct government-funded R&D. The G8 also pledged approximately US$ 6 billion to climate related funds supporting less developed countries. (G8 2008, §§ 31 and 32). An international agreement on emissions reductions, that comes into effect after the expiration of the Kyoto target (2012), should be negotiated and ratified timely.


Numbers in square brackets indicate a 90% uncertainty interval around a best estimate (IPCC 2007, 1).

1 tonne = 1 000 kg = 1 metric ton.

For numeric names the short scale is used:
1 billion = one thousand million = 109 = 1 000 000 000

DALYs: Disability-adjusted life years.
One DALY represents the loss of one year of equivalent full health. DALYs are the sum of the years of life lost due to premature mortality (YLL) in the population and the years lost due to disability (YLD) for incident cases of the health condition. (WHO 2004, 95f.)


Draft (2008)

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Photo credit: © BMU/H.-G. Oed